Survey on Blockchain based Smart Contracts: Applications, Opportunities and Challenges

Abstract

Blockchain is one of the disruptive technical innovation in the recent computing paradigm. Many applications already notoriously hard and complex are fortunate to ameliorate the service with the blessings of blockchain and smart contracts. The decentralized and autonomous execution with in-built transparency of blockchain based smart contracts revolutionize most of the applications with optimum and effective functionality. The paper explores the significant applications which already benefited from the smart contracts. We also highlight the future potential of the blockchain based smart contracts in these applications perspective.

Full text

Survey on Blockchain based Smart Contracts: Applications, Opportunities and Challenges
Tharaka Hewa
Center for Wireless Communications, University of Oulu, Finland
Mika Ylianttila
Center for Wireless Communications, University of Oulu, Finland
Madhusanka Liyanage
School of Computer Science, University College Dublin, Ireland
Center for Wireless Communications, University of Oulu, Finland
Abstract
Blockchain is one of the disruptive technical innovation in the recent computing paradigm. Many applications already notoriously
hard and complex are fortunate to ameliorate the service with the blessings of blockchain and smart contracts. The decentralized
and autonomous execution with in-built transparency of blockchain based smart contracts revolutionize most of the applications
with optimum and effective functionality. The paper explores the significant applications which already benefited from the smart
contracts. We also highlight the future potential of the blockchain based smart contracts in these applications perspective.
Keywords: Blockchain, Smart Contracts, Applications, DLT, Hyperledger Fabric, Ethereum, Corda, Stellar
1. Introduction
The blockchain is a decentralized, distributed and immutable
ledger comprised of a cryptographically linked chain of record
collection. The collection of records referred as blocks and the
records called transactions or events. The decentralized ledger
is shared within all contributory members in the blockchain
network. These transactions add to the ledger upon verifica-
tion and agreement process between the parties on-board in the
blockchain. The important features associated with blockchain
are the decentralization, immutability and cryptographic
link.
Decentralization:The decentralization of blockchain dele-
gate the authority among the contributors of the network. It
is a distinction of the blockchain which ensure redundancy in
contrast with the centralized systems operated by a trusted third
party. The decentralization ensures the service availability, re-
duce the risk of failure and eventually improve the trust of ser-
vice with guaranteed availability.
Immutability: The records of transactions in the ledger,
which remain distributed between the nodes are permanent and
unalterable. The immutability is a distinguishing feature of the
blockchain from the centralized database systems which ele-
vates to the next level for the integrity of data on the ledger.
Email addresses: tharaka.hewa@oulu.fi (Tharaka Hewa),
mika.ylianttila@oulu.fi (Mika Ylianttila), madhusanka@ucd.ie
(Madhusanka Liyanage)
The records are computationally tamper resistant with the exis-
tence of the cryptographic links.
Cryptographic Link: The cryptographic link between each
record sorted in the chronological order and the block builds the
chain of integrity in the entire blockchain. The digital signature
verifies the integrity of each record using hashing techniques
and asymmetric key cryptography. The alteration of block or
transaction record violate the integrity and eventually make the
record and block invalid.
In addition, cryptocurrencies enable seamless peer to peer
payments and proliferate the financial context accentuating as
the first generation of blockchain to the world. Cryptocurren-
cies are virtual and digital currencies secured with digital sig-
natures. Bitcoin [1] is the first prominent cryptocurrency in
the world which enables the peer-to-peer financial transactions
without the intervention of trusted third party such as interna-
tional payment channels. The system operates without a third
party and the transactions committed to the network are veri-
fied by dedicated nodes called miners using the cryptographic
techniques.
1.1. Significance of Blockchain based Smart Contracts
Smart contracts are self-enforcing and self-executing pro-
grams which actuate the terms and conditions of a particular
agreement or contract using software codes and computational
infrastructure. Buterin et al. [2] instigated the concept of smarts
contract emphasizing the key features with the inaugural de-
ployment in the financial industry. The smart contracts are an
Preprint submitted to Journal of Network and Computer Applications September 21, 2020

Table 1: Summary of Important Acronyms
Acronym Definition
3D 3 Dimensional
5G 5th Generation
ADS-B Automatic Dependent Surveillance – Broadcast
AI Artificial Intelligence
AIRA Autonomous Intelligent Robot Agent
API Application Programming Interface
AU Application Unit
BFT Byzantine Fault Tolerance
BTO Basic Timestamp Ordering
CA Certification Authority
CBRS Citizens Broadband Radio Services
COAP COnstrained Application Protocol
CVV Card Verification Value
DAML Digital Asset Modeling Language
dApp Distributed Applications
DDOS Distributed Denial of Service
DEX Decentralized Exchange
DLT Distributed Ledger Technology
eGovernment Electronic Government
ERC Ethereum Request for Comment
FAO Food and Agricultural Organization
FSM Finite State Machine
EV Electric Vehicle
EVM Ethereum Virtual Machine
FBI Federal Bureau of Investigation
GDPR General Data Protection Regulation
HIPAA Health and Information Privacy and Portability
Act
HDG Health Data Gateway
HSM Hardware Security Module
IAM Identity and Access Management
ICO Initial Coin Offering
IoT Internet of Things
IT Information Technology
KYC Know Your Customer
LDAP Lightweight Directory Access Protocol
LORA LOng RAnge
MAC Medium Access Control
ML Machine Learning
MNO Mobile Network Operator
NFT Non Fungiable Token
OBU On Boarding Unit
PBFT Practical Byzantine Fault Tolerent
PA-DSS Payment Application-Data Security Standards
PCI-DSS Payment Card Industry-Data Security Standards
PKI Public Key Infrastructure
PoS Proof of Stake
STM Software Transactional Memory
UAV Unmanned Aerial Vehicles
VR Virtual Reality
UTXO Unspent Transaction Output
WAN Wide Area Network
WBAN Wireless Body Area Network
extension of the utilization of distributed ledger. The smart con-
tract operates as decentralized programs on the blockchain net-
work. The program is immutable and cryptographically verified
the immutability to ensure the trust of the program. The key fea-
tures of the smart contracts are execution in peer to peer mode
without the intervention of a centralized third party and ser-
vice availability without any centralized dependency. The au-
tonomous execution aligned to the predefined conditions makes
the contracts smart rather than paper condition.
The smart contracts’ features enable the pertinence of them
to diverse domains. Many of such features inherited from
the underlying blockchain technology. The key features of
blockchain based smart contracts can be categorized as follows.
1.1.1. Elimination of Trusted Third Party
The blockchain is capable to operating in collaboration with
decentralized nodes. The smart contracts enable autonomous
execution within predefined conditions. These are the key fea-
tures to resolve most of the limitations in centralized applica-
tions. The decentralization eradicates the single point of fail-
ure which ensures the ceaseless service availability. The de-
centralization also eliminates the extensive data consumption
and latency in operations when comparing with the round trip
requests of the centralized systems. The decentralization pro-
vides transparency in the computational logic eliminating the
centralized ”Black Box” concept transferring the accountabil-
ity to all the members.
1.1.2. Forge Resistance
The integrity of each transaction and block in the distributed
ledger verified with the digital signatures. The forge resistance
is a key distinguishing feature which augments the value of
blockchain. The transaction record and the computational logic
of execution are cryptographically verified and remain persis-
tently over the network.
1.1.3. Transparency
Transaction transparency is another significant benefit of
blockchain based smart contracts. The blockchain ledger and
smart contract logic is visible to all parties in the blockchain
ecosystem. The transparency is a differentiating feature of
the blockchain which makes it lucrative among the centralized
databases.
1.1.4. Autonomous Execution
The programmed condition and flow of events defined to ac-
complished execute once the blockchain system reached to the
triggering state. The triggering state can be defined in the smart
contract upon agreement of all parties in the blockchain net-
work. It can be any condition such as reduced funds, a node
reaches a particular geographical location or the system re-
ceives a payment. The significant feature is that the execution
is automatic and triggered on a condition of the peer without
intervening a centralized third party. The service availability is
guaranteed since the operation does not rely on a centralized
third party.
2

1.1.5. Accuracy
The programmed conditions in the smart contracts are im-
mutable and verified prior to the deployment in nodes in the
blockchain network. The execution is automatic once the con-
dition is met. The accuracy is guaranteed without any human or
any other error on the execution. The autonomous accurate ex-
ecution eliminates the biased operation and improves the trust
through transparent accurate execution.
1.2. Paper Motivation
The smart contracts facilitate the enforcement of contractual
agreements with in-built transparency and forge resistance. The
distinguishing features of smart contracts make it pertinent into
many applications. A lot of research conducted in the industry
as well as academia in order to investigate the strengths and ap-
plicability of smart contracts in different application domains.
Furthermore, the improvements of technical aspects highly fo-
cused to fine tune the smart contracts for the enhancement of
compatibility of the smart contracts. There are many smart
contract platforms emerging in the market with associated dis-
tinguishing features which suits for specific applications.
Wang et al.[3] provided a comprehensive overview of
blockchain-powered smart contracts spotting the distinguished
challenges in the smart contracts along with future trends.
Wright et al. [4] presented the benefits and drawbacks of the
emerging decentralized technology and its requirement to the
expansion of a new subset of law that termed as Lex Cryp-
tographia and highlighted the requirement of the regulation of
blockchain-based smart contract based organizations under le-
gal theory. Udokwu et al. [5] provided a systematic review of
previous studies such as frameworks, simulations, methods and
working prototypes that demonstrated the application of smart
contracts in the organization along with the main anticipations
of smart contracts in the enterprise including the establishment
of the trust. Seijas et al. [6] provided a high-level overview of
the scripting languages utilized in the existing cryptocurrencies
and smart contract platforms including Ethereum, Bitcoin and
Nxt highlighting the strengths and weaknesses.
Aggrawal et al. [7] presented a comprehensive in-depth anal-
ysis in the smart community context with a comparative anal-
ysis with existing survey. W ¨
ust et al. [8] critically analyzed
the applicability of blockchain for a particular application sce-
nario proposing a structured methodology to determine the rel-
evant technical solutions and evaluated with some significant
real-world applications. Clack et al. [9] explored the design
landscape of potential formats for storage and transmission of
smart legal agreements in association with blockchain tech-
nology specifically for the financial services context. Chen et
al. [10] modeled smart contract execution over a decentralized
network over an agent-based framework and introduced novel
concepts including penalties and incentives to the agent-based
model. Sousa et al. [11] proposed a Byzantine Fault-Tolerant
(BFT) ordering service for ordering verified transactions in the
Hyperledger Fabric with a novel consensus approach with suc-
cessful results yielded. Xu et al.[12] proposed a classification
method and compared blockchain and blockchain-based sys-
tems to assist with the design and assessment of their impact
on software architecture. The significant design patterns of the
blockchain also discussed in the paper. Marino et al. [13] devel-
oped a set of standards that enabled the smart contracts to alter
or undo a contract made and conveyed its significance with ap-
plying on Ethereum smart contracts platform.
Norta et al. [14] illustrated the existing problems associated
with non-machine readable classical contracts entirely based
on trust. Luu et al. [15] proposed SMARTPOOL which is a
novel protocol design for a decentralized mining pool. The au-
thors implemented and deployed SMARTPOOL on Ethereum
and Ethereum classic networks with constructive experimental
results. Dai et al. [16] proposed Qtum-framework for a novel
smart contract and blockchain-technology solution which uses
Proof-of-Stake (PoS) validation. The framework aligned to the
Unspent Transaction Output (UTXO) model which used in Bit-
Coin. In contrast with Ethereum’s account-based model since
they highlighted that Ethereum’s account-based model has scal-
ability limitations.
Macrinici et al. [17] presented the problems and correspond-
ing solutions in a broader perspective along with the research
trends relevant to the blockchain based smart contract context
and highlighted that the immature state of smart contracts. The
authors also itemized the security, privacy, scalability, and pro-
grammability of the smart contracts highly focused in the con-
ducted research previously. Zheng et al. [18] presented a sur-
vey on challenges and opportunities in blockchain. He et al.
[19] presented survey on blockchain technology and its appli-
cation prospect. Sankar et al. [20] focused on analyzing con-
sensus protocols proposed with their feasibility and efficiency
in the properties they proposed to facilitate for the significant
blockchain platforms like Hyperledger Fabric, Stellar and R3
Corda. Singh et al. [21] presented the significance of the con-
cept of sidechain, with a review upon examination, which has a
future potential in blockchain context.
1.3. Our contribution
The best of our knowledge, there is no single survey which
considered the application of blockchain based smart contracts
in broader and deeper perspective. Thus, this survey conduct
with a deep focus on the applications of blockchain based smart
contracts. The contribution of the survey include,
•Background of blockchain based smart contracts :
An informative overview on the blockchain based smart
contracts highlighting the core principles utilized in the
blockchain.
•Importance of blockchain based smart contracts: The
key features of blockchain based smart contracts which
distinguish blockchain based architecture.
•Overview on significant blockchain platforms: The well
known blockchain platforms with their key features dis-
cussed along with the real world applications.
•Application domains of blockchain based smart con-
tracts: A broad illustration on each application domains
of blockchain based smart contracts with related works,
which is the core content of the survey.
3

Table 2: Previous Surveys on Smart Contracts
Ref Description Comparison with our contribution
[17] Smart contract applications within blockchain technology: A sys-
tematic mapping study: A systematic study which presents problems,
corresponding solutions, and the research trends including numerical
figures in a broader perspective.
Discussed the smart contracts and their
role in concrete application perspec-
tive, identifying the application specific
insights.
[22] An Empirical Analysis of Smart Contracts: Platforms, Applica-
tions, and Design Patterns: The usage of smart contracts analyzed
on different platforms. There were 834 smart contracts analyzed by
categorizing into their application domain.
The role of smart contracts analyzed
distinguishing by the application do-
mains.
[23] A Comprehensive Survey on Attacks, Security Issues and
Blockchain Solutions for IoT and IIoT:A broad and comprehensive
discussion on the blockchain solutions in the IoT and IIoT security con-
text.
We discussed the smart contracts in the
application perspective.
[24] A Survey on Privacy Protection in Blockchain System: A compre-
hensive survey on the privacy protection including identity manage-
ment.
We discussed the smart contracts
mostly focusing in the applicability.
[25] Applications of Distributed Ledger Technologies to the Internet of
Things: A Survey: The applicability of smart contracts in different
contexts along with IoT discussed including the challenges and future
research issues.
We considered application contexts not
limited to the IoT intervention.
[26] A Survey of Blockchain Applications in Different Domains : An in-
formative and brief high level survey on the blockchain for different
application contexts including financial and healtchare.
We focused in detailed into the differ-
ent sub contexts on each application
and the associated issues with signifi-
cant number of related works.
[27] Blockchain: A Survey on Functions, Applications and Open Is-
sues:Presents an analysis of blockchain and their applications along
with different open issues.
We focused deeply on the application
of blockchain.
[28] Blockchain and Its Applications – A Detailed Survey : A high level
discussion on blockchain and its applicability on different contexts.
We discussed in detail on the each ap-
plication context.
•Technical challenges and solutions of smart contracts:
A high-level review on the significant challenges of smart
contracts when they are applying to the real world use
cases. Furthermore, a review on the corresponding solu-
tions included as an elaboration.
•Lessons learned and future works: The insights of cur-
rent applications and the future improvements required to
address the existing issues of them discussed.
•Future applications: The application domains which
have a potential in applicability of blockchain based smart
contracts in future.
1.4. Outline of the Paper
The rest of the paper is organized as follows. Section 2
provides a brief introduction to the paper with background in-
formation applicable to the smart contracts. The important
acronyms with the definitions included in Table 1. A summary
of important surveys related to the paper presented in Table 2.
Table 3 projects the smart contract platforms with pointers to
applications of current use. The different application contexts
discussed in the Section 3. The Section 4 includes a review
on the key technical challenges encountered in the smart con-
tracts. The Section 5 discusses the lessons learned and future
work. Section 6 concludes the survey.
2. Different Smart Contract Platforms and Their Applica-
tions
Smart contracts can transform the business rules into the
computer programs. Different smart contract platforms have
developed to address specific requirements in each industry.
Each smart contract platform includes a set of specific fea-
tures targeted to the particular application. For an instance,
Ethereum is mainly developed for the applications which re-
quire tokenization. Almost all platforms contain the basic fea-
tures of a smart contract system including the immutable pro-
gram code, the decentralized ledger, and the consensus layer.
Figure 1 reflects a few leading smart contract platforms. Table
3 summarizes the main application contexts and related works.
Table 4 includes a relative comparison of the features of each
smart contract platform.
2.1. Ethereum
Ethereum [47] is defined as a distributed computing platform
which is composed of a network of computers operating in a de-
4

Hyperledger
Ethereum
BlockchainSmart Contract
Ethereum Virtual Machine
Gas Web Client
Ether
Gas
Solidity
Ethereum Virtual Machine
Ethereum Account
Orderer
Membership Service Provider
Hyperledger Composer
Clients
Peer
Endorsement
Ordering service
Chaincode
Peer CA
Hyperledger Node
Chaincode Blockchain
NEM
Namespace
Mosaic
Account
Nano Wallet
Apostile
NEM Blockchain Node
Blockchain
API Gateway Server
Application Server
R3 Corda
Flows
States
Contracts
Services
Serialization whitelist
Corda Blockchain Node
Node Explorer
Blockchain
Vault
CorDapps
Stellar
Anchors
Stellar consensus
Lumen
Stellar Blockchain Node
Internet Banking
Blockchain
Stellar Core
Stellar Horizon API
Mobile Wallet
Waves
Tokeneconomica
Waves client
Smart Asset
Waves Blockchain Node
Blockchain
Waves client
Figure 1: Important smart contract platforms
5

Table 3: Smart Contract Platforms and their Applications
Platform Main Application Contexts Related Works
Ethereum •Financial
•Asset trading
•DAI [29]
•Gitcoin [30]
•Cryptokitties [31]
Hyperledger Fabric •Supply chain
•Trade finance
•Stock trading
•IBM Food Trust [32]
•Everledger diamond blockchain [33]
Corda •Energy trading
•Insurance
•Retail markets
•Energy Block Exchange [34]
•TradeCloud[35]
•MonetaGo[36]
NEM •Augmented reality
•Advertising and marketing
•Banking
•Gaming
•Music and entertainment
•DigitCoin[37]
•Bankera[38]
•Pantos[39]
•Verses[40]
Stellar •Remittance •StellarX[41]
•Tempo[42]
•TillBilly[43]
Waves •Customized asset trading
•Ride sharing
•TokenEconomica[44]
•TradiSys[45]
•Multi Chain Ventures[46]
centralized, self-governing and democratic manner. Ethereum
executes smart contracts and deploys decentralized applications
which is called dApp. The front-end can be deployed as web
application with associated backend as a solidity smart con-
tract. Ethereum uses token such as ERC-20 and ERC-721 to
operate with the smart contracts. Ethereum Gas is the unit to
measure the computational overheads in the smart contract ex-
ecution. Gas cost is the monetary value to be spent by the user
for a smart contract execution. Gas limit is the maximum price
which is the blockchain platform user willing to pay for the
smart contract execution.
2.1.1. Advantages
•Open source system: The governing body of Ethereum
does not charge for the source codes. The source codes
available publicly and open for the contribution of devel-
opers around the world.
•A worldwide developer community in contribution:
Huge community of developers contribute to the evolution
of Ethereum. The issues and improvements can be pub-
licly handled with the involvement of different developers
worldwide.
•Availability in private and public mode: The Quorum
is the private mode of Ethereum blockchain. The users
have the capability to decide the operational mode of
blockchain as per their requirements.
•Availability of native cryptocurrency : The native cryp-
tocurrency Ether is available to trade as well as incentivize
the members as per the different requirements.
2.1.2. Disadvantages
•Public ledger storage overheads : The public ledger is
expected to download when a member node required to
connect the network. However, the storage is growing con-
tinuously which incur some overheads in the storage for
the member nodes.
6

•Transaction approval time : The transaction approval
time varies from seconds to minutes which will be not sup-
portive to the realtime requirements of transaction process-
ing. For an instance, the retail payments are hard to accept
using the Ethereum due to the transaction time.
•Transaction cost: The computational overheads of smart
contract execution determined as the gas cost. The gas cost
eventually incur financial overheads to the members in the
network.
•Single programming language support: The program-
ming language of the smart contract limits to Solidity,
which is mostly similar to Javascript. The single program-
ming language restricts the experts of other programming
languages.
•Integration limitations:The integration support of the
Ethereum yet to be further evolved with different appli-
cation contexts such as IoT.
2.2. Hyperledger Fabric
Hyperledger Fabric is a permissioned blockchain platform
which is designed for the enterprise-grade usage. Hyper-
ledger Fabric was adopted to a micro-service based architec-
ture for convenient deployment. The ledger developed on top
of CouchDB no-sql database. The smart contract called Chain-
Code in Hyperledger terminology can develope using Java,
NodeJs and GoLang programming languages. The micro-
services of a Hyperledger blockchain network includes peer,
Certification Authority (CA) , CouchDB, orderer, and chain-
code. Each microservice deployed as a docker container. They
are interconnected using remote procedure calls. Hyperledger
presents an array of specialized versions and utilzation tools
for the blockchain platform. Hyperledger Fabric, Hyperledger
Indy, and Hyperledger Sawtooth are the significant examples.
Each version has developed with specialization in different con-
texts.
2.2.1. Advantages
•Permissioned operational capability: The permissioned
operational capability provides a flexibility of the stake-
holders to select which nodes to be operated, scope of
ledger, and improved privacy. In contrast, the public
blockchain platforms like Ethereum add transactions to the
public ledger to make them publicly accessible which will
raise privacy flaws.
•Different modes of consensus (Solo, RAFT, Kafka):
The Hyperledger provides different consensus mechanism
integration capability which provides the flexibility to
the users. The public blockchain frameworks such as
Ethereum do not support custom consensus mechanisms
as it will require to customize other member nodes.
•No transaction costs: There are no transaction costs
for the Hyperledger blockchain. In contrast with public
blockchain such as Ethereum, the transactions will not
charge from the members as the blockchain will be de-
ployed on the members’ infrastructure.
•Different programming language support (Java, JS,
Go): The Hyperledger provides SDK for a flexible inte-
gration in different applications.
•Microservice adopted architecture: The microservice
architecture provides simplicity and flexibility with the
containerization. The containerization provides conve-
nience in the version controlling and other related opera-
tions. In contrast, the public blockchain networks are hard
to upgrade upon identification of the software issues.
•Rich queries in the ledger: The transaction data stored in
the CouchDB database. The ledger inherits a rich querying
capability from the CouchDB.
2.2.2. Disadvantages
•No native cryptocurrency: There is no native cryptocur-
rency in the Hyperledger blockchain platform. If it is
required, the cryptocurrency should be developed by the
smart contracts.
•Complexity in deployment : The deployement of
blockchain platform is relatively complicated in contrast
to the platforms like Ethereum.
•Number of proven usecases are relatively low: The Hy-
perledger blockchain platform is still evolving by address-
ing different requirements.
2.3. Corda
R3 Corda is a permissioned blockchain platform which can
utilize to deploy legalized contracts with privacy preservation.
The transactions of Corda platform performed in a legally en-
forceable manner. The platform is used in a vast variety of ap-
plications such as financial, healthcare and so on. The flows,
which are the sequences of steps leading to a ledger update de-
fine the execution routing of the smart contract.The state of the
R3 Corda platform represents the smart contract which corre-
sponds to the real world contracts.
2.3.1. Advantages
•Extended privacy prservation: Corda was initially de-
signed to cater the banking industry. The concept of no-
taries was intended to be operated by the banks. In contrast
with the Ethereum, the notaries are the miners who verify
the transactions.
•A broad industrial compatibility: Corda supports for
different industrial applications with capability to enforce
ordinary contracts as smart contracts.
•Regulatory and supervisory node support: Corda sup-
ports regulatory and supervisory nodes to align with the
existing banking ecosystems.
7

•Realistic contractual enforcement capability: The corda
is convenient for the enforcement of business logic as the
smart contract. The platforms
•Different consensus mechanism support: Corda sup-
ports pluggable consensus mechanisms to enhance the
flexibility of operations. The consensus mechanism of
Corda is twofold, as transaction validity consensus and
transaction uniquness consensus.
2.3.2. Disadvantages
•No native cryptocurrency: There is no native cryptocur-
rency included in Corda.
•Verification only through trusted notaries: The trusted
notary service aligns the Corda system with the finan-
cial services requirements. It can be argued that notaries
may drive the system towards trusted third party features,
which is expected to be eliminated in blockchain principle.
2.4. NEM
The NEM is a blockchain-based cryptocurrency platform
which is associated with significant value-added features. NEM
has the extra capabilities such as identity proof, timestamping
documents, and creation of customized digital assets. The NEM
has strong potential to use in industrial applications when com-
paring with other cryptocurrencies. There are many potential
usecases with NEM beyond peer-to-peer value transfer.
2.4.1. Advantages
•Built in cryptocurrency: The NEM has its own cryp-
tocurrency XEM which can be used as an asset, like
Ethereum.
•High transaction throughput: The transaction through-
put of NEM is relatively higher than Ethereum and Hyper-
ledger.
•Improved Proof of Importance consensus algorithm:
The consensus algorithm Proof of Importance is encour-
aging the participants buy cryptocoins and remain active
fort the contribution.
•Delegated harvesting usage: Delegated harvesting en-
ables more members to contribute for the functioning of
network
2.4.2. Disadvantages
•Limitations of the documentation: The documentation
and other materials for the NEM blockchain are relatively
low when compared with Hyperledger and Ethereum.
•Comparably less number of tools available: The num-
ber of tools for the NEM blockchain is relatively low
when compared with the other platforms like Hyperledger
Fabric. The Hyperledger platform provides a vast array
of tools such as Hyperledger composer to easily created
blockchain solutions.
•Lacking of community contribution:The developer
community of the NEM is relatively low when comparing
with the leading platforms like Ethereum and Hyperledger.
2.5. Stellar
Stellar is a blockchain platform that enables financial trans-
actions beyond frontiers. The Stellar platform provides faster
transaction processing time compared with other cryptocur-
rency platforms. The native cryptocurrency of Stellar is called
Lumen. The transaction processing time in association with
the concept called Anchors is always less than 5 seconds. The
invention utilized the Stellar consensus based on the Ripple
consensus algorithm. Even though the smart contract program-
ming language is not Turing complete, the smart contracts can
be used to multi-signature transactions and future executions.
Turing completeness limitation was explicitly imposed in order
to mitigate the security risks of Turing complete programming
languages.
2.5.1. Advantages
•Cryptocurrency support : Stellar has its own cryptocur-
rency called Lumen which supports the different opera-
tions
•Pre-generated cryptocurrency : Stellar Lumens are pre-
generated. Hence, there is no computataional overhead for
mining, such as Bitcoin which will be more beneficial for
the users
•Faster transaction processing time: The transaction
confirmation time is 3-5 seconds, which makes it easy to
integrate for retail payments
•Enhanced security through non-Turing complete
smart contract language : The capabilities of the non-
Turing complete smart contracts are limited.
2.5.2. Disadvantages
•Integration issues with the existing banking systems:
The Stellar originally intended to use for the financial
transactions. There are difficulties with the integration of
blockchain with the existing systems such as SWIFT.
•Regulatory difficulties with the legal frameworks:
Since the blockchain is still not evolved technology, there
are some regulatory limitations as most of the legal sys-
tems do not define blockchain based transactions.
2.6. Waves
The Waves smart contract platform is a Scala programming
language based open-source blockchain platform. It allows
users to launch their own cryptocurrency token and facilitates
with Decentralized EXchange (DEX). They have introduced the
concept of custom application tokens, which is tailor-made for
the user requirement. The platform enables users to create, is-
sue, transfer assets, and exchange custom tokens within 5 min-
utes. The smart contract language used in Waves platform is a
non-Turing complete language.
8

Table 4: Smart contract platforms relative comparison
Features Ethereum Hyperledger
Fabric
Corda NEM Stellar Waves
Operation mode Public Private Private Public Public Public
Smart contract program-
ming language
Javascript Javascript
Java/Go
Cotlin/Java Custom Custom Custom
Consensus mechanism PoW Pluggable Raft Proof of Im-
portance
Stellar con-
sensus
Leased PoS
Latency (Confirmation
time)[48], [49], [50], [51]
15min 1 second Not pub-
lished
1-2 min 1-5seconds 10 min
Throughput [52], [53],
[54], [55], [56]
20tps 20,000 tps 15-1,678 tps 4,000 tps 1,000 tps 500 tps
Native cryptocurrency Ether None Corda coin XEM Lumens Waves
Smart contract Turing
completeness
Turing com-
plete
Turing com-
plete
Turing com-
plete
Turing
incomplete
Turing
incomplete
Turing in-
complete
and basic
functional
smart con-
tracts
Transaction privacy [57],
[58]
No privacy
on public
ledger
Privacy
through
channels
Privacy
through
techniques
such as
partial data
visibility
No privacy
on public
ledgers
No privacy
techniques
Provides
confidential
data transfer
and storage
2.6.1. Advantages
•Custom token creation capablity: The capability to cre-
ate custom wallets simplify the tokenization market to
the new entrants. In contrast with the platforms such as
Ethereum, the custom token creation is a distinguishing
benefit of Waves.
•Non-Turing complete language for better security : The
Non-Turing complete smart contract language limits the
risk of utilization of smart contracts for attacks.
2.6.2. Disadvantages
•Exposed to volatility in the monetary system through
custom tokens: The concept of custom tokens may create
an artificial volatilty in the market.
3. Applications of Smart Contracts
The key application areas and the role of smart contracts are
presented in this section. Figure 2 illustrates a quick overview
of different smart contract based applications.
3.1. Financial Applications
The self-executory, immutable, and distributed nature of the
smart contracts revamp the financial industry in a few dimen-
sions by solving many existing issues. Smart contracts guaran-
tee the defined operation to be executed on a certain state of the
system and it will be executed without any error. The competi-
tive advantages of the blockchain-based smart contracts for the
financial companies are highlighted in [59]. Figure 3 reflects
these benefits of the smart contracts in the financial applica-
tions. Moreover, Table 5 summarizes the key challenges related
to each financial applications and benefits of smart contracts to
resolve them.
3.1.1. Currency management
Currency is one of the most important elements in the finan-
cial industry. Currencies which are declared by a legal tender
and controlled by a national central bank are called Fiat curren-
cies. United State Dollars and Euro are well-known examples.
Usage of Fiat currencies incurs the stakeholders a lot of over-
heads such as storage and transportation with high level of se-
curity. In the consumer’s perspective, the centralized link with
the central bank in fiat currency exposes the financial strength
of each individual to the government. The government or bank
can reverse a committed transaction without consumer’s con-
sent too. In addition to that, identity theft has become a major
9

- Cur rency
- K now Your Customer
- Escrow
- Insurance
- Lending
- Audi tng
- Stock Trading
Currency
- H ealth Information M anagement
- Cl inicial Research D ata Protection
- Automated Patient Moni toring and Treatment
Healthcare
- Identit y Data Protection
- D ecentrali zed I dentit y Management
- D ecentrali zed A ccess Control
Identity M anagement
and Access Control
- Improved Secure T ransaction Process
- Eliminated Processing Fees and Commi sions
Real Estate
- Smart Contracts for Scalable Resource Sharing in IoT
- Smart Contracts in Edge C omputing
- Smart Contracts for the Enforcement of IoT Securit y
- UA V
- Smart Cities
Internet of Things
- Smart Contracts for Automated R esource Sharing in IoT
- Tenant Identity Management and Access Control
- Enforcement of Roaming Security
Telecommunication
- Ensur ing Sea/Air Freight Supply Chain Tracability and Compliance
- Speci al Commodit y Supply Chain Tracability
- Agricultural Supply Chai n Provenance and Tracabilit y
Logistics
- Enforcement of Law by Smart Contracts
- Smart C ontracts to Automate Contractual Agreements
- Smart C ontracts for Public Services
eGovernment/ Law
- Energy Trading
- Waste Management
- Automoti ve Industry
- Additive Manufacturing
Cross Industry
Blockchain and Smart
Contracts
Figure 2: Different smart contract applications
Currency
- Eliminates intermediary
- Near real-time transfers
- Enablescurrency beyond frontiers
- Improved security
Smart Contracts in Financial Applications
Know Your Customer
- Provides a global platform for all banks
- Customers can control the access of their own data
- Data alterations can be tracked by the data owners
- Can eliminate single point of failure
Insurance
- Eliminates frauds
- Automated insurance claims
- Can establish transparent insurance policies
Lending
- Eliminatesf rauds
- Automated settlements
- Automated interest calculation
Auditing
- Transaction transparency is guaranteed
- Guaranteed accuracy of audit reports
- Cost savings of manual auditing
Stock Trading
- Eliminates charges
- Improved security
- Realtime settlement
Figure 3: Benefits of Smart Contracts in Financial Applications
issue in today’s financial world with Fiat currencies. The finan-
cial account information stored in the centralized systems in all
leading payment organizations. The identity information such
as Card Verification Value (CVV) of credit cards are vulnerable
to domain expert hackers. The international remittance in Fiat
currency is mostly not real-time and subject to commissions by
the intervening banks.
Cryptocurrency is a revolutionary innovation of recent years
to address most of these aforesaid issues. Powered by the
blockchain technology, cryptocurrency is a digital asset secured
with cryptographic techniques and operable with the smart con-
tracts. Since the cryptocurrency is a “digital” asset, robust phys-
ical security is not required as the Fiat currency. Cryptocur-
rency transactions considered as psuedo-anonymous, since the
complete identity of the sender and receiver not revealed by
a third party, in contrast with the transactions routed through
banks. Once committed, the transaction be recorded on a block
and distributed among all the nodes in the blockchain ensures
that any party cannot reverse the transaction as centralized
banking transactions. The cryptocurrency transactions cannot
be replayed when comparing with the credit card transactions.
Bitcoin by Satoshi Nakamoto is the first successful cryp-
tocurrency in the world [1]. Eventhough Bitcoin does not di-
10

rectly support smart contracts, there are several approaches fol-
lowed by researchers to incorporate smart contracts, such as
[60] and [61]. Ethereum [47] is another prominent cryptocur-
rency innovation. Ethereum is not only a platform which pro-
vides a virtual computing environment called Ethereum Virtual
Machine (EVM), but also Turing complete programming lan-
guage to write smart contracts to run on the blockchain. In
currency perspective, Ethereum declares its native token called
“Ether” which is a bearable digital asset.
Hu et. al[62, 63] proposed Ethereum based payment solution
for rural areas with non-persistent internet connectivity. The
transactions were handled by the nodes connected to a local
base station and transactions were processed by the miners and
periodically connects to the synchronization of balances. Bowe
et al. presented ZCash [64], which is an anonymous decen-
tralized payment scheme that allows private transactions on a
public blockchain using cryptocurrency. Duffield et al. [65] il-
lustrated Dash which is a privacy-centric cryptocurrency based
on Bitcoin. There are significant improvements in Dash when
compared with Bitcoin, such as a two-tier incentivized net-
work and which enables private transactions and instant trans-
fers. Rosner et al.[66] identified Ripple as a seamless payment
scheme that enables cross-border transactions seamlessly. The
authors pointed out the significance of regulatory authorities to
regulate the transactions committed on decentralized payment
systems.
3.1.2. Know Your Customer
Anonymous customers are restricted in almost all banks in
the world to prevent money laundering and other illegal activi-
ties. Preliminary information such as names, addresses, social
security numbers and contact numbers recorded by the banks
after a formal customer screening process. If spurious activities
are committed by the customers, those activities can trace and
map along with their identities for further investigations. Ev-
ery bank adhered to their own specification of Know Your Cus-
tomer (KYC) process. This process includes a lot of paperwork
and usually does not have a standardize way for cross-bank ver-
ification of an individual. The people conceal their identities
in money laundering activities due to non-standardization and
most of the times banks will be penalized for such criminal ac-
tivities. In addition to that, the customers do not have authority
to control the ownership of data.
In this regards, the incorporation of smart contracts can
emancipate most of the awkward manual operations while en-
hancing the privacy preservation. Data alterations are traceable
by both the bank and customers through the distributed ledger.
Customers will have the ownership of data and can control the
access to data to eliminate misuse of data. Anyone who need
to access the data, has to request permission from the customer.
Smart contracts can be used to enable such access dynamically.
In addition, the distributed data storage enhances the single
point of failure and risk of data loss as well. The blockchain
based data storage ensures the availability of the service with
its distributed service architecture.
Ye and Liang[67] discussed the benefits and how the smart
contract transformation will revolutionize the banking indus-
try. The author suggested that all data should store in the fi-
nancial institutions in encrypted form and a summarized ver-
sion of data should be shared to the public ledger. Moyano
and Ross [68] proposed a Ethereum based KYC system to re-
duce the operational cost and enhance the customer experience.
The authors also discussed the capability to incorporate per-
missioned blockchain such as Corda for the system. Alex et
al.[69] proposed privacy preserving KYC scheme on Ethereum,
which leverages the customer onboarding with compliance to
the regulatory requirements. The system defined two smart con-
tracts naming KycProvider and KyceToken. Each smart con-
tract maintains access related information and functioning as
standard ECR - 20 token for the KYC checks.
3.1.3. Escrow service
Escrow is an essential service in the online international trad-
ing marketplaces. Escrow is a widely used technique to ex-
change funds in the international transactions. It acts as the
trusted mediator in classical international trade ecosystems.
Since there is no face-to-face meetings and physical contract
establishment in the online international transactions, a trusted
intermediary is a mandatory service. Escrow services require
a service charge which a certain percentage of the transaction
value. The present escrow services have non-realtime settle-
ment processes with non-standardized dispute resolution mech-
anisms.
This requirement of a trusted third party in the escrow service
is fueling the use of autonomous platforms such as blockchain
based smart contracts. Application of the smart contract elim-
inates the transaction delays. The smart contracts enable near
real-time settlements and the embedded rules will charge the
penalties for delayed payments and delivery. The distributed
service architecture of the smart contract will eliminate the sin-
gle point of failure and ensure the service availability to stream-
line the business.
Peters [70] discussed the blockchain technology, smart con-
tracts and its application in the global money remittance. The
author discussed the possibility of multi-signature escrow ser-
vices with smart contracts. The author also highlighted the key
requirement of the smart contracts anticipated in the escrow in-
cluding accuracy and trust. Bogner et al. [71] demonstrated a
decentralized Ethereum based application for sharing tangible
objects in everyday use. The solution implemented associating
a web application and a mobile application that is capable of
reading a QR code displayed on the objects. The system uti-
lizes an escrow service to hold the associated fees as per the
requirement.
3.1.4. Insurance
Insurance is an essential service to the people for centuries.
People insured numerous assets such as properties, vehicles,
businesses and their own lives. Any insurance agreement com-
posed of an insurer, organization which provides the insurance
and the policy which are often formed as paper contracts have a
longer process in agreements. In addition to that, the insurance
frauds are accountable as more than 40 billion dollars a year, ac-
cording to Federal Bureau of Investigations (FBI) statistics[72].
11

The claiming and settlement process takes time which is unfair
customer experience.
The use of smart contracts in the insurance industry will be
beneficial in multiple dimensions. The smart contract can be
utilized to establish insurance policy terms and conditions in
an immutable manner. No human intervention is required to
settle a claim. Smart contract based auditing and verification
process will be straightforward than the manual process with
the globally distributed public and immutable ledger.
Hans et al. [73] emphasizes the usefulness of blockchain
based smart contracts in the insurance industry. Authors stated
that smart contacts can speeds up the claim processing and
eliminate the administrative costs. The authors also highlighted
that still there are some aspects including scalability, flexibil-
ity, and permissioned operation to be improved before integrate
the smart contract into the insurance industry. B3i [74] is one of
the most significant innovations to the insurance industry in col-
laboration with fifteen giants in the sector. The smart contract
based systems improve the insure and re-insure value chain as
well as improve customer experience in KYC process.In [75],
authours illustrated the possible improvements in the insurance
industry by using blockchain based smart contracts. The au-
thors highlighted the enhanced customer satisfaction through
unified KYC process, fraud detection since each claim trans-
action requires to verify by the number of parties to being ap-
proved, automation of claim processing, and innovative product
integration capability such as micro insurance.
Guo et al. [76] proposed WISChain, which was intended for
web identity security. They provide two insurance service mod-
els for web identity security and commercial website security,
which enables the claim evidences to be uploaded automati-
cally to the blockchain. [77] illustrated a convenient crop insur-
ance for farmers in Ghana. The smart contracts have been de-
fined to compensate the policyholders due to certain conditions
such as drought or rainfall utilizing high resolution satellite im-
ages to identify the weather conditions to eliminate fraudulent
claims. [78] illustrated Etherisc, which is a decentralized and
smart contract based insurance system which defines two types
of tokens for economic incentivization and to represent risks
respectively. It was utilized Ethereum smart contracts to es-
tablish a standardized set of rules to define how stakeholders
should function in the system. Vo et al. [79] presented a per-
missioned blockchain-based solution for the data provenance in
car insurance. The system was implemented using the Hyper-
ledger Fabric platform. The smart contracts were invoked in
capturing events such as weather events, location variations of
the car, and so on.
3.1.5. Lending and borrowing
Lending, borrowing and loans are significant economic ac-
tivities of a civilized nation which are important in the eco-
nomic development. The economic development made the hu-
man needs sophisticated. The lending methods also diversified
among different avenues as per the human needs. Peer to peer
lending was a famous mode since the ancient economic ecosys-
tems. This was transformed into flexible syndicated products
presented by major financial institutions. Here, banks act as
trusted third parties. Banks are the only authorized reposi-
tory of money for lending and dominate the lending market.
The current mortgage and loan processing often spans about 60
days[80]. This arduous process includes ascertaining loan ap-
plicants’ credit scoring, and underwriters’ profile verification.
12

Application Key challenges
Blockchain features
Key benefits
Decentralization
Forge resistance
Transparency
Autonomous execution
Accuracy
Know Your
Customer: [67],
[68], [69]
•Improved customer
experience
•Cross bank verification
capability for customer
details
•Data alteration can be
tracked through ledger
•Universal data sharing is
possible
•Eliminated overheads
•Better customer
experience
•Access to the data can be
controlled by the data owner
Redundant data entry at all
banks
X
Administrative overheads X X X
Cumbersome customer ex-
perience
X X
Data security and user pri-
vacy issues
X
Data alteration cannot be
tracked
X X
Data duplication overheads X
Universal data sharing is im-
possible
XXX
User cannot control access
to his data
X
Escrow service:
[70], [71]
•Transparency
•Non repudiation
•Settlement is faster
Settlement delays X X
Expensive service fees X
Non repudiation is hard XXX
Insurance: [73],
[74], [75], [76], [77],
[78], [79]
•Immutable policies
•Transparent policies
•Reduced overheads
•Fraudulent claims
eliminated
Insurance policies and terms
and conditions are men-
tioned as paper contracts
X X X
Auditing and verification of
claim is a separate process
X X X X
Fraudulent claims X X X X
Claiming process is costly X X
Lending: [81], [82],
[83], [84]
•Immutable policies
•Automated recovery
process
•Reduced overheads
•Transparent credit scoring
•Transparent agreements
Time and cost intensive ver-
ification processes
X X
Credit scoring is a manual
and non-transparent process
X X X X
Administrative costs X X X
Auditing:[85], [86]
•Improved accuracy
•Automated audit process
•Elimination of specialized
human intervention
Time and cost intensive ver-
ification processes
XXX
Credit scoring is a manual
and non-transparent process
XXX
Administrative costs X X
Stock Trading: [87],
[88], [89], [90], [91]
•Transaction transparency
•Decentralization and
ensured availability
•Improved accuracy
Centralization X
Transactions will be charged
by centralized authorities
X X
Transparency is not avail-
able
X
Table 5: Summary of Applications of Smart Contracts in Financial Context
13

In addition to that, the loans were subject to processing fees
and few other surcharges imposed by the bank. Some hidden
charges can surprise the customers too. Borrowers sometimes
escape and refuse to pay back the loan.
The smart contracts circumvent the existing issues and
promise a trust based ecosystem which streamlines the appli-
cation and payment with automatic execution. The smart con-
tracts can automate the different manual processes which hinder
the loan processing, utilizing the distributed ledger. Credit scor-
ing, expense history analysis are few possible solutions which
can be ideally replaced with the smart contracts to improve the
process. Salt Lending [81] is world’s one of the largest lend-
ing platforms with market capital of USD 126 millions. The
borrowers send collateral to Salt’s multi signature wallet in ac-
cording to enforced conditions automatically. EthLend [82] is
an Ethereum based lending platform. The important attributes
such as loan terms, fund transferring conditions, and collateral
are being handled by smart contracts with ERC-20 tokens. Ev-
erex [83] is a Singapore based lending and remittance service.
Everex provides a transparent platform for the unbanked cus-
tomers in South East Asian countries. It uses ERC-20 token
which can be pegged with fiat currencies. Debitium [84] is one
of the Ethereum based crowdfunding platforms. It facilitates
cross border deals and connects borrowers and investors.
3.1.6. Auditing procedures
The Auditing is a significant activity in an organization. Due
to regulatory requirements, the organizations have to undertake
the audit through a trusted independent third party organiza-
tions. These organizations charge explicitly for their opera-
tions. The audit operation is a tedious manual process which
requires substantial human intervention. The derived insights
from the audits will depend on human accuracy.
Audit procedures associated with smart contracts automate
the audit procedures and eliminate the additional costs and hu-
man errors. The accuracy is guaranteed by the autonomous ex-
ecution of smart contracts in real-time. Due to the distributed
and transparent nature of the smart contract, the regulatory au-
thorities can trust the executory conditions are not being tam-
pered. Also the smart contracts can customize to derive deeper
insights for data analytics.
Zou et al. [85] proposed a blockchain based audit scheme
to eliminate forging of audit records. Rozairo et. al. [86] ex-
plained the applicability of smart contracts in the auditing pro-
cedures. Still the auditing require some more contribution of
the blockchain based solutions.
3.1.7. Stock trading service
Stock exchange is one of the most prominent activity in a fi-
nancial structure. Most of the countries trade stocks valued in
millions of dollars per day within traders. These traders are
ranging from individual investors to multi millionaire public
listed companies. Each transaction executes by intervention of
different parties including brokers of the buyer and the seller,
clearing houses and transferring agents. The current setup im-
poses commissions and charges on each player and prone to hu-
man errors. Sometimes the settlement is not realtime. Further-
more, the fiat currency based architecture operates with cen-
tralized governance architecture which limits the market access
restricted to the people. The stock trading market access con-
trolled through the registered brokers, which introduced addi-
tional overheads of time and cost to the people who are inter-
ested in trading.
The centralized trading architecture can be eliminated by in-
corporating smart contracts and will enable peer to peer transac-
tion capability for the traders. The terms and conditions can be
established transparently by using smart contracts. There is no
centralization of trust is required since the ledger is decentral-
ized and the network guarantees the conditions are immutable
over the network. Therefore, smart contracts will empower the
next generation stock exchanges eliminating human errors, cen-
tralization and additional charges incurred on traders along with
faster settlement.
Yermack [87] discussed the advantages of blockchain based
smart contracts for corporate governance and how financial as-
set trading will be benefited from smart contracts. The au-
thor emphasized that the improvement of tracking the owner-
ship with public ledger will be accurate in financial record-
keeping with greater transparency as well as improve the liquid-
ity. The author elaborated that countries including the USA and
Australia started experimenting with smart contract powered
security trading platforms. [88] presented TITA which is an
Ethereum blockchain based system which supports commodity
trading for manufacturers and consumers. The system defines
a token to enable purchases and transfers and incentivizes the
token generating contributors of the network. Smart contracts
transfer assets or establish escrow conditions as required. [89]
is a prominent application of permissioned blockchain based
smart contract application for stock exchange in Australia. It
provides automated clearing and settlement by smart contracts
along with some significant post-trade activities. They provided
Digital Asset Modeling Language (DAML) and run privately
on a defined set of nodes.[90] and [91] in Hong Kong developed
by following the Australian Stock Exchange implementation.
3.2. Health Care Related Services
The research and development in the health care domain have
increased the life expectancy. As a result, the number of el-
derly people in the world who will require periodical medical
attention is gradually increasing. New insurance schemes such
as Affordable Care Act enrollment in the USA increased the
number of patients seeking preventive medicine who were pre-
viously reluctant on medical care due to financial constraints.
These reasons increased the volume of patients significantly
over the the past few decades. Handling such an unprece-
dented volume of patient data manually is a cumbersome pro-
cess. Manual processes incur significant administrative over-
heads and prone to life critical human errors. The digital trans-
formation will eliminate these issues associated with the man-
ual process but exposed to an array of data security threats. If
these information systems integrated with prescription drug op-
erations, the complexity and security requirement of the ecosys-
tem will be increased drastically.
14

Health Information Management
- Secured health information storage
- Safer access control to patient data
- Regulatory compliance requirements
- Improved privacy protection
Smart Contracts in Healthcare Applications
Clinical Research Data Protection
- Access control for the life criticl clinical research
data
- Ensuring data integrity
- Regulatory requirements
- Ensured availability
Automated Patient Monitoring
and Treatment
- Automated access control
- Life critical accuracy in treatments
- Complianceand regulatory requirements
- Improved reliability
Figure 4: Smart Contract Applications in Healthcare
Therefore, incorporation of the smart contracts to the health
care ecosystem will be significantly effective in different di-
mensions. A quick overview of smart contract applications
on healthcare displayed on Figure 4. Table 6 summarizes the
applications of smart contracts in the healthcare context along
with the benefits and challenges. Candereli et. al [92] explored
the opportunities in healthcare with a scientometrics analysis.
McGhin et al. [93] presented a comprehensive review on re-
search challenges and opportunities in the blockchain in the
healthcare context.
3.2.1. Health information management
Modern medical institutions are mostly empowered with au-
tomation techniques to handle the myriad volume of patients.
The IoT integration is a wider domain including remote treat-
ments and real-time monitoring. These systems generate a mas-
sive amount of patient data which is confidential and life crit-
ical. But most of the systems in some countries are not com-
pliant with international standards such as the Health Insurance
Portability and Privacy Act (HIPAA). Some systems are still
rigid and still may require some paperwork. The health infor-
mation system must ensure data privacy and integrity, as well
as availability. These services are indispensable in the health
context rather than the other industries because the medical
information is highly relevant in invaluable life assets. The
blockchain technology and smart contracts can be applied to
enable the health information management systems to ensure
privacy, integrity and access control to achieve regulatory com-
pliance along with the enhanced patient experience.
Azaria et al. presented MedRec [94] , a decentralized elec-
tronic health record management system which enables the pa-
tients to access their medical records across multiple treatment
sites. The system is being leveraged by the blockchain and
smart contracts, developed on Ethereum platform and manages
authentication, confidentiality, accountability and data sharing
with a crucial consideration on sensitive patient information.
The system is interoperable with existing medical record eco-
systems. Nichol and Brandt [95] presents a concept for co-
creation of trust in healthcare, using three conceptualized pos-
tulations as interoperability, security, and payment. The authors
explained with examples clearly how the blockchain based
smart contracts will solve different problems in healthcare in-
cluding the trust establishment and frauds. The authors defined
blockchain based smart contracts will be a game changer in fu-
ture of healthcare.
Kuo and Lucila [96] presents Modelchain, an adaptation of
blockchain based smart contracts for the privacy preserving
healthcare predictive modeling framework. The authors de-
signed a framework to integrate online machine learning with
blockchains and utilized transaction metadata for the predic-
tive model dissemination. The authors designed a new proof-
of-information algorithm on top of proof-of-work conesus al-
gorithm to determine the order of online machine learning on
blockchain. Dagher et al. [97] proposed Ancile, which enables
secure, interoperable, and an efficient access control framework
to medical records by the patients along with privacy preser-
vation using Ethereum smart contracts. The solution transfers
the ownership and control of the patient himself. The sys-
tem developed with six smart contracts for operations includ-
ing consensus, classification, ownership of data, permissions
and re-encryption and maintains hashes of the records for in-
tegrity. The system enables data ownership transfer permission
to the patient and compliant with HIPAA requirements. Yue et
al. [98] proposed Healthcare Data Gateway (HDG), which is a
blockchain powered mobile application allows patients to con-
trol the access of medical data by his own to ensure patient data
privacy. The authors portrayed the application of Secure Multi-
Party Computation on patient data to enable untrusted parties to
compute patient data within privacy limits defined. The system
used blockchain storage platform to manage data by the patient
and the authors discussed about new hopes on 5G to faster data
manipulation with enhanced network speed.
Novikov et al. [99] presents a blockchain based smart con-
tract based distributed data register for creation of electronic
medical card and an algorithm for the use of smart contracts.
The authors have highlighted the establishment of reliability
and transparency through blockchain and its significance on the
medical information system. The authors suggested Ethereum
platform for development of the suggested Integrated Elec-
tronic Medical Record register. Alexaki et al. [100] presented a
conceptual medical record access and sharing mechanism pow-
ered by blockchain based smart contracts. The authors sug-
gested development of the system based on either Ethereum
or Quorum, which is the permissioned version of Ethereum
blockchain. The authors applied smart contracts for significant
roles including identity registration, patient record management
and electronic patient record access agreement. Kuo et. al
[101] presented an open discussion on the benefits, pitfalls and
latest applications of blockchain based smart contracts to the
biomedical and healthcare domain. The authors discussed the
key benefits including improved medical record management,
enhanced interfacing with insurance systems for the claim-
ing process, accelerated clinical and biomedical research and
data transparency and enhanced medical ledger with robust-
ness and security. The authors discussed the key challenges of
blockchain in healthcare is the publicly available health records.
15

Application Key challenges
Blockchain features
Key benefits
Decentralization
Forge resistance
Transparency
Autonomous execution
Accuracy
Health Information
Management: [94],
[95], [96], [97] ,
[98], [99], [100],
[101]
•Accuracy of life critical
operations
•Robust access control to
the systems
•Data alteration trackable
Attacks will affect the hu-
man lives
X X X
Human oriented program-
ming errors
X X X
Access control issues to the
control systems
X X X
Clinical Research
Data Protection:
[102], [103],
•Privacy enforcement
•Eliminated centralization
•Ensured availability
Integrity requirements X X X X
Compliance requirements X X X
Access control requirements X X X
Automated Patient
Monitoring and
Treatment:[104]
•Accuracy of life critical
operations
•Robust access control to
the systems
•Ensured integrity of
accumulated data
Attacks will affect the hu-
man lives
X X X
Robust access control to the
systems
X X X
Ensured integrity of accu-
mulated data
X
Table 6: Summary of Applications of Smart Contracts in Healthcare Context
16

3.2.2. Clinical research data protection
The data integrity of clinical trials is a major concern in
medicine. The data integrity defined as the extent which the
electronic and paper based data are complete, consistent, ac-
curate, trustworthy, and reliable throughout the data lifecycle.
There are guidelines such as International council for harmo-
nization guideline for good clinical practice established to reg-
ulate the data integrity in different perspectives. The significant
problems of the credibility of scientific data are data loss, end-
point switching, data dredging and selective publication. The
treatments due to distorted data will expose the patients into a
life risk. The paper based systems do not guarantee the integrity
of data. The risk exists of losing the printed or hand-written pa-
pers where the data rests. Eventhough the computer systems
utilized, still some robust security measures should be applied
to prevent data loss and theft. Sometimes, the digital form of
data will be more vulnerable than paper written data. The clin-
ical research data repositories associated with smart contracts
will be the ideal solution to enforce access control and regula-
tory compliance.
Nugent et al. [102] signified the enforcement of regulatory
requirements and trust in clinical research data by blockchain
based smart contracts using Ethereum platform. The smart
contracts, naming as regulator contract and the trial contracts
acted as trusted administrators of the system. The authors
utilized two smart contracts. The regulator contract holds a
data structure for clinical trial authorization while the trial con-
tract is built using functions within the authorization contract.
Zhang et al. [103] proposed a framework on managing and
sharing electronic medical records of cancer patient care using
Hyperledger Fabric blockchain platform along with symmet-
ric and asymmetric encryption techniques as well as proxy re-
encryption. The authors proposed that privacy, security, avail-
ability, and fine-grained access control over medical data en-
sured and mainly focused on the secured sharing of medical
data, for research or treatment requirements between medical
organizations. The smart contracts eliminated the requirement
of trusted third party and ensures privacy and access control
policy defined by the patient and used encryption techniques to
store the data on the ledger. When comparing [103] with [102]
, there are significant differences can be identified. [102] was
built on Ethereum smart contract, which is a public blockchain.
The public blockchain transactions are cost intensive with ac-
count management and mining contribution. In contrast, [103]
implemented on Hyperledger Fabric private blockchain which
provides flexibility for the stakeholders to regulate. For an in-
stance, Hyperledger Fabric enables the nodes to define consen-
sus policy according to their preference.
3.2.3. Automated patient monitoring and treatment
The IoT and wearable devices have been embraced by peo-
ple from smartwatch to Wireless Body Area Network (WBAN).
The WBAN leverages IEEE 802.15.6 and IEEE 802.15.4j
standards which were specifically standardized for medical
WBANs. The core objective of WBAN is to improve the com-
munication speed, accuracy, and reliability of sensors attached
in the immediate proximity to the human body. The WBAN
sensors may generate a massive amount of data such as blood
glucose level, the pulse rate, blood pressure, and so on. The
expansion of such systems raised the requirement of privacy,
access control and integrity of data. Each device should be
operated with robust automated access control mechanism to
eliminate the risk of the patient. Rogue access to the auto-
mated patient monitoring and treatment system can kill the pa-
tient within few seconds by jamming the treatments. The smart
contracts will be the next generation solution to eliminate the
risks by controlling access and autonomous safe execution of
the treatments in automated patient monitoring and treatment
systems.
Griggs et al. [104] proposed a system which utilizes private
Ethereum blockchain and master-slave modeled medical device
deployment model. The sensors connected with the smart de-
vice, such as either a smartphone or tablet. The sensors can con-
nect to apparatus such as insulin actuators and blood pressure
monitors to execute smart contracts and eventually the records
will transfer to the immutable ledger. The data received by
the smart device is sent to the smart contract, along with the
customized threshold values and smart contracts evaluate the
data and trigger alerts to the patient, healthcare provider and
instructs to the actuator nodes for automated treatment if re-
quired.
3.3. Identity management and access control
Identity management and access control are essential ser-
vices in every enterprise. The classical identity management
systems are mostly centralized and associated with expensive
hardware such as smart cards and hardware security modules.
Centralised systems will elevate the risk single point of failure
and require a robust backup, recovery and disaster management
procedures. There are scalability limitations exist in the central-
ized systems. Sometimes the latency in identity management
and access control can be observed when they were connected
to IoT devices due to computational power limitations.
The distributed ledger technologies will be the next genera-
tion of identity management and access control systems. Smart
contracts based access control systems promise accuracy, high
availability, and fault tolerance. Table 7 summarizes the ap-
plications of smart contracts in the identity management and
access control context along with the benefits and challenges.
3.3.1. Identity Data Protection
The value of personal identity information is proliferating
with the association of modern technologies to the human life.
The devices such as smartphones, wearables generate enormous
amount of personal data such as location, identity informa-
tion and so on. Most of the leading applications, including
social media used by the people are centralized and the user
has minimal rights to control the data. Still most of the users
are unaware of the significance of their personal information.
The incidents like Cambridge Analytica Scandal reflect that
the capability to abuse the personal data without the owners’
consent[105]. Data owners should be capable of controlling the
access of their data to avoid such incidents.
17

The smart contracts are a blessing solution for the access con-
trol of identity information and eliminate data theft. The de-
centralized nature of smart contracts will enable the data own-
ers to control the access of their own data with decentralized
and transparent nature. The distributed ledger is applicable to
record the access of the individual personal data, which ensures
that the data did not access unnecessarily, such as for a third
party.
Banerjee et al. [106] proposed a novel framework associated
with blockchain based smart contracts for users to track how
is their personal identity information is stored, used and shared
by the service provider. The authors developed an automated
access control and audit mechanism which enforces users’ data
privacy when sharing data across third parties. The authors also
mentioned that their system can be adopted by big data users
to automatically apply their privacy policy on the data flow and
track operations. Ouaddah et al. [107] present a blockchain
based privacy preserving authorization management framework
which enables users to control their own data. The authors im-
plemented the initial implementation on the typical IoT use case
on Raspberry Pi. There are few types of transactions used to
grant, get, delegate, and revoke access.
3.3.2. Decentralized identity management
Classical identity management and access control sys-
tems such as LDAP (Lightweight Directory Access Protocol),
IAM(Identity and Access Management) and PKI(Public Key
Infrastructure) are aligned with common centralized architec-
ture. The centralized identity management systems devel-
oped with privileged access management to the administrator(s)
which enable the administrators to manipulate data, central
point of failure and expensive perimeter security requirements
for compliance. The access credentials associated with private
keys will be vulnerable if they are stored in a centralized server,
probably in the cloud. Perimeter security requirements will in-
cur costs to the organizations to deploy expensive Hardware
Security Modules and tokens with extensive administration and
maintenance overheads. If a rogue user disables the centralized
service, entire system will be affected.
Instead of the centralized access control systems, the decen-
tralized system will heal many pains of centralized access con-
trol. The smart contracts will provide access to the individ-
ual user without invocation of centralized service and in net-
work efficiency perspective, optimal than the centralized sys-
tems. The smart contract logic will be transparently deployed
and the users can guarantee that their access control or identity
information not manipulated by a privileged access manage-
ment personal. The distributed nature will ensure the service
is up and running and cannot be halted by attacking a single
server.
Zhang et al. [108] investigated critical access control issues
in IoT and proposed a smart contract based access control sys-
tem with multiple access control contracts. The authors defined
three contract types, as the access control contract, judge con-
tract and register contract. The authors demonstrated the frame-
work using IoT system and a desktop computer. Es-Samaali et
al. [109] proposed a blockchain based access control frame-
work to reinforce the security of bigdata platforms. The key
features included the distributed nature and lack of central au-
thority with transparency, light weight, fine granularity. They
authors defined an authorization token which defines the access
right by the creator of the smart contract. SCPKI [110] is an al-
ternative PKI system with decentralized and transparent design
used with smart contracts on Ethereum blockchain. The main
advantage of the system is to identify the rogue certificates with
he web-of-trust model when they are published. The model en-
ables an entity or authority in the system can verify fine-grained
attributes of another entity’s identity.
Blendcac [111] is decentralized smart contract based access
control solution for devices, services and information in large
scale IoT systems. The authors proposed a robust capability
token management strategy which utilizes smart contracts for
registration , revocation and propagation of access authoriza-
tion. The authors developed a PoC on private blockchain on the
resource constrained devices which is raspberry pi and laptops
and demonstrated the feasibility. Lin et al. [112] presented a
blockchain based fine-grained access control framework for the
Industry 4.0.
Ali et. al [113] proposed a decentralized access model using
blockchain for IoT data using a network architecture naming as
modular consortium architecture. The architecture has in-built
privacy with adaptability for various IoT use cases. The fea-
sibility and deployment considerations for the implementation
analyzed in a performance evaluation of existing blockchain de-
velopment platforms including Ethereum and Monax. Lee et. al
[114] pointed that in the IoT environment, when data or device
authentication information appended to the blockchain, there is
a risk of the information leakage through proof-of-work process
or address searching. They authors applied a zero-knowledge
proof to a smart meter system and enabled the transaction pro-
cessing through disclosing the information such as public key.
They authors also studied the avenues to enhance the anonymity
of blockchain for privacy protection.
3.3.3. Security policy in access control
Security policy is a core regulatory component in any orga-
nization as well as Internet applications. The security policy
defines the required security controls aligned with the organi-
zation’s strategic rules and regulations. The depth of access of
the users for the infrastructure or resources will depend on the
security policy. The centralized security policy and governance
architecture is one of the mostly adopted architecture for most
of the organizations. With the centralized security policy man-
agement, the capability to customization is cumbersome. For an
instance, if the employee promoted to the next level, the scope
of accessible resources required to expand. Customization of
the centralized security policy incurs additional overheads. If
the organization deployed beyond frontiers, the overheads will
be more. Furthermore, there is a risk of manipulation of cen-
tralized security policy without user’s consent.
18

Application Key challenges
Blockchain features
Key benefits
Decentralization
Forge resistance
Transparency
Autonomous execution
Accuracy
Identity Data
Protection:[106],
[107]
•Decentralization
•Access control policy to
the data can be defined by
by data owners
•Transparent access log
Risks cloud data theft X
Central point of failure X
Data access and usage can-
not be observed
X X
Decentralized
Identity
Management: [108],
[109], [110], [111]
,[113], [114]
•Privacy enforcement of
clinical research data
•Eliminated trusted third
party
•Ensured availability
Identity management ser-
vice unavailability risk due
to centralization
X
Data consumption is not effi-
cient in centralized systems
X X
Scalability limitations X
Security Policy in
Access Control:
[115], [116]
•Improved perimeter
security when comparing
with the cloud
•Decentralization and
ensured service availability
•Scalability
The stakeholders may claim
security policy is biased and
favorable due to lack of
transparency
XXX
Prone to human errors if a
human intervention exists
X X X
Performance limitations X X X
Table 7: Summary of Applications of Smart Contracts in Identity Management and Access Control Context
19

Improved Secure Transaction Process
- Identification of fraudulent transactions
- Transaction transparency
- Authenticity of records
- Access control to the users
Smart Contracts in Real Estate Applications
Eliminated Processing Fees and
Commissions
- Decentralization and elimination of third party
- Peer to peer operation doesnot require processing fees
- Reduced operational overheads
Faster Processing T ime
- Eliminated data updating labor overheads on documents
- Automated datare plication over the peers replacing manual
intervention
- Eliminated administrative overheads to control access of the
documents
Figure 5: Smart contracts in Real Estate
The smart contracts promise the autonomous execution of
the program once the predefined conditions met and an ideal
solution for decentralized security policy management. The se-
curity controls can define as programs and deploy in the smart
contracts. The autonomous execution eliminates the overhead
of human intervention in the security policy. The distributed na-
ture of the blockchain based smart contract guarantees that the
execution logic is not being manipulated by either an admin-
istrator or any rogue user within the organization. The decen-
tralization ensures the transparency as well as the availability of
the security policy management system.
Cruz et al. [115] presented a role based access control using
Ethereum smart contracts. The smart contracts used for the cre-
ation of user role assignments and eventually published to the
blockchain. The smart contract provides significant features in-
cluding managing and modifying information as required in a
transparent manner. Outchakoucht et al. [116] proposed dy-
namic and fully distributed security policy implemented with
smart contracts. In addition to that, the authors proposed to
apply machine learning algorithms, particularly on reinforce-
ment learning for dynamic, optimized and self-adjusted secu-
rity policy. The smart contract learns from prior experience
to adjust the optimal security policy. Lyu et al. [117] pro-
posed blockchain based access control mechanism in the in-
formation centric networking context. Ali et al. [118] proposed
blockchain based access control mechanism for conflict of in-
terest domain.
3.4. Real Estate
Commercial real estate industry composed of various trans-
action types such as leasing, rental and purchases with dif-
ferent asset classes including commercial properties, houses,
lands and so on. The government authorities such as national
land registry handle all information of the real estate ownership,
leasing and so on. Transferring ownership and leasing transac-
tions performed with the intervention of few trusted third par-
ties. Such operations are manual and exposed to human errors,
data manipulation risks and extensive processing time.
Smart contracts will be the next generation solution which
will revolutionize the real estate trading industry by a storm
with enhanced security and optimized processing time. An
overview of smart contracts in real estate context displayed in
Figure 5. Table 8 summarizes the applications of smart con-
tracts in the real estate context along with the benefits and chal-
lenges.
3.4.1. Improved secure transaction process
Multiple fraudulent transactions can be identified in the real
estate industry. When the title of the asset, either a land or
house is represented by a printed document, the authenticity of
document cannot be easily verified. There are cases where a
person can fraudulently duplicate the title document and sub-
mit to multiple banks as security asset to obtain a loan. The
authenticity of paper title cannot verify in realtime by the cur-
rent centralized systems. There are cases the land owner sells
a land to multiple people using the duplicated paper titles. The
key problem is that the authenticity of paper title issued by a
trusted third party cannot be verified by the individuals.
Smart contracts eliminate the lead time for a title transfer and
the transparent conditions will hiccup the fraudulent ownership
transfer approaches. The ownership information stored in the
public ledger and the parties such as banks can verify the own-
ership of the security.
Karamitsos et al. [119] examined design of Ethereum smart
contract for the use cases of real estate, which is renting res-
idential and business buildings. The authors proposed that the
smart contract created between landlords/real estate owners and
tenants which verifies that the rental agreement is signed, rental
amount paid on time, and the contract terminated correctly. The
authors also highlighted the improvement of the invoicing pro-
cess through the smart contracts and stated that they need to
asses the same use case with Hyperledger Fabric. Spielman
[120] presented the blockchain application for the land title reg-
istry. The key advantages discussed the elimination of the cen-
tralized database in the land registry with enhanced security.
Since all parties are involved in the consensus, the incapabil-
ity of fraudulent transactions in the land title ledger was high-
lighted. Dijkstra [121] presented different possibilities and con-
straints for the blockchain in the real estate management pro-
cess. The research conveys that blockchain is still required to
improve different dimensions such as government regulation,
standardization and so on. The interviews conducted in the re-
search reflect significant insights such as digitally signing the
lease contracts and monitoring the obligations via smart con-
tracts are the most important applications of blockchain in the
real estate management process.
3.4.2. Processing fees and commissions for transactions
The trust establishment of real estate industry accomplished
with the intervention of few trusted third parties such as govern-
ment bodies and banks. These organizations incur processing
fees and commissions such as stamp duties for their mainte-
nance. The fees are not negligible when the transaction value is
million dollars.
20

Application Key challenges Blockchain features Key benefits
Decentralization
Forge resistance
Transparency
Autonomous execution
Accuracy
Improved Secure
Transaction Process:
[119], [120], [121]
•Transaction authenticity
•Eliminates fraudulent
duplication of ownership
documents
Paper documents can be du-
plicated
X X
Central point of failure X
Authenticity is hard to en-
sure
X
Processing Fees and
Commissions:[122]
•Decentralization enables
peer to peer transfer
eliminating centralized
systems
•Eliminated trusted third
party
•Peer to peer operations
Processing fees are higher
making the transactions are
expensive
X
The transaction costs are
governed by centralized au-
thorities
X X
Centralized operational
overheads
X X
Central point of failure X
Ownership documents in pa-
per can be forged
X X
Extensive Processing
Time: [123]
•Faster operations in peer
to peer
•Transaction data stored in
distributed ledger
•Faster verification
Processing requires updat-
ing on few centralized sys-
tems with extensive time for
processing
X
Dependencies with multiple
parties
X
Costs for different data re-
trievels
X X
Table 8: Summary of Applications of Smart Contracts in Real Estate Context
21

Smart contracts eliminate the requirement of a trusted third
party since the transfer executes the smart contract itself. Elimi-
nation of the trusted third party executes the ownership transfer
in real time without processing fees and will reduce unneces-
sary costs to the consumers.
Oparah [122] highlighted the importance of smart contracts
for elimination of costs incurred by the trusted third party. The
cost is around 1-2% of the total value of the property which is
not negligible. The importance of smart contract and the en-
ablement to transfer the ownership between two homeowners
legitimately without paying for third party verification.
3.4.3. Extensive processing time
Current systems are mostly oriented with the centralized au-
thorities. The centralized organizations handle the documents
related to the ownership of lands such as titles. Sometimes the
documents reside on owner’s district or state local authority.
This type of architecture consume time to deliver documents to
each local authority and update information. In contrast, the
smart contracts will execute in real-time or near real-time to
transfer ownership which eliminates logistics problem and re-
duce costs.
Fernandaz et al. [123] proposed Evareium, which is a smart
contract system for trading commercial property. The investors
can trade ERC20 compliant tokens issued from Ethereum
blockchain and utilize them to fractions of underlying property
assets linked to the tokens. The system provides a faster, re-
liable and transparent platform for trading a plethora of real
estate assets such as commercial properties and hotels.
3.5. eGovernment/Law
Transformation of the government services and legal en-
forcement into the electronic genre grabbed attention by most
of the nations including Europe, Asia, and many other regions.
From the electronic services of government, the stakeholders
anticipate different features. These include trust, accuracy and
improved efficiency as well as user satisfaction. The increased
population and complexity of the human needs escalated the
requirement of automation to cope with enormous demand vol-
ume. Regardless of the service type, the eGovernment solutions
handle personal data of the civilians. Uninterrupted service
availability is also expected by the stakeholders. Blockchain
based smart contracts are one of the most promising solution
with significant features for eGovernment services as well as le-
gal enforcement. Table 9 summarizes the applications of smart
contracts in the eGovernment and Law context.
3.5.1. Enforcement of law
The legal system of any country is complicated and consists
of numerous terms and conditions. In a broader view, almost
all conditions executed with the direct intervention of judicial
personal after a certain assessment. For an instance, if a driver
exceeded 10 percent of the speed limit, there is a predefined
penalty. If he exceeded 20 percent, the penalty is even higher.
The conditional execution intervened with a human. For more
complicated cases, the assessment duration is exorbitant which
can drag upto years. The human intervention exposes decision
to human error. Therefore incorporation of the smart contract
for legal enforcement is important because it enables the au-
tonomous and accurate legal execution. However, all the le-
gal terms cannot develop directly as smart contracts. Some
straightforward terms are possible to deploy as smart contracts.
Raskin [124] examined the smart contracts’ operation and its
position in the existing contract law. The author distinguished
the smart contracts as strong and weak, corresponding to the
costs of their revocation and modification. The author also
highlighted the significance of encouragement of smart con-
tracts by the legislature as another form of agreement. Alexan-
der [125] examined the key tensions between classic contract
law and smart contracts. The author also analysed the align-
ment of powers of government on distributed ledgers without a
central authority. The author suggested two main approaches to
achieve the requirement. Sheilds [126] examined the potential
use cases of blockchain based smart contracts along with their
technical limitations and barriers. The author also described
the legal and regulatory issues associated on the adoption of
smart contracts. The legal changes which should be enacted to
realize the benefits of technology also discussed in the article.
Koulu [127] explained application of self-executory smart con-
tracts and blockchain technologies along with their application
to online dispute resolution. The author described the logic be-
hind smart contracts with a more concrete example on a betting
on weather of a given location. The article provides a further
analysis of legal implications outside its application of virtual
currency.
Levy [128] analyzed in depth the smart contract and its role
to automatically execute the obligations without a centralized
enforcement authority. The smart contract and its implication
for social justice and fairness also discussed in the paper. The
potential weaknesses of the smart contracts in the legal perspec-
tive discussed. Rosa et al. [129] presented application of the
smart contract for the intellectual property protection for open
innovation programmes targeted on small to medium enter-
prises. The users sign smart contracts as non disclosure agree-
ment with timestamping with the corrective actions as required.
The solution provides a smart contract based fine grained intel-
lectual property management for open innovation programmes.
Tietze and Granstrand [130] presented a distributed ledger
based approach to automate the intellectual propert y licensing
payments. Lauslahti et al. [131] analyzed the smart contract
from the perspective of digital platforms and the Finnish con-
tract law. The authors also examined the formation mechanisms
of the general principles of contract law in the application of
smart contracts. The adaptability of smart contracts as the cur-
rent legislation also evaluated. Watanabe et al. [132] proposed
a method of recording the classical contracts. The authors uti-
lized a transaction to evidence the contractor consent and in-
formation. The authors used encryption to keep preserve the
confidentiality of the contracts.
22

Application Key challenges Blockchain features Key benefits
Decentralization
Forge resistance
Transparency
Autonomous execution
Accuracy
Enforcement of Law
by Smart Contracts:
[124], [125], [126],
[127], [128], [129],
[131], [132] , [130]
•Automated, faster, and
accurate legal processes
•Transparency of execution
and conditions
•Unbiased legal execution
Biased execution of law and
order
X X X X
Human oriented assess-
ments are cost intensive
XXXX
The time to conclude on a
decision takes time
X X X
Smart Contracts to
Automate
Contractual
Agreements:[133],
[134]
•Autonomous execution
with improved accuracy
•Eliminated trusted third
party
•Improved transparency of
contractual conditions
Processing fees are higher
making the transactions are
expensive
XXXX
Time intensive operations
for the conditional changes
of contractual agreements
X X X
The contract terms can be
manipulated
XXX
Central point of failure X
Smart Contracts for
Public Services:
[135] , [136], [137]
•Improved security
•Improved user satisfaction
•Eliminated overheads
Labor intensive administra-
tive processes
X X X
Administrative overheads X X X X
Lower citizen satifaction XXXX
Table 9: Summary of Applications of Smart Contracts in eGovernment and Law
23

3.5.2. Contractual agreements
A contract is an agreement made between two or more par-
ties with legal binding and enforceable by law. Contractual
agreements in the business are composed with precisely defined
terms and conditions. The terms and conditions are significant
to the parties on the contract because they will set rights and
obligations as well as price variation clauses for each. Classical
contracts formed with the intervention of a trusted third party
such as the notary. The on boarding of the trusted third party
to form a contract incurs service charges. Most of the times,
the trusted third party is a human and hence the risk of human
error also exists. The terms and conditions can be manipulated
by the third party if required.
The smart contracts are applicable to solve few issues asso-
ciated with classical contracts. The smart contracts eliminate
the requirement of trusted third party and it will eliminate the
service cost of the notary. The terms and conditions can con-
vert into programmable codes and deployable publicly. Terms
and conditions are transparent and guarantee that they have not
been manipulated. Furthermore, smart contracts can take their
decisions of their own. For instance, the imposing penalties can
be defined if the terms and conditions breached. Smart con-
tracts are an ideal solution to replace the classical contracts and
improve efficiency, effectiveness and security.
Frantz et al. [133] proposed a modeling approach that sup-
ports the semi-automated translation of human readable con-
tract representations into computational equivalents to enable
the codification of laws. The translated contracts are verifiable
and enforceable computational structures reside within a public
blockchain. The authors identified the smart contract compo-
nents that correspond to real world institutions and explored
capability based on selected examples. Scheid and Stiller [134]
explained the application of smart contracts to automate the ser-
vice level agreement process by eliminating any third parties
during negotiations with guaranteeing terms agreed upon the
service level agreement will not change. Through the smart
contract, the bureaucratic and manual compensation process is
replaceable by the autonomous contractual process which on
board any untrusted parties together, such as subscriber and ser-
vice provider. The PoC presented in the smart contracts for
compensation of service level agreement using network func-
tion virtualization.
3.5.3. Public services
eGovernment refers to electronic implementation of a
broader spectrum of public services provided by the govern-
ment to the citizens. eGovernment services include issuance of
identification documents, taxation, insurance, utilities, border
control and so on. To establish the trust, most of the eGov-
ernment services developed adapting to a centralized architec-
ture. For an instance, PKI is a vital component in most of the
classical eGovernment service. PKI establish the root of trust
as the root CA. The centralized eGovernment systems have all
of the common issues associated with any centralized systems,
including administrative overheads, the central point of failure,
expensive perimeter security requirements and so on. The smart
contracts will eliminate the major issues mentioned and will
provide a decentralized highly available eGovernment system
with extended transparency.
Mark [135] discussed multiple eGovernment applications in-
tegrated with smart contracts. The author illustrated signifi-
cant use cases such as strengthening international aid systems
with smart contracts. The author also highlighted the capabil-
ity of integration of blockchain technology for other services
such as finance and taxation. Chiang et al. [136] presented a
blockchain and the smart contract integrated system to build the
trust between immigrants and the government. The authors in-
troduced ChainGov, a collaborative decentralized platform for
immigrants, governments, and other institutions that can inform
each collaborative individual about the flow of money as well as
real time visibility of all transactions. They also indicate design
implications and future directions of the work. Bodo et al. [138]
presented a normative analysis of blockchain technology con-
tracts along with the smart contracts and their applicability to
copyright law. The extensive features of blockchain technolo-
gies including trust and decentralization as well as transparency
was highlighted for the compatibility of blockchain with the
fundamentals of copyrights. The authors discussed that sub-
stantial amount of transactions in the copyright domain could
be modeled as if-then rules and eventually into smart contracts.
Gheorghe et al. [137] presented the blockchain technology and
its application for the governance of the music industry along
with smart contracts and cryptocurrency. The authors high-
lighted the applicability of smart contracts for terms and condi-
tions in music industry. In addition to that, the smart contract
and its application for tracking the copyrights of digital content
and its value discussed.
3.5.4. National democracy
Voting is an important event in any democratic nation which
requires the participation of every civilian. The election and
counting process are computerized in some countries. Still,
there are technical hurdles in implementation of entirely elec-
tronic voting systems in some countries. The reliability is a
primary requirement in the voting systems along with the on-
demand auditing and compliance assessment requirement. Fur-
thermore, the scalability is a key requirement with ensured ser-
vice availability. The data privacy and access control are also
mandatory features in the electronic voting systems. However,
there are some limitations in the service values in existing cen-
tralized voting systems. The data access control in the cen-
tralized systems prone the into security risks. The alteration
of the number of votes will raise serious political issues in the
country. The scalability limitations may occur since the number
of concurrent voters may increase upto few thousands in peak
time. The blockchain based smart contracts provide an exten-
sive value addition in the electronic voting systems by ensuring
decentralization, transparency and eliminating a single point of
failure.
Garg et al. [139] presented an empirical review comparative
analysis of the electronic voting systems based on blockchain.
Ayed [140] proposed a blockchain based electronic voting sys-
tem which ensures authentication, anonymity, accuracy, and
verifiability. The solution connected to a database of regis-
24

Smart Contracts for Scalable Resource Sharing in IoT
- Efficient and autonomousagreement process
- Accurate and realtimeexecution
- Fraudulent transactionscan beeliminated
Smart Contracts in Internet of Things Applications
Smart Contracts in Edge Computing
- Economic approach for resource constraint hardware
- Efficient dataexchangemechanisms
- High throughput and low latency compatibility
Smart Contracts for the Enforcement of IoT Security
- Decentralized security with peer to peer security
enforcement
- Single point of failure elimination
- Efficient network traffic consumption
Unmanned Aerial Vehicles
- Capability of intelligent UAV management integration
- Automated operational capability
- Efficient dataexchangewithin restricted environment
Smart Cities
- Elimination of trusted third party
- Automated operational capability
- Scalable connectivity
Miscellaneous Applications of IoT
- Peer to peer operational capability
- Decentralization on data storage
Figure 6: Smart Contract Applications in Internet of Things
tered voters and the committed vote stored in the blockchain
to ensure anonymity and privacy. McCorry et al. [141] pro-
posed Open Vote Network which ensures voter privacy us-
ing Ethereum for board room voting. The proposed system
was tested on the public Ethereum network utilizing e-voting
smart contracts. The voting operation incurs financial cost
due to the blockchain network charge by the Ethereum public
blockchain. Patidar et al. [142] proposed electronic voting sys-
tem based on blockchain. The implementation was performed
using Ethereum blockchain.
3.6. Internet of Things
Internet of Things (IoT) is one of the hottest research areas in
the recent ear of computer networking history. It is anticipated
that billions of devices will be connected in future industries.
Many new requirements are identified in different dimensions
to facilitate these IoTs. The automation is an essential require-
ment with the IoT devices in future networks. Improvement
of security is also challenging. The requirement of autonomous
resource sharing will be a key feature of the next-generation au-
tonomous systems. Blockchain based smart contracts will ad-
dress many of these challenges in the future IoT systems with
its in-built automated and decentralized nature. Smart contracts
can be applied to fulfill many security requirements of IoT con-
text. Fotiou et al.[143] illustrated the opportunities and chal-
lenges of the smart contracts for the Internet of Things. Figure
6 illustrates the applications of the smart contracts in IoT con-
text. Table 10 summarizes the applications of smart contracts
in the Internet of Things context along with the benefits and
challenges.
3.6.1. Smart Contracts for Scalable Resource Sharing of IoT
Resource sharing is a significant requirement in the IoT net-
work. The resource restrictive infrastructure arises the neces-
sity of optimal resource sharing service. The resource sharing
service should not be a resource intensive process. If so, the re-
source sharing process will incur another overhead on the sys-
tem. The cloud-based resource sharing mechanism will incur
additional network traffic and computational cost. The smart
contracts will enable peer to peer resource sharing which is
optimal in computation-wise as well as in the network traffic.
Thus, smart contracts can be the next-generation resource shar-
ing approach in the IoT context.
Wright et al. [144] introduced SmartEdge, Ethereum based
smart contracts for the edge computing as a low-cost and low-
overhead tool for compute-resource management. The smart
contract consists with five different states for transition within
its lifetime. The solution offloads the computation in verifi-
able manner. Zyılmaz et al. [145] described a fault tolerant
standardized IoT infrastructure with distributed storage service.
The data access managed using the trustless blockchain. The
authors used swarm as distributed data storage and Ethereum
as the blockchain platform. Liu et al. [146] proposed a
blockchain-based framework for video streaming with mobile
edge computing with adaptive block size for video streaming
for mobile edge computing. The authors designed a customized
incentive mechanism to facilitate the members including con-
tent creators, video transcoders and consumers. The details cor-
responding to the incentive mechanism encoded as a smart con-
tract. Huang et al. [147] proposed a decentralized blockchain
based solution of trusted IoT data exchange. The authors devel-
oped a prototype which can record transactions in an auditable,
transparent and immutable manner. The prototype developed
using Ethereum blockchain.
3.6.2. Smart contracts in Edge computing
Edge computing enriches the IoT systems in the restricted
environment. The Edge nodes associated with IoT systems
are capable of being offloaded with computationally expen-
sive operations of IoT into themselves. In contrast with cloud
computing, edge computing promises more resource economic
operations. The centralized architecture of cloud comput-
ing generates more network traffic and contains latency. The
blockchchain and smart contracts which operate in a decentral-
ized architecture fit into the Edge computing context for future
IoT systems. The peer to peer connectivity eliminates extensive
network traffic and latency. The throughput can be increased
with the deployment of blockchain based smart contracts with
Edge computing deployment model.
Xiong et al. [148] introduced an economic approach em-
powered with a novel concept of edge computing for mobile
blockchain. The authors pointed out that multiple access mo-
bile edge computing is regarded as an auspicious solution to
solve the proof-of-work puzzles for mobile users. The authors
used Ethereum blockchain platform for the prototype system
developed. Stanciu [149] presented ongoing research on ap-
plication of blockchain based smart contracts for the platform
of hierarchical and distributed control systems adopted to IEC
61499 standard. The author used Hyperledger Fabric as the
blockchain solution and the smart contracts were used to imple-
ment the function blocks. The system adopted microservices
architecture with utilization of docker and kubernetes. Yang
25

et al.[150] proposed a data exchange prototype for smart toys,
which empowered with modern edge computing technologies.
The solution developed as a prototype of Hyperledger Fabric
v1.0. The authors used the smart contract to ensure the data
exchange mechanism is efficient, secure and reliable.
Samaniego and Deters [151] presented a novel idea which
proposed to encapsulate the features of blockchain, including
smart contracts in software-defined components and distribute
them towards edge devices. The smart contracts are deployed
in deices called edge miners. The solution is ideal for the com-
putational resource constrained environment. Xu et al. [152]
proposed a blockchain based service provisioning mechanism
for the protection of lightweight clients, such as the resource
constrained IoT devices. The authors proposed to utilize the
smart contracts to help the lightweight IoT clients to validate
the acquired services and corresponding edge servers which
will reduce the computational overheads for the IoT devices.
The authors ensured high throughput and low latency by adopt-
ing efficient permissioned blockchain with the consensus en-
gine which uses proof of authority. Ioni et al. [153] proposed
a blockchain container based architecture which is aligned with
W3C-Prov data model. The used Hyperledger Fabric as the
blockchain platform. The significant activities such as the node
joining, identity check and record provenance are implemented
as smart contracts with the support of Hyperledger Composer.
3.6.3. Smart contracts for the enforcement of IoT security
Security is a crucial requirement in the IoT context. With the
resource restricted hardware, it is extremely hard to enforce se-
curity by increasing the key sizes with multiple cryptographic
operations. The devices are constrained in the form of compu-
tational power as well as memory. Hence utilization of public-
key certificates will be an expensive operation to the IoT de-
vices. The PKI systems may require verification through the
requests sent to the cloud servers which will generate the net-
work traffic. The access control and privilege definition on the
centralized servers will be vulnerable. Overall, the blockchain
enables the stakeholders to embed access control policy on the
smart contracts and deploy in a decentralized manner. The code
is immutable and free of being modified in contrast with the
cloud computing environment. The decentralized operation en-
sures that no extensive network traffic will be generated when
the security is being enforced.
The trust management of IoT ecosystem is vital security con-
sideration. The mission critical application contexts such as
healthcare, smart cities, and vehicular networks require high
end trust establishment for the IoT nodes in operation. The trust
management includes the different services such as the trust es-
tablishment, realtime trust assessment, trust withdrawal upon
the malicious practices and so on. The future IoT infrastructure
will connect billions of devices in realtime and the trust man-
agement frameworks expected to scale up aligning the massive
connectivity requirement. The centralized trust management is
challenging with the future demand expectations. In addition to
that, the computational resource restrictions shift the highlevel
IoT infrastructure design decisions towards decentralized archi-
tectures such as edge and fog computing based designs. The
distinguishing features of the blockchain based smart contracts
promise significant value additions to the classical trust archi-
tecture, addressing the limitations of classical trust ecosystems
in IoT.
Fortino et al.[154]initially proposed a method to measure
trust of the automated guided vehicles in the smart factories and
elaborated with a design of framework to exploit the measures
for the formation of virtual, temporary and trust-based teams
for the mobile intelligent devices. The included comprehensive
experimental results which proves the efficiency and effective-
ness optimization capability to improve the performance of the
workshops. [155] introduced a reputation capital model for the
multi-agent systems and integrated blockchain technology to
certify the reputation capital of each agent in each federated en-
vironment. The comprehensive experimental results prove the
usability of the proposed model to detect the misleading agents.
[156] presented a reputation model with blockchain technology
for grouping the agents in IoT. The reputation capital related
operations, including the update of reputation capital managed
through the smart contracts.
Dorri et al. [157] highlighted the significance of blockchain
to overcome the security and privacy challenges of IoT. The
authors stated that the resource intensive consensus operations
of existing blockchain platforms are incompatible in the IoT
context. The authors proposed a lightweight and scalable
blockchain for IoT which utilized a distributed trust method
instead of solving a puzzle in consensus. Yu et al. [158] il-
lustrated that the IoT devices and data will be a trading capable
commodity in near future and the infeasibility of the central-
ized trading platform for such a requirement. The authors stated
that the blockchain based smart contracts will eradicate the re-
quirement of the trusted third party. The authors demonstrated
the establishment of trust by smart contracts and blockchain to
enable end to end trading. Khan and Khaled [159] presented
a survey on major security issues of IoT layered architecture.
The authors outlined the security requirements for IoT as well
as the existing threats, attacks along with the state-of-the-art so-
lutions. The authors highlighted that the blockchain technology
is a key enabler to solve many IoT security problems.
Lin et al. [160] proposed a blockchain based conceptual ar-
chitecture and design to establish trust of the private LoRaWAN
network servers. The proposed solution provides an irrefutable
mechanism which verifies that the data of a transaction existed
at a specific time in the network. The authors also stated the
capability of smart contract technology to define an automated
trading model in the IoT network. Pan et. al [161] designed
and implemented a prototype named “EdgeChain”, which is
an edge-IoT framework based on blockchain based smart con-
tracts. The authors integrated a permissioned blockchain along
with an internal currency system to link the edge cloud resource
pool for each IoT device attached with account and resource
usage. From the experiments and evaluation the authors high-
lighted that integrating EdgeChain is within the reasonable and
acceptable range to gain the security benefits. Cha et. al [162]
proposed the blockchain connected gateways to the protection
of users from sending personal data to IoT devices without the
users’ consent. The gateways proposed by them also store user
26

privacy preference on IoT devices within the blockchain net-
work. The solution contributed to improving privacy and trust
in IoT applications with legacy IoT devices.
Salahuddin et al. [163] proposed an agile softwarized infras-
tructure for IoT with secure and privacy preserving deployment
in smart healthcare services with significant features such as
enhanced security and virtualization techniques. The system
employs smart contracts for seamless and transparent trans-
fer of patient information from machine to machine. The au-
thors have suggested that the integration of legal contracts as
part of the deployed smart contracts can be used for proper en-
forcement and to control misbehaving members. Rantos et al.
[164] proposed a blockchain integrated framework named “Ad-
vocate” which facilitates the GDPR-compliant personal data on
the IoT environment. The smart contracts have been utilized to
define the rules and penalties as well as automatically enforce
the obligations. As future work, the authors plan to develop a
policy-based access control system for the integrated personal
data management system in IoT. Pinno et al. [165] presented
a blockchain based architecture for IoT access authorization
named as “ControlChain”. The authors stated that the archi-
tecture is user transparent, decentralized as well as scalable and
fault tolerant. The authors divided the database of ControlChain
into 4 different blockchains and illustrated clearly. The authors
also provided a secure way to establish the relationship between
users and devices. Liu et al. [166] presented a blockchain-
based data integrity service framework. The data integrity ver-
ification protocols were implemented as smart contracts in the
Ethereum blockchain operated in the private mode. The frame-
work has few advantages including enhanced reliability with
decentralization, improved efficiency with multiple operating
clients along with data trading capability.
Rathore et al. [167] presented blockchain based secure ar-
chitecture in the IoT context. Alphand et al. [168] presented
IoTChain, an improved blockchain based security architecture
with key management and distribution framework. The sys-
tem was implemented on Ethereum blockchain operated on the
private mode. The resource owner describes the access rights
in the smart contract, which will generate access tokens to the
clients when the certain conditions have been met. Nagothu
et al. [169] proposed a smart surveillance system with smart
contract based access control system. The decentralized secu-
rity mechanism was deployed to protect and synchronize data
of the communication channel. The permissions on the data ac-
cess enforced utilizing the smart contracts. Polyzos et al. [170]
explored the potential of a blockchain assisted information dis-
tribution system for the IoT, along with the enforcement of the
key security requirements using blockchain based smart con-
tracts. The authors stated the contribution of blockchain based
smart contracts to the sustainability of the IoT system and the
enablements of new trust models. The proposed system de-
signed for compatible with Ethereum client side architecture.
Roy et al. [171] presents a secure transaction framework in as-
sociation with the blockchain for the IoT QoS.
3.6.4. Unmanned Aerial Vehicles (UAV)
The research and development of UAV evolved with a lot of
strengths which are versatile and applicable in the future indus-
tries. UAVs can be utilized to complete tedious tasks that are
risky and expensive to being fulfilled with humans. The opera-
tional accuracy is highly anticipated in UAVs intervention and
efficient resource consumption is highly concerned. Especially
the battery life is one the major concern in the UAVs. In addi-
tion to that, scalability is required in future UAV systems. The
blockchain based smart contracts will enable decentralized and
peer to peer operation of UAVs which will enhance efficiency
and performance.
Mehta et al. [172] presented a comprehensive survey on the
security issues of 5G enabled UAVs with a taxonomy in 5G-
enabled UAV networks. Kapitonov et al. [173] presented the or-
ganization of a communication system between agents in peer-
to-peer network with decentralized Ethereum blockchain based
smart contracts for UAV. Their previously developed project
AIRA (autonomous intelligent robot agent) takes care of the
formalization of interaction and data exchange between robotic
networks including UAV and smart contracts. The system uses
its own token within the network as well as from the Ethereum
network. Sharma et al. [174] presented the application of
blockchain for drones which act as on-demand nodes for inter-
service operability between multiple vendors. The drone smart
contract includes the rules for initiating and regulating transac-
tions between drones and the vendors. The features and threat
implications of blockchain based smart contract based drones
were also illustrated.
3.6.5. Smart cities
Smart cities are one of major IoT innovations which will use
in future town and country infrastructure development. Smart
cities are anticipated to improve the quality of life. The enthu-
siasts have a lot of inspirations on significant contexts including
entertainment, casinos, integrations with smart vehicles and so
on. Since the smart cities consist of thousands of connected de-
vices, the scalability of the operating platforms is a major antic-
ipation. In addition to that, centralization will incur significant
overheads with additional risks.
Smart contracts and blockchain will play a vital role in the
future of smart cities. The operational capability of the smart
contracts on the decentralized model will add more value with
guaranteed service availability. The peer to peer operational
capability of smart contracts will reduce the network resource
consumption and improve the efficiency along with latency.
Yang et al. [175] proposed a framework of decentralized,
secure and privacy-preserving eGovernment system for smart
cities which utilizes the blockchain technology. The authors
discussed the capability of application of smart contracts as
a replacement of real contracts. The authors highlighted the
adaptation capability of Ethereum platform as an open source
blockchain solution. Liao et al. [176] illustrated the design
and applications of future 5G wireless micro operators in casi-
nos and other entertainment applications in future smart cities.
The utilization of smart contracts in different use cases in-
cluding Mega Jackpot. The authors introduced the concept of
27

Value Network Configuration model to illustrate the smart con-
tract interoperability within devices, micro operator and ser-
vice providers. Lazaroiu and Roscia [177] designed a smart
district model which is a mandatory step to build a smart city
incorporating new technologies and the role of energy manage-
ment system integrated into a blockchain and IoT based plat-
form. The setup utilized smart contracts for autonomous dis-
tributed power grid management by the local community along
with the smart meter technology. The authors highlighted the
blockchain technology as a key element for increased cost com-
petitiveness for the rapid deployment of the smart city.
Leiding et al. [178] proposed to combine the vehicular
ad-hoc network with Ethereum blockchain to enable the sys-
tem with transparent, self-managed and decentralized. Each
network entity, such as Road Side Unit(RSU), Application
Unit (AU) or On-Boarding Unit (OBU) will identify with the
Ethereum address. They stated the advantage of Ethereum’s
solidity programming language’s Turing completeness to pro-
vide wider services including traffic jam updates and weather
forecast. Sun et al. [179] proposed a conceptual framework in-
cluding three important dimensions as human, technology and
organization with fundamental factors for the smart city with
sharing economy perspective as well as the application of the
blockchain in the smart cities. The authors discussed the appli-
cability of smart contracts in the shared economy. The authors
highlighted the trust model based on blockchain based smart
contracts will democratize the relationship between human and
organization. Sharma et. al [180] proposed a vehicle network
architecture based on blockchain in the smart city. The authors
illustrated the application of the smart contract to commit au-
tonomous payments. They expected to incorporate blockchain
and wearable technologies as future work.
Sharma et al. [181] proposed a blockchain-based distributed
framework for the automotive industry which will consist of au-
tonomous and connected cars in the smart city. The authors ap-
plied smart contracts in significant phases of the vehicle lifecy-
cle including registration, leasing, certification etc. The authors
successfully performed a simulation with Ethereum blockchain
platform in the private mode and the results conveyed that the
proposed approach is effective and feasible to build a sustain-
able automotive ecosystem for the smart cities. Su et al. [182]
proposed a contract based energy blockchain for the electric ve-
hicle charging the smart community. The authors utilized smart
contracts to implement the secure charging services once the
valid trading conditions met and for the required cryptocurrency
exchanges. The optimal contracts are analysed and designed to
align with the customized EV(Electric Vehicle)’s individual en-
ergy requirements based on the contract theory.
3.6.6. Miscellaneous applications of IoT
Internet of Things is one of the most promising technology
enablers in the future industrial domain. There is a lot of re-
search in progress by the academia and industry in multiple as-
pects of the IoT context. Most of the architectural designs are
being adopted with decentralization and the peer to peer opera-
tional capability. The efficient resource consumption is highly
anticipated and it is hard to yield significant efficiency when
the devices are operating in a centralized architecture. The
blockchain based smart contracts will resolve most of the is-
sues associated with the centralization and adding a lot of value
additions to the implementation. The IoT data sharing is a sig-
nificant requirement in the different application contexts. The
data sharing techniques expected to enforce access control and
encryption techniques to protect the data over transit. The com-
putational resource restrictions of IoT make the data sharing
techniques challenging with different limitations. Niya et al.
[183] proposed monitoring system integrated with Ethereum
blockchain and LORA (LOngRAnge) technology. The authors
used the blockchain to store and retrieve the data generated by
the sensors. The authors utilized Ethereum lightweight client
which only stores and synchronized the current transactions.
Feng et al. [184] implemented a consortium chain-based out-
sourcing feature extraction scheme over encrypted images inte-
grated with smart contracts and several other techniques in the
device to device communication. The authors utilized smart
contracts to transmission of the encrypted images. The authors
utilized Hyperledger Fabric as the platform for smart contracts.
Biswas et al. [185] proposed a security framework which inte-
grates the blockchain technology with smart devices and pro-
vides a secure communication platform in the smart city. The
authors highlighted the applicability of Ethereum smart con-
tracts to enable the peer to peer functionality. The authors also
stated that the integration of existing communication protocols
with blockchain is challenging. Bahga et al. [186] presented
a decentralized peer-to-peer platform named as BPIIoT for in-
dustrial internet of things which enables distributed applications
for manufacturing. The platform enhances existing platforms
in different dimensions such as enabling consumer-to-machine
and machine-to-machine transactions without a trusted interme-
diary. The implementation was integrated with Arduino Uno
and Ethereum platform in private mode. Ibba et al. [187] pro-
posed CitySense, a blockchain based solution to solve the data
storage and management. The authors applied smart contracts
to enable the management sensor information and control logic.
The authors used SCRUM methodology in development of the
required software in the implementation.
Manzoor et al. [188] presented blockchain based proxy re-
encryption scheme which stores the data in cloud without in-
tervention of a third party. The system established a smart
contract for the data users to control the access to the data.
The proposed scheme evaluated using the Ethereum blockchain
platform. Tharaka et al. [189] presented a blockchain based
lightweight certificate management framework for 5G IoT. The
proposed system utilized the smart contracts for threat scoring
and revocation of the certificates of malicious IoT nodes. The
system evaluated using Hyperledger Fabric blockchain plat-
form. Some futuristic insights on the role of blockchain in 6G
presented in [190].
28

Application Key challenges Blockchain features Key benefits
Decentralization
Forge resistance
Transparency
Autonomous execution
Accuracy
Smart Contracts for
Scalable Resource
Sharing in IoT:
[144], [145], [146],
[147]
•Decentralized service
availability
•Peer to peer scalable
operations
•Accurate agreements
Resource intensive central-
ized operations
X
Lightweight cryptographic
operations are vulnerable
X
Scalability limitations X X X
Manual access control
strategies are hard
X X X X
Smart Contracts in
Edge Computing:
[148], [149], [150],
[151], [152], [153]
•Improved perimeter
security
•Reduced attack risk
•High throughput
Security risks for data in
cloud
X X X
High risks in data transit
over cloud
X
Performance limitations X
Data access control limita-
tions
X X X
Smart Contracts for
IoT Security:[157],
[158], [160], [161],
[162], [163], [164],
[165], [166], [168],
[169], [170], [154],
[155], [156]
•Decentralized security
policy
•Efficient network
consumption
•Scalability limitations
Computational resource lim-
itations
X X X
Network traffic generated
from eneromous number of
nodes
XXXXX
Scalable trust establishment XXX
Higher resource consump-
tion for cryptographic oper-
ations
X X X
Unmanned Aerial
Vehicles:[173],
[174], [172]
•Guaranteed service
availability
•Decentralization
•Optimal network resource
consumption
Computational resource lim-
itations
X X X X
Concurrency requirements
of UAV
X X X
Higher throughput X
Central point of failure X
Smart Cities:[175],
[176], [177], [178],
[179], [180], [181]
•Decentralized service
availability
•Eliminated trusted third
party
•Efficient network usage
Computational resource lim-
itations
X X X
Throughput limitations X
Higher scalability require-
ments
X
Higher data consumption X X
Table 10: Summary of Applications of Smart Contracts in Internet of Things Context
29

3.7. Telecommunication Services
The telecommunication industry plays a vital role in almost
all of the nations in the world. The customer volume inflated
and the complexity of the services widened with the develop-
ment. For the conformance of current and future demands, the
network infrastructure and software modules require upgrading.
The blockchain based smart contracts invigorate the telecom-
munication industry in different dimensions. The enhanced
trust, autonomous execution of blockchain based smart con-
tracts ensure security as well as scalability which is a mandatory
requirement in modern telecommunication systems. Table 11
summarizes the applications of smart contracts in the telecom-
munication context along with the benefits and challenges.
3.7.1. Autonomous and intelligent resource sharing in
telecommunication
The subscribers of telecommunication services are prolifer-
ating with the expansive utilization of mobile devices around
the world. The sophistication of services emerges the com-
plexity in different aspects of the telecommunication domain.
The restricted resources in telecommunication required to al-
locate and utilize in a paradigmatic manner[191]. Further-
more, the subscriber-user agreements with their complexities
must compatible with scalability requirements with future elas-
tic demands. The blockchain based smart contracts are ideal
solutions for the autonomous secure execution of service level
agreements as per the customized subscriber need with scal-
ability. There are many feasible use cases identifiable in the
blockchain based smart contracts for optimal and accurate re-
source sharing in the telecommunication industry.
Raju et al. [192] proposed to use blockchain based spec-
trum exchange and smart contracts to implement elastic hand-
off, which is a composition of conventional cellular and vol-
untary spectrum handoffs. The authors proposed to enforce
user and network accountability via smart contracts. The in-
teractions between different components such as cognitive cel-
lular users, cognitive cellular users and cognitive cellular net-
works and so on. Pascale et al. [193] proposed adoption of
smart contracts to implement simple and effective service level
agreement between small cell providers and mobile operators.
The authors presented example contract based on Ethereum
blockchain. They declared it as a smart contract as a service
to individual users and retail venues. Backman et al. [194] pre-
sented blockchain slice leasing ledger concept with an analysis
with its future application. The network slice trading is per-
formed in the blockchain and its smart contracts order slice or-
chestration from slice broker autonomously. The next phase of
the presented research will focus on the evaluation of slice leas-
ing ledger from business, policy and legal perspectives. Valta-
nen et al. [195] presented blockchain network slice brokering
use case along with value analysis and the results in the indus-
trial automation application scenario. The authors applied the
proposed resource configuration framework against blockchain
based smart contract characteristics and capabilities to assess
the use case value. The use case enabled industrial automa-
tion process to autonomously and dynamically acquire the slice
required for more efficient operations. Fernando et al.[196] pro-
posed a blockchain based wifi offloading platform for 5G. The
smart contracts utilized for Wifi service provider rating and of-
floading decision making.
Yrj¨
ol¨
a [197] discussed the unrivalled challenges of onboard-
ing multiple stakeholders in future 6G ecosystem. A decen-
tralized resource configuration prototype was proposed based
on blockchain based smart contracts. The proposed prototype
offered full autonomous resource configuration via blockchain
as the resource orchestrator, which eliminated centralized re-
source orchestrator. Dai et al. [198] proposed a combination
of blockchain and AI for resource sharing in the wireless net-
works. The proposed architecture provides services on resource
management, flexibility in networking, and orchestration. The
authors further proposed secure content caching environment
utilized with advanced deep reinforcement learning to design
caching scheme. Nag et al. [199] presented a comprehensive
discussion on the security issues in the management of virtual
network functions in the optical 5G networks. The work pre-
sented a high-level overview on the application of blockchain
to eliminate the identified issues.
3.7.2. User identity management and access control with
smart contracts
Identity management and access control is a significant secu-
rity requirement in the telecommunication industry. The iden-
tity management system must be capable to coping with the
futurstic demand inflations of the telecommunication industry.
The identity theft is required to eliminate and essentially the
service availability should be ensured. Blockchain based smart
contracts already being adopted in multiple industries for access
control. The telecommunication industry can empower with the
blockchain based smart contracts for access control implemen-
tation. Furthermore, the decentralized nature will ensure the
service availability with ensured scalability.
Raju et al. [200] proposed a privacy-enhancing user iden-
tity management system incorporated with blockchain based
smart contracts. The two main purposes of the smart contracts
are the enforcement of privacy compliance between cognitive
cellular user and identity and credibility service and establish-
ment of service level agreement between cognitive cellular user
and cognitive cellular network. The experiments with the pro-
posed system carried out on Ethereum blockchain on the private
mode. Pop et al. [201] proposed augmentation of the proto-
col stack including application, transport, network, MAC and
physical layer with the semantic plane, which provides a com-
mon interface for the users, actuators, sensors in one side as
well as the protocol stack on the other side. The smart con-
tracts were applied to control the access of physical resources
in association of smart locks and application level aggregation
of distributed ledger transactions. The key concerns were to
reduce the overhead by incorporating smart contracts.
30

Application Key challenges Blockchain features Key benefits
Decentralization
Forge resistance
Transparency
Autonomous execution
Accuracy
Automated Resource
Sharing in
Telecommunication:
[192], [193], [194],
[195], [197]
•Decentralized and
efficient service availability
•Autonomous agreement
•Improved trust and
scalability
Centralization and single
point of failure
X
Operational overheads X X
Manual agreements are
slower
X X X X
Fraudulent transactions can-
not track
X X X
Identity
Management:[200],
[201], [202]
•Decentralization
•Access control to data
•Reduced overheads
Centralization and single
point of failure
X
Administrative overheads XXX
Data redundancy X
Data privacy issues X X
Roaming
Services:[203], [204]
•Decentralized agreements
•Policy immutability
•Frauds can be identified
•Transparency
Fraudulent activities in
roaming
XXXXX
Centralization and single
point of failure
X
Service unavailability X X X
Table 11: Summary of Applications of Smart Contracts in Telecommunications Context
31

Ling et al. [202] proposed a blockchain radio access network
architecture which manages network access and authentication
in a decentralized, secure and efficient mechanism among in-
herently trustless network entities. The authors applied smart
contracts in multiple scenarios such as user equipment and host
access point agreements on the terms of payments and digiti-
zation of spectrum assets. The authors also enforce the privacy
protection as an additional term to the smart contract and high-
lighted the latency reduction and scalability requirement of the
blockchain.
3.7.3. Smart contracts for roaming services
Roaming is defined as the capability of accessing services
offered by the telecommunication service provider outside the
geographical area of coverage. The services include voice
calls, SMS, data connectivity and so on. Preferebly the ser-
vice charges should be lower than the remote call charges from
the tenant’s current geographical region. The smart contracts
applicable to address some issues associated with roaming and
related services.
Yrj¨
ol¨
a [203] identified the impact of the blockchain technol-
ogy in spectrum sharing concepts using the Citizens Broadband
Radio Service (CBRS) concept as an example. The author sug-
gested that the rules and agreements between the various asset
providing networks can encode as smart contracts. The benefits
of Inter-operator roaming connecting CBRS network by elim-
inating third-party clearinghouse by smart contracts was high-
lighted. Duru and Muhammad[204] emphasized the applica-
tion of blockchain based smart contracts to fulfill the roaming
requirements in maritime industry. The authors highlighted that
there should be a global enterprise blockchain with governance
is required for the success of future utilzation of blockchain in-
cluding roaming. The authors highlighted of the establishment
of policies and standards.
3.8. Logistics Management
The logistics and supply chain industry complexified due to
diversified customer requirements. The global production reg-
ulated according to the economic advantages and most of the
countries contribute to import and export trade. The air and sea
cargo are divers from the break bulk to commodities such as
live crabs, fresh vegetables etc. When the commodities remod-
eled, the storage requirements and environmental condition in
delivery, storage has become a vital consideration. The con-
sumers usually focus whether the specific commodity delivered
to the shelf within the required conditions such as regulatory
requirements. Ensuring the delivery of commodities within the
recommended conditions is a major challenge in logistics and
supply chain. The smart contracts and blockchain technology
promised to solve many problems with its distributed and au-
tonomous executory nature. Table 12 summarizes the appli-
cations of smart contracts in the logistics management context
along with the benefits and challenges.
3.8.1. Ensuring sea/air freight supply chain quality and com-
pliance
Supply chain compliance is a major concern in certain com-
modities such as edible items including vegetables, fruits and
live crab. The standards established by organizations such as
Marine Stewardship Council. The authorities execute robust
audits to ensure that the certified seafood stakeholders ensure
the standards. The extensive cost and effort could be elimi-
nated by enabling smart contracts to takeover the required ac-
tions within the supply chain. For an instance, the specific con-
ditions required to be met for a valid transfer of the custodian
of seafood defined by the regulatory authorities and incorporate
them as a smart contract. If so, the authorities can make sure
the custodian transfers will be executed once the conditions de-
fined by the regulatory authorities met. Therefore the require-
ment of the explicit audit eliminated. The smart contract, as an
immutable program of conditions will ensure the transparency
of conditional execution.
Wang et al. [205] presented the investigation of the way
which will influence the future of supply chain practices and
policies with blockchain and smart contracts. The establish-
ment of trust and disintermediation, traceability and visibility
of the supply chain, and improved data security identified as
the key values added to the supply chain by the blockchain
technology and smart contrcts. In addition to that, the socio-
economic impact of the supply chain by the blockchain based
smart contracts also discussed. Chen et al. [206] proposed the
application of blockchain based smart contracts to supply chain
quality manage . The authors highlighted that the smart con-
tracts can use plethora of optimization techniques to improve
the delivery such as using GPS coordinates and plan the route.
They authors also highlighted the significance of confidential-
ity on the blockchain, which is corresponding to the sensitive
business information. Angwei [207] Illustrated the applicabil-
ity of blockchain based smart contracts to reduce the complex-
ity of supply chain. The automated verification of the business
transaction along with the decentralized distributed ledger en-
sures that all parties have the appropriate privileges on the sup-
ply chain. The PoC was developed using Ethereum platform
and three smart contracts developed which included commit-
ting payments to the relevant parties as required.
32

Application Key challenges Blockchain features Key benefits
Decentralization
Forge resistance
Transparency
Autonomous execution
Accuracy
Ensuring Sea/Air
Freight Supply
Chain Quality and
Compliance: [205],
[206], [207], [208],
[209], [210]
•Transparency of the
milestones
•Automated and error free
tax calculations
•Automated auditability
Incompliant delivery condi-
tions
X X
Customers are not aware of
compliance alignment
X
Auditing of the compliance
is cost intensive
X X X
Forgery in trade documenta-
tion
XXX
Agricultural Supply
Chain Regulatory
Compliance: [211],
[212], [213]
•Automated operations of
environmental conditions
•Transparency
•Immutability of smart
contract conditions
The suppliers can alter de-
livery conditions
X X
Ambiguous compliance re-
quirements
X X
Customers are unaware of
delivery conditions
X
Special Commodity
Supply Chain
Tracability:
[214],[215]
•Reduced overheads
•Publicly available
certificate information
•Automated compliance
certificate generation
Fake validation certificates
of the gemstones/diamonds
XXX
Fake origin manipulations of
gems
X X
Paper records can be de-
stroyed/misplaced
X X X X
Table 12: Summary of Applications of Smart Contracts in Logistics Context
33

Yuan and Wang [208] conducted a preliminary study on
blockchain based intelligent transportation systems. The au-
thors considered blockchain as one of the secured and trusted
architectures for development of parallel transportation man-
agement systems. The authors proposed smart contract pow-
ered ride sharing service. Nakasumi [209] illustrates the ap-
plication of blockchain for information sharing and eventually
identify double marginalization and information asymmetry,
which are significant problems associated in the supply chain.
The authors proposed to program the laws and regulations on
the blockchain itself and enable data owners to access control
on their own data in the supply chain. They also used homo-
morphic encryption on the data as required and plan to improve
transaction search operation on blockchain. Komathy [210] in-
troduced a five-layer framework to incorporate blockchain in
cargo shipping along with role based access control methods
and data analytics. The solution establishes the secure connec-
tivity between financing stakeholders, banks, IoT, logistics and
manufacturing as well as insurance globally in order to view the
shipment. The users can view the transactions from anywhere
in the world and reduce the delay in real time transactions.
3.8.2. Agricultural supply chain regulatory compliance
Organizations such as Food and Agriculture Organization
(FAO) by the United Nations(UN) established significant stan-
dards to maintain on food supply chain. For an instance, the
thermal conditions of the reefer container with vegetables or
foods inside should remain aligned to the predefined standards
within the delivery in order to prevent development of bacteria
and so on. Sometimes, the reefer stevedoring personals should
manually adjust the temperature which is a human resource in-
tensive operation. The cost of manual adjustments of the reefer
temperature conditions eliminated when the smart contracts in-
corporated. The conditions established by the regulatory au-
thorities and the accuracy of the temperature conditions guar-
anteed with the smart contracts.
Ge et al. [211] presents findings from Public Private Part-
nership programme, blockchain for agrifood, which targeted to
derive insights of the implications of blockchain on agrifood,
along with PoC on a use case of table grapes from South Africa.
The PoC pilot demonstrated that the basic information concern-
ing certificates can store in the blockchain based smart con-
tracts. The authors used Hyperleder Fabric blockchain to de-
velop the prototype system. Green [212] explores potential ap-
plications of blockchain to the agri-food market and over differ-
ent sub domains including food safety. The author highlighted
that the obstacles to the connectivity of the real world into the
blockchain required to investigate properly. The author elab-
orated that the government intervention should be elevated in
order to have a successful future incorporation of blockchain in
the agri-food market. Kim et al. [213] introduced Harvest Net-
work, a theoretical end-to end “farm-to-fork” food traceability
solution with the integration of Ethereum platform along with
IoT devices exchanging GS1 message standards. The authors
proposed to tokenize the agricultural assets into ERC-721 to-
kens to transfer within the supply chain. The software designed
of smart contracts on Ethereum blockchain builds a mesh net-
work to improve food traceability, cost savings and improved
efficiency within agricultural supply chain.
3.8.3. Special commodity supply chain tracability
The provenance of history of some commodities is highly
effective on its monetary value. For instance, gemstones and
diamonds are significant examples. Consistent records of the
movement from the mine to the showroom ensure that the gem
was not altered or the records were not modified in transit.
The certificates issued by government authorities are value-
additions to the commodity. The decentralized and transparent
nature of the blockchain are the ideal fit for the requirement of
special commodities track and tracing.
Cartier et al. [214] provides significant insights of the appli-
cability of blockchain based smart contracts to the gemstone,
diamond, colored stone and pearl industry. The essential facts
of a precious stone, such as geographical location and cutting
and polishing specifications required to record in the ledger.
When the monetization of precious stones, the business rules
can define as the smart contract and the precious stones and
asset ownership can transfer once the smart contract conditions
met. Gutierrez et al. [215] illustrated Everledger which is a dig-
ital global ledger which can utilize to provide transparency for
the open market places in the global supply chain. The authen-
ticity of the asset stored among all industry participants. The
solution developed with Hyperledger Fabric blockchain plat-
form.
3.9. Smart Contracts in Cross Industry
There are numerous applications in the smart contracts in
various industries. The trust, autonomous execution, reliability
and accuracy embraced the smart contracts by diverse indus-
tries. Significant applications of smart contracts in cross indus-
try discussed. An overview of the smart contract applications
in cross industrial applications displayed in Figure 7. Table 13
summarizes the applications of smart contracts in the cross in-
dustrial applications along with the benefits and challenges.
3.9.1. Smart contracts in enforcement of IT security in the
industry
Smart contracts are applicable to enforce the generic IT se-
curity standards of the organizations. Essentially, the organi-
zations must ensure their service availability, alignment with
the security compliance standards and so on. The organiza-
tions maintain the in-house IT security standards by installing
firewalls, Intruder Detection Systems and so on. Mostly, the
solutions like firewalls are expensive and operate in central-
ized manner. The distributed architecture of smart contracts
can utilize to enforce the organizational security after proper
customization. The distributed nature and some other features
of the smart contracts ensure the guaranteed operability without
any single point of failure. Rodrigues et al. [216] proposed a
design to mitigate DDoS attacks applying blockchain technol-
ogy and smart contracts. The authors used the smart contracts to
store the source IP addresses required to block. The proposed
architecture can deploy as an additional security measure for
34

Smart Contracts in Edge Computing
- Data integrity and manufacturing workflow compliance
- Trusted maintainance records
- Autonomous exeuction and accuracy with reduced response time
Smart Contracts in Cross Industrial Applications
Environmental Protection
- Trusted operation
- Accurate autonomous operation
- Immutability of the transaction ledger
Construction Management
- Construction workflow compliance with the standards
- Autonomous settlements to the stakeholder
- Peer to peer interoperability
Aviation
- Guaranteed accuracy
- Automated execution
- Improved trust
Energy Trading
- Eliminates intermediary
- Near real- time transactions
- Accuracy
- Autonomous execution
Figure 7: Benefits of Smart Contracts in Cross Industrial Applications
a particular system without interfering with the existing ones.
Shao et al. [217] proposed a framework to enable self-adaptive
log anomaly detection using the smart contracts.
3.9.2. Smart contracts in energy trading
The energy industry has significant benefits from the
blockchain based smart contracts. The significant features in-
cluding accuracy, autonomous execution, the peer to peer op-
erations of the smart contracts empowers the energy market to
enable peer to peer energy trading, smart metering, efficient re-
newable energy production, etc. The applications of smart con-
tracts in the smart energy context emphasize the versatility of
blockchain based smart contracts for the energy industry.
Pop et al. [218] proposed a blockchain based approach with a
distributed ledger to store the energy prosumption information
collected from IoT smart metering devices and enforcement of
smart contracts to programmatically define the required energy
flexibility on the individual prosumer. Furthermore, the smart
contracts utilized to define the associated rewards or penalties
and the rules required to balance the energy demand with the
grid level production. The prototype of the system was im-
plemented on Ethereum. Kounelis et al. [219] presented the
conceptual design as well as the energy grid prototype and con-
trol layer running on the Ethereum platform. The authors pro-
posed to facilitate the communication between two parties us-
ing a middleware application which interconnects the grid with
the smart contract. The authors planned to extend more com-
plex functions such as allow the use of coins and automated
control of transaction fees from each user. Cutsem et al. [220]
presented a blockchain based demand response framework for
the smart buildings. Tanaka et al. [221] proposed a blockchain
based electricity trading system in association with blockchain
based smart contracts. The authors introduced a virtual cur-
rency called EnergyCoin to monetize the exchanged energy.
The authors also stated the capability of smart contracts which
enable micro-transactions between microgrids and further ex-
tensible for appliances.
Danzi et al. [222] proposed a Micro Grid(MG) proportional
fairness control framework for energy trading using smart con-
tracts. The authors utilized Ethereum blockchain platform op-
erated in the private mode. The authors outlined the mining cost
and the communication cost as potential limitations in the pri-
vate blockchain architecture. Cheng et al. [223] a new transac-
tion framework considering in the existing energy market. The
framework is based on the blockchain technology and includes
pricing methods, power transaction system architecture and few
modules in the energy trading system. The smart contracts
were incorporated to enable the system for decentralized trad-
ing when there is lack of trust between trading entities. Man-
gelkamp et al. [224] provides an energy prosumers and con-
sumers a platform to trade local energy without an intermediary.
They operate the blockchain in private mode. The real-life ap-
plicability and technological limitations were highlighted with
their applicability in future research.
Mylrea et al. [225] explored utilization of blockchain based
smart contracts in cyber resiliency improvement and enhance-
ment of security in transactive energy applications. The signif-
icant benefits of blockchain were highlighted including trust-
worthiness and convenience in monetization. The application
of blockchain which helps to optimize network data and record-
ing residual energy at the substation level was one of the sig-
nificant features expected of incorporation of smart contracts
in the energy applications.Malik [226] developed a blockchain
based smart grid for peer to peer energy trading. The perfor-
mance compared using Ethereum and Hyperledger blockchain
platforms.
35

Application Key challenges Blockchain features Key benefits
Decentralization
Forge resistance
Transparency
Autonomous execution
Accuracy
Energy Trading:
[218], [219], [221],
[222]
•Decentralized scalable
service availability
•Peer to peer operation
•Accurate agreements
Performance issues associ-
ated with centralized archi-
tectures
XXXXX
Scalability issues X X
Security vulnerabilities X
Inefficient resource con-
sumption
X
Automotive
Industry:[227],
[228], [229]
•Decentralized trust
•Transparent service
records
•Interoperability
Lack of trust on the service
records
XXX
Service record forgery risk XXX
Future interoperability re-
quirements with smart cities
X
Environmental
Protection: [230],
[231], [232]
•Scalability
•Improved accuracy on
penalties
Scalability limitations due to
resource restrictions
X
Extensive network trafficX
High resource consumption X
Construction
Management : [233],
[234]
•Scalability
•Establishment of trust
through ledger
Computational and power
limitations
XXXX
Concurrent operational re-
quirements
X X X
Higher throughput require-
ments
X
Aviation:[235] •Autonomous and error
free execution of operations
•Decentralized system with
guaranteed service
availability
Risk of single point of fail-
ure
X
Perfect security require-
ments
X X X X
Seamless international inte-
gration requirements
X X
Table 13: Summary of Applications of Smart Contracts in Cross Industry
36

3.9.3. Smart contracts in automotive industry
The automotive industry is highly focused on the research
and development of applicability in new technologies. The key
focused contexts include the accurate and compliant manufac-
turing process, automotive safety, traceability in periodic main-
tenance records, the immutability of records such as mileage
and so on. In addition to that, the automotive safety and inter-
operability with smart cities also highly concerned in the future
of automotive industry. The enthusiasts have a lot of inspira-
tions on the blockchain based smart contracts which enable au-
tonomous accurate execution and operate efficiently in the peer
to peer mode.
Dorri et al. [227] proposed a blockchain based architecture
for the privacy of the users and elevate the security of the fu-
ture vehicular ecosystems. The authors presented the capability
of blockchain for multiple utilities of the automobile industry
including remote software updates, insurance and so on. The
authors also discussed possible attack scenarios and the pro-
posed architecture and its capability to mitigate these attacks.
Brousmiche et al. [228] proposed a blockchain based smart
contract empowered vehicle data and a process ledger frame-
work to streamline the management of vehicle lifecycle and
maintenance history. The solution enables transparency and im-
proves collaboration between stakeholders. The smart contracts
implemented in Solidity programming language, which is by
Ethereum. Bohl et al. [229] reviewed an automotive road safety
case study and demonstrated the feasibility of utilizing private
blockchains in the automotive industry. The blockchain system
utilized for monitoring and logging the behavior of the driver
with in association with the map layers, geographical data as
well as external rules defined by the local governing body. The
significance of the private blockchain highlighted as the faster
processing and enhanced data privacy comparing with the pub-
lic blockchain.
3.9.4. Smart contracts in environmental protection
Protection of the environment is a mandatory requirement
for the future survival of human. There are numerous research
approaches in progress with different avenues to protect the
environment, natural resources and so on. The application of
blockchain based smart contracts is a distinguishing approach
to the future environmental protection context. The researchers
expect to utilize the trust, accuracy, and immutability of the
smart contracts for the environment protection.
Ongena et al. [230] evaluated the applicability of blockchain
based smart contracts to solve problems in waste manage-
ment. The results indicated the significance of preparation for
blockchain based smart contracts for the organization and in-
frastructure for future waste management. The authors pointed
out important problems which can be resolved by blockchain
based smart contracts including payments for the weight of
waste, wrong information etc. Fu et al. [231] proposed
a blockchain-powered environmentally sustainable emission
trading framework for the fashion apparel manufacturing in-
dustry. The proposed system framework was regarded as a re-
liable approach to reduce the carbon emission of the fashion
apparel manufacturing industry. The immutability, automation,
and transparency was regarded as the significant features for
blockchain which are applicable for emission trading for the ap-
parel industry. Lin et al. [232] utilized blockchain based smart
contracts in association with artificial intelligence for the effi-
cient management of water with climatic changes. The authors
utilized the significant features of blockchain including decen-
tralization and immutability to define a public water transaction
record. The ultimate objective is to improve the trust and opti-
mization of use on the water related data.
3.9.5. Smart contracts for construction management
Construction of infrastructure is an essential requirement of
the survival of nation. There are many types of research are
in progress to efficient, collaborative, and effective construction
and support services management. The important aspects of
the construction management including compliance of building
materials to the standards, accurate payments to the contractors
are incurring administrative overheads to the stakeholders. The
blockchain based smart contracts provide a wider scope of ap-
plicability to the construction management.
Cardeira [233] proposed possible significant use cases of the
smart contracts for the construction sector. The author high-
lighted that the smart contracts with cryptocurrencies are ap-
plicable to develop an efficient method for expediting the pay-
ments of the intervening parties. Encryption of funds to enforce
the privacy also discussed. Turk et al. [234] presented some
insights of the potential of blockchain in construction manage-
ment. The authors highlighted that the communication patterns
between intervening parties are the peer to peer which is aligned
with the peer to peer operational modes of blockchain. The re-
quirement of further research into smart contracts for building
information management discussed.
3.9.6. Smart contracts for air traffic management
Aviation is an essential service that almost all nations of the
world contribute. Air traffic management is the most impor-
tant component of the aviation which incorporates a massive
number of operations including flight directions, airport space
allocation and so on. The air traffic management operations
required to perfectly accurate since the lives on board of pas-
senger aircraft are highly dependent on accurate air traffic man-
agement. Therefore, the privacy, availability, workflow compli-
ance and realtime execution are the key requirements in the air
traffic management context. The blockchain based smart con-
tracts provide trust and accurate execution with its decentral-
ized architecture. Therefore, the research organizations have
a lot of anticipations on the applicability of blockchain based
smart contracts for aviation.
Reisman [235] presented an engineering prototype that in-
cludes a design and methodology to mitigate Automatic Depen-
dent Surveillance – Broadcast (ADS-B) related security issues
using blockchain based smart contracts. The design innovation
is using an open-source blockchain platform which is operat-
ing in private mode to achieve the privacy and anonymity of
the aircraft. The framework featured with a certificate authority
and higher-band bandwidth communication channels for shar-
37

ing private information between authorized parties such as air-
craft and authorized members.
4. Technical Challenges and Solutions in Smart Contracts
Eventually, the smart contracts consist of computer programs
and algorithms. The matters related to the computer programs
as well as classical software developement life cycle are ap-
plicable to the smart contracts. The validation methodologies
which are applicable to evaluate the computer programs and al-
gorithms will be applicable to the smart contracts. In addition to
that, there are some significant challenges identified which will
leave gaps in the application functionality. These techniques
will be focused in detail. The summary of the issues and corre-
sponding solutions summarized in Table 14.
4.1. Verification and validation to resolve correctness issues
The deviated behavior from their functional specifications of
smart contracts will be a significant problem in the smart con-
tract applications. The formal verification of a computer pro-
gram ascertains that the particular program is functioning ac-
cording to the formal behavior for the defined inputs and proves
the correctness. Formal verification exists with two level lan-
guage principles. The formal verification can perform on the
language level and on the bytecode level. From unit testing to
application of complex mathematical functions, there is a myr-
iad of techniques utilized in the context. The formal verification
of the smart contract is salient with its operational properties.
The smart contracts are immutable once they are deployed and
cannot patch easily. In addition to that, the smart contracts may
hold financial values in different applications and will be acces-
sible for anyone. Therefore, formal verification is paramount in
the context of smart contracts.
Bhagavan et al. [236] outlined a framework to analyze and
verify runtime safety and functional correctness of smart con-
tracts written for Ethereum in Solidity programming language
using F* functional programming language used in program
verification. The tool verifies the smart contract in different
perspectives including source level functional correctness, low-
level properties such as gas consumption bounds and evalua-
tion of the correctness of the output of Solidity compiler on a
case-by-case basis applying relational reasoning. The authors
assume that the verifier may only have the byte code in the ver-
ification. Bigi et al. [237] presented an approach with game the-
ory and combined models of the formal methods for addressing
future challenges in decentralized smart contract systems. The
authors applied game theory to analyse how the smart contracts
are settled through bargaining procedures and formal methods
for the protocol validation. The combined analysis formally and
quantitatively clarifies the anticipated behaviour of the proto-
col, which entrusted with a deposit scheme. Sergey et al. [238]
outlined the design of Scilla, which is an intermediate level lan-
guage for smart contracts and provides a clear separation be-
tween smart contract communication and programming compo-
nents with a computational model based on the communicating
automata. Their future work consists of defining formal gram-
mar and semantics of language and implementation of Scilla
and verifying number of contracts on a real-world blockchain
platform. Abdellatif et al. [239] proposed a new formal mod-
eling approach to verify the smart contract in its execution en-
vironment. The authors applied this formalism to concrete the
smart contract for name registration implemented on Ethereum
platform. The authors highlighted vulnerabilities to the smart
contracts on the simulated executions and proposed alternative
designs to eliminate the vulnerabilities. Nehai et al. [240] pro-
posed modeling method of Ethereum application based smart
contracts which apply a formal method named as ModelCheck-
ing. The method verifies that the application implementation
is compliant with its predefined specification which is formal-
ized by a set of temporal logic propositions. The authors illus-
trated the approach by applying to a concrete case study from
the energy market. Lahiri et al. [241] present the evaluation of
safety and security of smart contracts developed in Blockchain-
as-a-Service offered by Microsoft via Azure Blockchain work-
bench. The semantic conformance of smart contracts formal-
ized against a state machine model and developed an automated
formal verifier for Solidity. The authors applied their veri-
fier to VERISOL for the analysis of all contracts with Azure
Blockchain Workbench.
38

Technical chal-
lenges
Description Solutions
Correctness issues
It is challenging to patch or version update of the
smart contracts upon deployment. Therefore, it is
essential to verify the behavior of smart contracts
within the intended domain of inputs. The correct-
ness issues identified should be fixed before deploy-
ment of smart contracts.
•Correctness validation [236],
•Formal verification [237], [238],
[239], [240], [241]
Security vulnerabili-
ties
The security vulnerabilities of smart contracts may
expose the entire ecosystem into a massive risk. Es-
pecially, when a public blockchain is considered,
fixing the security vulnerabilities may require to re-
place the codes in millions of nodes. In cryptocur-
rency perspective, the security vulnerabilities may
cause losses of millions of dollars. Identification
of such vulnerabilities save money, time and safe-
guards the entire blockchain ecosystem
•Security analysis [242], [243],
[244], [245], [246], [247]
•Vulnerability identification [248],
[249]
•Automated security testing [250],
[251] , [252]
•Symbolic analysis [253]
•Security bug identification [254],
[255], [256],
•Security auditing [257]
Software bugs
The software bugs are mainly focused to iden-
tify the functionality of smart contracts to fulfill
the functional requirements. However, due to the
distinguishing nature of smart contracts from the
classical software systems, there are different tech-
niques which utilize novel computer science con-
cepts to identify the software bugs.
•Specialized testing frameworks
[258]
•Automated software testing
•AI powered software testing
•Improved software practices
[259],[260]
•Specialized bug detection tools
[261], [262] , [263]
•Bug classification [48]
Data privacy issues
The data privacy is a vital concern in almost all
application contexts. The distributed ledger pub-
licly replicates all transaction data according to the
principles of blockchain. However, such approach
may raise privacy considerations on the transaction
data when the transaction data is extremely sensi-
tive. The different privacy and data access control
mechanisms expected to be enforce in order to pre-
vent data privacy violations.
•User privacy enforcement [264],
[265], [266]
•Smart contract privacy enforce-
ment [267], [268]
•Secure execution hardware inte-
gration [269]
•Secure multiparty computation
[270], [271]
Performance limita-
tions
The performance limitations hinder the applica-
tions of blockchain to the real world applications.
There are many research conducted to optimize the
performance factors, such as increased throughput
and reduced latency to reduce the gap between the
blockchain and real applications.
•Transaction throughput improve-
ments [272], [273], [274]
•Shrading [275] , [276]
Table 14: Summary of technical challenges and solutions in smart contracts
39

4.2. Security vulnerabilities and prevention techniques
The security vulnerabilities expose the systems into different
risks. Since the blockchain systems for the corresponding ap-
plications built on computer programs, the security flaws com-
mon to computer systems expected to investigate and eliminate
for the secure functionality of systems. The re-deployment op-
erations after the fixes of security vulnerabilities are different
from traditional software deployment lifecycle and challenging
with extensive overheads. Especially, when a particular appli-
cation integrated with a public blockchain network, the rectifi-
cation of a fault will be an expensive operation. However, there
are different technologies emerged in parallel to the blockchain
evolution in order to find the software vulnerabilities of smart
contracts.
Atzei et al. [248] analyzed the vulnerabilities of Ethereum
platform, which is popular in the industry. The vulnerabilities
grouped into three classes according to the level they are intro-
duced, as Solidity, EVM bytecode, or blockchain. The authors
highlighted that they expect the non-Turing complete, human
readable languages will resolve some of the issues identified in
future. Lin et al. [242] discussed the security issues encoun-
tered in blockchain and challenges needed to overcome. The
significant security issues and challenges included majority at-
tacks in consensus, forking issues as well as scalability issues.
The authors also highlighted the role of government to define
the corresponding laws for this novel technologies. Manjunath
et al. [245] discussed the blockchain domain and focused on
the possibilities of blockchain security analysis threat occur-
rences which is attracted more hackers’ threats. The authors
highlighted the significance of each issue and their impact. The
authors expected that in future this will be resolved.
Parizi et al. [250] provided a comprehensive empirical eval-
uation on the open source automatic security analysis tools uti-
lized to detect the security vulnerabilities of the Ethereum smart
contracts written on Solidity programming language. The au-
thors tested the tools on ten real world smart contracts. The
results conveyed that SmartCheck [251] is statistically more ef-
fective in automated security testing than other tools evaluated.
Tikhomirov et al. [251] proposed SmartCheck, a comprehen-
sive analysis tool which detects the code issues of Ethereum
smart contracts. The authors evaluated the tool on a massive
dataset of real-world contracts and yielded potentially success-
ful results. They also stated the capability of development of the
tool in future directions including improvement of grammar.
Nikolic et al. [253] implemented MAIAN, which employs
inter-procedural symbolic analysis and concrete validator to
identify real exploits. The tool identifies three main types bugs
as suicidial contracts, which can kill by anyone, prodigal con-
tracts, which can send Ether to anyone and greedy contracts
which does not allow to get Ether to anyone. The tool evaluated
with analysis of one million contracts and flags 34,200 contracts
vlunerable spending 10 seconds per contract. Liu et al. [254]
presented the tool ReGuard, which are usable to identify re-
entrency bugs in smart contracts. It is a fuzzy-based analyzer
which automatically detects the re-entrency bugs in Ethereum
smart contracts. ReGuard iteratively generates random diverse
transactions to test the vulnerability.
Jiang et al. [255] presented ContractFuzzer which is a com-
prehensive fuzzing framework to detect 7 types of vulnerabil-
ities in Ethereum smart contracts. The authors identified few
significant types of attacks s such as gasless send and reen-
trency vulnerability. The authors identified the false negative
rate optimized when comparing with other platforms. Luu et
al. [256] proposed a symbolic execution tool named as Oyente
to find potential security bugs. The tool flagged 8,833 contracts
as vulnerable out of the 19,366 including TheDAO bug which
led to a 60 million USD loss. Liu et al. [257] proposed a se-
mantic aware security auditing technique called S-gram which
are applicable to Ethereum. The authors combined N-gram
language modeling as well as lightweight static semantic la-
belling and to learn statistical regulatories of contract tokens
and to capture high-level semantics such as the flow sensitiv-
ity of a transaction. The authors stated that S-gram is usable to
predict potential vulnerabilities in identify irregular token se-
quences and possible to optimize existing in-depth analyzers.
Brent et al. [246] provided a security analysis framework for
Ethereum smart contracts. It provides an analysis pipeline for
the conversion of the low-level EVM bytecode into semantic
logic relations. The evaluation conveyed that Vandal is fast and
robust as well as outperforming leading state-of-art tools with
successful analysis of 95 of all 141,000 unique contracts with
an average runtime of 4.15 seconds. Suiche [244] presented
Prosity, which is a decompiler which generates readable Solid-
ity syntaxes from EVM bytecode. The decompiled contracts
can perform with static and dynamic analysis as required.
GRECH et al. [277] classified and identified the gas focused
on vulnerabilities found in the Ethereum smart contracts. In ad-
dition to that, the authors presented MadMax, which are some
static programming analysis techniques usable to detect gas re-
lated vulnerabilities with significantly high confidence. The
approach included low-level analysis for decompilation in de-
clerative program analysis techniques for higher level analysis
which validated with 6.6 million contracts. Wust et al. [249]
presented three vulnerabilities affecting Ethereum blockchain
network and client. The authors described three vulnerabili-
ties in consensus, block synchronization and block difficulty.
The authors also suggested possible countermeasures to pre-
vent the attacks discussed. Tsankov et al.[243] presented Se-
curify, which is a security analyzer for Ethereum smart con-
tract. It is scalable, fully automated and capabile of proving
the contract behaviors are safe or unsafe corresponding to a
given property and tested with more than 18k contracts. The
analysis is a two stepped process which includes a symbolic
analysis of contract’s dependency graph to extract precise se-
mantic information and checking for the compliance violation
patterns. Grishchenko et al.[278] presented a complete small-
step semantics of EVM bytecode and formalized a significantly
large fragment of EVM using F*, which is a popular program-
ming language used for similar verification programmed proof
assistant. The authors also successfully validated it against of-
ficial Ethereum test suite. The authors further defined num-
ber of salient security properties for smart contracts. Otte et
al. [279] presented TrustChain, which is a permission-less
and tamper proof data structure for the storage of transaction
40

records. Trustchain included a novel Sybil-resistant algorithm
named as NetFlow which can determine the trustworthiness of
agents online. The Netflow algo agreed upon higher-level busi-
ness logic. The framework significantly outperforms Oyente
with zero false negatives in their data set. Grishchenko et
al. [252] presented EtherTrust which is an automated static
analysis tool of EVM bytecode. This supports scalability up
to larger contracts. The authors tested the tool with Oyente
and observed outperforming results and EtherTrust showed bet-
ter precision on a benchmark rather than state-of-art solutions.
Mossberg et al. [247] introduced an open source dynamic ex-
ecution framework named Manticore to analyse the binaries of
Ethereum smart contracts. The framework provides analysis
to find issues including logic bombs. The API provides flex-
ibility to customize the utilization of framework. Mell et al.
[280]presented usage of cryptocurrency smart contracts to cre-
ate a distributed consensus protocol which can produce a stream
of trustworthy timestamped public random numbers. The main
objective is to eliminate prediction and control attacks. With
the smart contracts, no one can change the published values.
Popejoy [281] described Pact programming language which is
developed for the Kadena blockchain platform. Kadena is a
private blockchain platform that consists of the smart contract
programming language in a human-readable form. The main
feature is the Turing incompleteness which reduces the attack
risk with restricted power of smart contracts.
4.3. Software bugs and software testing
The software testing is an essential practice in the software
engineering. The quality of software codes and their position
with the specification expected to be evaluated prior to the pro-
duction integration. There are different techniques and tools in
the market to identify software bugs and evaluate the quality.
However, some research conducted to develop tools and tech-
niques for the quality assurance of smart contracts specifically.
Liao et al. [258] presented a behavior driven development
framework for Ethereum smart contracts. The proposed work
reduces the testing overheads and make the bug fixing process
more convenient. Gao et al. [261] presented SmartEmbed
which can be used to identify the clone related bugs in solid-
ity smart contracts. The proposed solution supports identifi-
cation of bugs in the individual scale as well as large scale.
Delmolino et al. [260] documented some important insights
from teaching smart contract programming to undergraduate
students in the University of Maryland. The authors exposed
common errors in designing safe and secure smart contracts.
The authors highlighted the importance of fixing these errors in
programming. Destefanis et al. [259] presented a study case
regarding a smart contract library named as Parity. The prob-
lem was due to poor programming practices and 500,000 Ether
which is equal to 150M USD freezed in 2017. The authors
analyzed the chronology of events and identified that the prob-
lem occured due to negiligent programming practices. Wang
et al. [262] introduced a methodological approach to identify
the non-deterministic payment bugs of the Ethereum smart con-
tracts. The proposed solution implemented as NPCHECKER
and tested with 30,000 smart contracts to detect the non-
deterministic payment bugs. The tool further developed to de-
tect the known vulnerabilities of Ethereum. Torres et al. [263]
proposed OSIRIS which is a framework that combines sym-
bolic execution and tent analysis. The proposed solution eval-
uated with a significantly large smart contract dataset, which
includes 42,108 Ethereum smart contracts to identify the inte-
ger bugs. Dingman et al. [48] proposed a formal classifica-
tion for the known bugs in smart contracts using NIST’s bugs
framework. The proposed framework introduced two classes
as Distributed System Protocol (DSP) and Distributed System
Resource Management (DRM).
4.4. Privacy issues and enhancement techniques
The data privacy is a vital concern in almost all applica-
tions. The core principles of blockchain include the public de-
centralized ledger which includes transaction data. However,
these public transaction data may raise privacy issues in the
perspective of data owners. These privacy requirements need
to be addressed carefully without impact on the other features
of blockchain, including performance requirements. The data
privacy enforcement may reduce the gap between most of the
present applications and blockchain for seamless integration.
[282] presented significant insights of different aspects
blockchain technology including general data protection regu-
lation and its applicability on blockchain as an enabler for data
protection. The authors discussed application of permissioned
and permissionless blockchain based smart contracts in associ-
ation with appropriate data controllers. The authors categorized
the two types of solutions in enabling compliance, as integra-
tion of different cryptographical functions and private computa-
tion schemes without revealing contents of transactions and ap-
plication of blockchains as decentralized verification machines.
Juels et al.[283] illustrated the emergence of the criminal smart
contracts which will facilitate to reveal the confidential infor-
mation. The authors illustrated a few issues including theft of
cryptographic keys by criminal smart contracts. Their results
highlighted creating policies and technical safeguarding mea-
sures against criminal smart contracts to ensure the smart con-
tracts’ beneficial objectives.
Kosba et. al[267] presents Hawk, a privacy preserving smart
contracts, which dissipated the privacy hurdle encountered in
Bitcoin and Ethereum as a currency. The authors propose a
framework, which enables a non specialist programmer to write
a privacy preserving smart contract. Hawk guarantees on-chain
privacy, which cryptographically hides the flow of money and
amount from public’s view. Niya et al. [264] demonstrated a
designing and implementation of a trading application which
utilized Ethereum smart contracts. The application is devel-
oped with flexibility in requesting user identity directly by the
seller and the buyer. The user privacy enhanced with other fea-
tures such as time and cost. Chatzopoulos et al. [265] pro-
posed a new architecture for the event based spatial crowd-
sensing tasks in association with the blockchain and technology
with user privacy preservation. The architecture utilizes smart
contracts to allow crowdsensing service providers to submit
their requests, run cost optimal auctions and handle payments.
41

Liang et al. [266] designed and implemented ProvChain, which
is a decentralized architecture for trusted cloud data prove-
nance. Provchain provides significant security features such as
tamper-proof provenance and user privacy. The main opera-
tional phases are provenance data collection, provenance data
storage and provenance data validation which provides tamper-
proof records to enable transparency and data accountability
in the cloud. Al Bassam et al. [268] presents ChainSpace,
which offers privacy friendly extensibility in the smart contract
platform. The platform offers higher scalability than the ex-
isting platform achieved through sharding across nodes using
a novel distributed atomic commit protocol named as S-BAC.
It supports auditability and transparency as well. Kalodner et
al. [284] presented Arbitrum, which is a cryptocurrency system
with smart contracts. Arbitrum’s model is compatible for pri-
vate smart contracts which does not reveal the internal state to
the verifiers who involve in the validation of transactions in cer-
tain circumstances. Arbitrum incentivizes the parties to agree
off-chain on the VM’s behavior which means that the Arbitrum
miners only required to verify digital signatures without reveal-
ing the contract to confirm that parties agreed on VM’s behav-
ior.
Zhang et al. [285] presented an authenticated data feed sys-
tem which is named as Town Crier. Town Crier provides a
bridge between smart contracts and existing websites which are
commonly trusted for non-blockchain applications. The fron-
tend and hardware backend combined with the solution which
is enabled with privacy as required. Cheng et al [286] presented
Ekiden, which combines blockchain with trusted execution en-
vironment. The authors leveraged a novel architecture which
separates the consensus from execution and enabled confiden-
tiality preserving smart contracts in trusted execution environ-
ment. The authors planned to extend their work to enable secure
multi-party computation in future. Yuan et al. [269] presented
ShadowEth, which is a system that leverages a hardware en-
clave to ensure the confidentiality of smart contracts in public
blockchain like Ethereum. The system also ensures integrity
and availability. The authors implemented the prototype using
Intel SGX on Ethereum network to analyse the security and vul-
nerability of the system.
Benhamouda et al. [270] presented a method for making Hy-
perledger Fabric blockchain platform compatible with private
data using secure multi-party computation. The protocol im-
plemented utilizing Yao’s millionaire’s problem and oblivious
transfer. The authors associated a helper server, which sepa-
rates multi-party computation into off-chain. Zyskin et al. [271]
presented Enigma which is a computational model based on
a highly optimized version of secure multi-party computation
named as Enigma which guarantees a verifiable secret-sharing
schemes and ensure confidentiality. The authors used a mod-
ified distributed hashtable to hold secret-shared data with an
external blockchain as the controller of the network to control
the access and identity management. The private components
of the smart contracts run off-chain on Enigma platform and
named as private contracts.
4.5. Performance limitations and performance improvement
techniques
The performance factors are essential considerations in the
application perspective. The performance requirements of high
volume transaction processing are mandatory for applications
such as digital payment systems. The transaction verification
times for the major blockchain platforms such as Ethereum
and Bitcoin hindered the applicability to the retail payments.
In contrast, the payment networks such as Visa provides 7000
transactions per second. However, a lot of research in progress
to investigate techniques to enhance the performance features
of blockchain.
Poon et al. [272] proposed Plasma, which is a framework
for incentivized and enforced the execution of smart contracts
which is scalable upto billions of state updates per second. The
authors proposed to multiparty off-chain channels to hold the
transaction state on behalf of others. The smart contracts held
in the root chain and the Plasma chain maintains the set of bal-
ances in the main chain. Forestier et al. [273] proposed an ar-
chitecture called blockclique, which shards the transactions in a
block graph along multiple threads. A block in a selected thread
only includes transactions assigned to this particular thread.
The blockclique architecture reaches 10,000 transactions per
second and provides protection against a wide range of well-
known attacks.
Zamani et al. [275] proposed RapidChain, which is a
sharding-based public blockchain protocol with a complete
sharding of communication, computation and storage over-
heads. RapidChain utilizes an optimal consensus algorithm
with block pipelining and a novel gossiping protocol for large
blocks. The empirical evaluations suggest that RapidChain can
process 7,300 transactions per second. Luu et al. [274] pro-
posed Elastico, which is a distributed agreement protocol for
permission-less blockchains which enables scalability. The so-
lution automatically parallelizes the computational power for
the mining service. The scalability evaluated by extending the
number of nodes upto 1600 and focused on significant aspects
corresponding to the scalability. Kokoris-Kogias et al. [276]
presented OmniLedger, which is a scalable distributed ledger
with long term security in permission-less operations. Om-
niLedger is designed to enhance the scalability up to the Visa
payment network being adopted with hybrid consensus and
sharding techniques. The authors introduced “trust-but-verify”
concept to increase the performance.
5. Lessons learned and future work
The previous section discussed the significant technical as-
pects and features of smart contracts based applications. This
section extends that discussion by elaborating learned lessons
and future research directions for further improvements. The
Figure 8 portraits an overview of the flow of lessons learned
and future works.
42

Lim itations of the Classical Systems
Lessons Learned and Future Works
- Central point of failure
- Scalability limitations
- Massive connectivity requirements in future
- Security limitations
- Lack of transparency
Emergence of Blockchain based Smart Contracts
- Immutable, decentralized, and transparent ledger of transactions
- Accuracy of smart contracts in service management
- Decentralized availability eliminating single point of failure
- Scalability in the decentralization
Challenges of Blockchain based Smart Contracts
- Legal acceptance
- Data privacy problems
- Latency in transaction completion
- Extensive computational overheads in consensus
- Blockchain platform operational costs
Lessons Learned and Future Works
- Acceptance of blockchain through legal frameworks
- Optimal consensus mechanisms
- On-demand privacy establishment
- Private blockchain platforms
- Designing specialized blockchain platforms
Figure 8: Lessons learned and future work
5.1. Financial Applications
5.1.1. Lessons learned
Different applications of blockchain based smart contracts in
the financial context was discussed previously. However, sev-
eral aspects of blockchain based smart contracts are still re-
quired to be improved further. Governments and governing
institutes still do not fully recommend smart contracts for the
utilization of fund transfers. The lack of regulating capability
in decentralized systems is the main reason for the government
bodies reluctant to fully approve the smart contracts in the fi-
nancial context. Escrow services also have the same decentral-
ization features and still not adopted by the government bodies
for International fund transfers. Eventhough the Bitcoin and
Ethereum are not fully adopted by the government bodies for
fund transfers, the smart contract platforms like Stellar is still
working for the fund transfers beyond borders.
It is essential to reduce the transaction processing time if the
blockchain is used for retail merchant payments. For instance,
Bitcoin and Ethereum take a few minutes for the completion of
transactions which is not preferred to experience in the quick
merchant transactions. The transaction validation time has to
be retained as minimal as possible eventhough the ledger is
evolving with the transaction count. It is mandatory to inte-
grate blockchain platform with mobile devices in order to adopt
more users. For the merchant retail payment systems with smart
contracts, it has to compete with Visa or MasterCard like cen-
tralized high-end payment processing systems. Therefore, the
further optimization of transaction completion requires to be
considered before integrating the smart contracts for financial
transactions. However, the smart contracts will be ideal for
the financial transaction enablement of closed-loop financial
ecosystems such as rural and undeveloped regions.
The decentralized smart contract based KYC systems will be
attracted by the future banks as a single customer data shar-
ing platform. However, if the legal policies can be defined to
regulate the customer data, the trust of the decentralized KYC
systems will be elevated and more customer satisfaction can be
anticipated. For the stock exchange, the smart contracts will be
an ideal candidate since it enables the autonomous operation.
The improvement of the transaction processing time is required
for further adaptation.
For lending and borrowing, smart contract systems can play
a vital role since lending and borrowing does not require a re-
altime operation. The autonomous settlement which can be en-
abled with the smart contracts will be value addition and elim-
inates fraud. The insurance also will be benefited by the smart
contracts by executing the claims autonomously by data inputs
and eliminating frauds. The transparency of the transaction
records will be advantageous when the auditing procedure of
the smart contract integrated systems is considered. The trans-
43

parency can be a drawback also to the financial context since
the transaction records are visible to the public and some cus-
tomers can be discouraged to share the personal transaction de-
tails with the public. The traceability and autonomous execu-
tion will make the audit procedure independent and transpar-
ent. The main features of the smart contract systems are au-
tonomous execution, elimination of third party intervention and
transaction transparency in the financial context.
5.1.2. Future work
The future of financial transactions requires a robust inter-
vention of the governing bodies to regulate the smart contract
based financial transactions. Eventhough the decentralized na-
ture preferred by the stakeholders, the government requires to
monitor and establish rules and regulate to make the smart con-
tract based financial transactions acceptable by the citizens.
The improvements on the consensus anticipated when the smart
contracts on board for the financial transactions. The transac-
tion delays such as Bitcoin and Ethereum has required to elim-
inate if the smart contract based transactions are applying to
retail merchant transactions. The computational resource con-
sumption requires to optimize to eliminate the mining over-
heads in the financial transaction context. The future smart
contract based financial systems required to design with for-
mal auditing procedures and compliant with PCI-DSS(Payment
Card Industry - Data Security Standards) and PA-DSS(Payment
Application- Data Security Standards) standards for global ac-
ceptance. However, operating the smart contract based financial
systems in a closed loop system such as a village, within an un-
banked customer segment will help to identify the drawbacks in
the real world operation. These drawbacks required to correct
before the operation of smart contract based globally accepted
payment systems.
5.2. Healthcare Applications
5.2.1. Lessons learned
The different applications of smart contracts in the health-
care context discussed previously. The patient data protec-
tion and health information management have a lot of inspi-
rations on smart contracts. The access control to the patient
data can implement with the smart contracts with decentraliza-
tion. Elimination of the central point of failure is beneficial
for the mission-critical healthcare systems. Health-information
management applications with the smart contract incorpora-
tion must comply with health data protection standards such as
HIPAA. Privacy highly considered in health data management
systems. In addition to that, the data integrity of protected data
required to ensure utilizing smart contract systems.
The smart contract based data sharing mechanisms must en-
sure privacy and integrity for the data in transit. The accuracy
of the operation of automated patient monitoring and treatment
systems required to improve since the smart contract applied
with life critical operations. The smart contract developed for
healthcare systems must be checked for the bugs, vulnerabili-
ties, and accuracy. The formal verification can utilize to verify
the operational accuracy of smart contracts for the healthcare
systems. The different aspects of the smart contracts must con-
sider such as the stability of the operations on a load, memory
usage on the execution of the contract and so on. The smart con-
tract systems for the future healthcare systems mostly expected
to operate on private mode rather than public blockchain oper-
ation. The data integrity and immutability of transaction data
are the major expectations of smart contracts for the healthcare
systems.
5.2.2. Future Work
The future research of smart contracts focused on the im-
provement of privacy of health information management sys-
tems. The compliance with regulations is a major considera-
tion of the incorporation of smart contract systems for health-
care. The privacy improvement along with the transparency
requirement of blockchain based smart contracts is an impor-
tant research direction. The secure data sharing schemes be-
tween third party organizations such as insurance companies
required to improve the techniques such as oblivious transfer,
secret sharing schemes. The next generation healthcare sys-
tems require synergestic operation with the services of smart
city such as secured data sharing and eGovernment services.
The data provenance respect to the sharing of private medical
data is achievable with the immutable ledger. Since the accu-
racy of smart contracts developed for patient monitoring and
treatment is highly anticipated, the applicability of formal veri-
fication was highlighted previously. The specialized formal ver-
ification methods for the healthcare systems are an important
research area in the future.
5.3. Identity Management and Access Control
5.3.1. Lessons learned
Identity management and access control contexts have nu-
merous applications with smart contracts. The data currently
stored in centralized systems that have many issues associated.
Elimination of the centralization is the main advantage that at-
tracts smart contracts for identity management. The users’ ca-
pability to control the access of their own data improves trust.
The hardware costs for centralized systems such as HSMs can
eliminate through the decentralization. However, the incor-
poration of national identity management systems with smart
contracts will require further amendments in the legal systems.
The legal systems which recognize the digital signatures and
electronic identification are not compatible with decentralized
smart contract-based identity management and access control
systems. Therefore, the regulatory bodies required to enrich
with the operational capabilities, strengths and weaknesses of
the smart contract-based access control system and define them
legally. Then the smart contract based access control systems
are extensible even internationally. The identity data protection
solutions empowered with smart contracts require to ensure that
they have aligned with local identity management standards.
The security policy definitions with the smart contracts are the
ideal use cases since through decentralization, the trust can es-
tablish. The consensus mechanisms and other dependencies re-
quired to be further improved for the efficient operation of iden-
tity management systems with smart contracts.
44

5.3.2. Future Work
The Identity management system will be capable of auto-
mated identity management and access control in future. The
synergetic operation with PKI based existing identity manage-
ment systems will eliminate integration and adaptation hurdles.
The decentralized identity management and access control sys-
tems must ensure the alignment with existing legal require-
ments in identity data protection. The data privacy must be
guaranteed and it may be required to integrate with existing
PKI systems which attached with HSMs. The smart contract
based identity management systems are extensible as the na-
tional identity data repository of citizens. The access can be
controlled by the users and the service providers such as banks,
telecommunication services, and insurance can retrieve the data
from the repository with the data owner’s consent. The data
usage records must transparently available in the ledger to en-
sure the data owner that his data was not transferred to third
parties such as trade promoters and so on. The identity man-
agement systems must interface with the mobile devices which
will enhance the usability of decentralized access control sys-
tems. The data access policy is a subject to define by the data
owners. The consensus and storage systems must design with
scalability provisions since the identity management systems
will expand along with the number of users.
5.4. Real Estate
5.4.1. Lessons learned
The main objectives of smart contracts in the real estate do-
main are to eliminate the trusted third party and reduce the
transaction time. The centralized automated systems may cur-
rently in use and the smart contract-based real estate systems
required to integrate with the existing legacy systems. How-
ever, the real estate information owned by the property owners
must restrict in availability to the public. The property owner-
ship transfer operations required to execute immediately but do
not require to be realtime such as retail merchant transactions.
Thorough attention may not require to optimize the consensus
for the enhancement of realtime transfers of property as per the
merchant transactions.
However, the extensive transaction processing time in some
of the legacy systems in the present required to eliminate. More
improvements required on the enhancement of data privacy, se-
cure data sharing with third parties such as banks and other reg-
ulatory authorities as well as customer-oriented decentralized
access control to the property data. Since the systems are op-
erating in decentralized mode, the computational and storage
overheads as per the centralized systems required reduced and
this advantage should be beneficial to the system users. The ser-
vice fees required to reduce as encouragement to the customers
for the usage of proposed decentralized systems. The legal
recognition and regulation with the government body without
charging fees will encourage the users to adopt the system. The
smart contract systems for the next generation real estate do-
main may require to incorporate with PKI based eGovernment
systems currently in use for the legal recognition.
5.4.2. Future work
The smart contract based real estate systems may need legal
recognition in order to operate as a national real-estate manage-
ment system. To legalize, the existing definitions must be iden-
tified and the smart contract system must be designed with the
provisions for the legal recognition. The integration with exist-
ing PKI based electronic identity is a prudent solution to legally
onboard the smart contract-based real estate system. The gap
between the smart contract system and mobile devices required
eliminated to increase usability. The mobile devices should be
capable of instant verification of the property record such as the
title report. However, the applicable use cases of mobile de-
vices should be identified. Eventhough the system is decentral-
ized, multiple ownership transfers required to eliminate. The
response to the attacks and the availability of the system should
ensure before deployment. The data backup and recovery pro-
cedures must verify for the functionality when the system is
deployed in a production state.
5.5. eGovernment and Law
5.5.1. Lessons learned
The utilization of smart contracts for the eGovernment and
Law related services is advantageous in different dimensions.
Transformation of government services into the electronic form
is one of the key strategic decisions in the national authorities in
order to enhance efficiency and improve data security. The cost-
intensive centralized solutions can eliminate with blockchain-
based smart contracts integrated solutions. The distinguishing
features such as transparency, fairness and autonomous execu-
tion will ensure the trust and attract the users as well as regu-
latory authorities for the smart contracts for eGovernment ser-
vices.
The privacy of data requires to enforce and the access control
policy to the data required to be controlled by the users to obtain
true decentralization. The scalability of the system is essential
consideration since the eGovernment services are national scale
solutions. The systems require to design with the regulatory
bodies also including the service nodes of the blockchain sys-
tem. Furthermore, the branches of government authorities can
further continue with their decentralized domination with the
contribution of block generation. Since transparency is a major
consideration in the smart contracts for eGovernment services,
the programs must be developed with simplicity for a clear un-
derstanding of the users and regulatory authorities.
5.5.2. Future Work
The future of smart contracts for eGovernment services will
improve the quality of human life in different aspects. Essen-
tially, with the development of smart cities in the future, the
blockchain-based eGovernments services will operate in asso-
ciation with the smart cities. The integration of mobile devices
will be a major design principle in the future. The decentraliza-
tion will enable the peer to peer operational modes for the sim-
ple services. The transparent distributed ledger will eliminate
the requirement of auditing as an explicit attempt. The citizens
will have a unique decentralized identity management system
45

that can be interfaced with other eGovernment services such as
utility services, transport, banking. From the users’ perspec-
tive, user experience requires improvement without repeating
the data capture before a government service. The transparency
of smart contracts is the most prominent feature of smart con-
tracts for the enforcement of law. Through transparency, cit-
izens can establish trust. Furthermore, through automation of
smart contracts, will be the most promising solution for auto-
mated fine calculation in legal violations.
5.6. Internet of Things
5.6.1. Lessons learned
IoT will be one of the most prominent application contexts in
the Industry 4.0 revolution. Billions of devices will connect in
future industrial ecosystems. Blockchain-based smart contracts
integrated architectures add a lot of values to the next genera-
tion IoT ecosystems which cannot be obtained by the central-
ized services. The scalability and decentralization anticipated
in the future IoT systems. When the smart contracts integrated
with the systems, the computational overheads required to re-
duce since the resources are constrained in IoT devices. The
consensus functions required further optimization for the smart
contract integration of IoT systems. The integrations of Edge
computing nodes for the smart contract service deployment are
an optimal and secured design principle. Furthermore, the se-
curity requirements including privacy should be properly iden-
tified and addressed for the massive data volume generated by
the IoT systems. The robust security measures required to es-
tablished on the IoT systems such as UAVs in operation to pre-
vent the cyber attacks and eventually with optimal security.
5.6.2. Future Works
The smart contracts with Edge computing nodes will be a
significant design principle in future IoT ecosystems. The com-
putational overheads of a smart contract system, such as block
generation require to handle on the Edge computing infrastruc-
ture. The future blockchain systems required to design with
enabling provisions for the Edge node connectivity. Edge com-
puting integration interfaces should be designed with compat-
ible protocols such as COAP for the existing blockchain sys-
tems. The existing connectivity protocols must be diversified
with optimal protocols such as gRPC. The integration compat-
ibility of future IoT systems must improve since IoT will be a
major contributor in future smart cities.
5.7. Telecommunication Services
5.7.1. Lessons learned
The applications for the blockchain-based smart contracts for
the telecommunication industry still require maturity. The com-
putational overheads and the limitations of the real-time opera-
tion deviate the applicability of smart contracts for telecommu-
nication. However, some services such as slice leasing, spec-
trum sharing mechanisms are still applicable since they are one-
time operations. The smart contracts require further optimiza-
tion if it requires to execute on the resource-constrained devices
such as smartphones. Since the telecommunication services are
large scale operational services, the reliability of the smart con-
tract system requires proper testing. Once the realtime opera-
tional capability of the smart contract systems achieved, more
opportunities can open in the telecommunication context for the
blockchain-based smart contracts.
5.7.2. Future Works
The blockchain-based smart contracts are a blessing solu-
tion for the future of telecommunication since the exponential
growth of subscribers is anticipated with the industrialization.
The enormous volume of mobile subscribers including the in-
dustrial sensors requires the scalability of communication in-
frastructure. Access control to the user data can ensure through
blockchain based smart contracts. The access control system
will enhance the user satisfaction of users. The data reposi-
tories are extensible as the globally accepted identity informa-
tion system for telecommunication service in the future. If so,
multiple MNOs can utilize the smart contract-based user data
repository to eliminate repetitions in customer data capturing.
This data repository can integrate with a smart city ecosystem
and usable to track and trace the activities of users on-demand
for scenarios such as legal actions. The 6th Generation (6G) is
emerging with the promises of higher bandwidth and microsec-
ond latency. The 6G will embrace the blockchain technology
to utilize the decentralization and immutability of ledger in dif-
ferent use cases. The scalability requirements in the future 6G
context will expect to divert from the centralized computational
service architectures.
5.8. Logistics Management
5.8.1. Lessons learned
The main features of the blockchain-based smart contracts
for the logistics and supply chain industry are the data prove-
nance and decentralized autonomous operation. The data
provenance is important to evaluate the alignment of the deliv-
ery with the regulatory requirements of a particular commodity
beyond frontiers. The emergence of IoT infrastructure will in-
crease the usability of blockchain based smart contracts in the
logistics industry. The blockchain based smart contract systems
required to improve further in order to integrate with the logis-
tics systems. The systems required to incorporate with mobile
applications to improve usability. For instance, the supply chain
milestones of agricultural products such as vegetables, fruits,
and fish can store in the blockchain and view the supply chain
to the customers via mobile application. Instead of develop-
ing the blockchain alone, the integration is required to consider.
The efficiency of smart contracts requires optimization in the
autonomous execution enablement of smart contracts in the lo-
gistics context.
5.8.2. Future Works
The blockchain-based smart contracts widely applied for the
data provenance of the logistics and supply chain industry. The
utilization of smart contracts for autonomous operation may re-
quire further optimization. The existing smart contract plat-
forms require fine tuning for the optimal operation. If the smart
46

Figure 9: Future smart contract applications
contract nodes are operating with unstable network connectivity
when the nodes are in the sea, the block synchronization func-
tionality requires to identify. The error handling procedures for
inconsistent blocks due to unstable network connections require
further improvements. The leading smart contract platforms
can fork a specialized version for the logistics-related services
in future use.
5.9. Cross Industry
5.9.1. Lessons learned
Data provenance and autonomous execution are significant
features that utilized widely in the industry. The blockchain
based smart contracts and their utilization for IT security is a
vital application. The decentralized operational capability dis-
tinguishes the blockchain-based smart contracts from central-
ized security solutions such as intruder detection and prevention
systems. The failure risk is minimal with the smart contract in-
tegrated systems in contrast with the centralized solutions. The
energy industry has a significant adaptation of blockchain based
smart contracts since the autonomous execution can utilize for
a lot of use cases such as smart metering, energy trading and so
on. The supply chain use cases such as automotive industry and
environmental protection are mostly dependent on IoT infras-
tructure. The improvements required for IoT will be effective
for the agricultural and special commodity supply chain trace-
ability and data provenance use cases. The lower response time
with highest accuracy is required when the smart contracts are
applicable to mission-critical services like aviation. The testing
procedures such as formal verification, load testing, vulnerabil-
ity assessment requires to conduct thoroughly when the smart
contracts are incorporated to the industry like aviation.
5.9.2. Future Works
There are more opportunities in the industry for the
blockchain based smart contracts. A lot of research-in-progress
to explore more avenues of smart contract applicability. The
improvements of smart contracts such as reduced latency,
higher throughput and scalability will attract smart contracts
to many industries. The industries such as space research and
the military will have more opportunities for blockchain based
smart contracts.
5.10. Emerging Applications of Smart Contracts
The applicability of smart contracts in the different sectors is
an interesting research topic. The features of blockchain based
smart contracts enable a great number of applications to be inte-
grated with in future. The applications which have potential in
future blockchain integration discussed. The Figure 9 portraits
the future context of smart contracts.
5.10.1. Transportation
The blockchain based smart contracts have a disrupting ap-
plicability to the transport industry. The taxi and ride sharing
is a significant example. When comparing with the central-
ized taxi services, the decentralized operational capabilities of
the smart contracts provide scalability of the service with en-
sured service availability. The decentralized distributed ledger
provides transparency of events which is eventually usable in
dispute resolution. The autonomous execution provides effi-
ciency and minimizes the human intervention in most of the
operations such as booking and settlement processes. The trans-
parent ledger provides accountability which is expected in the
transport sector in some cases. However, the privacy and ac-
cess control required to be implemented in the integration of
the blockchain for ride sharing.
5.10.2. Trade forecasting
The trade prediction plays a vital role in the international for-
eign exchange and commodity markets. The prediction frame-
works developed with the market insights and mostly integrated
with machine learning techniques. The centralized machine
learning techniques have limitations in the scalability and there
are privacy concerns in the training data. The smart contracts
can be incorporated for the trade prediction frameworks in fu-
ture to eliminate most of the drawbacks encounter in the cen-
tralized techniques. The decentralization enhances the depth
of crowdsourcing insights for sharp prediction frameworks.
Furthremore, with the incorporation of decentralized machine
learning techniques such as federated learning, the prediction
frameworks can be further fine tuned for accurate predictions
in the future.
5.10.3. Outdoor sports management
There are diverse hidden opportunities in the sports which
can be utilized with the smart contracts for the improvement
of service. The blockchain and smart contracts are applicable
to the data provenance of the sports memorabilia, such as au-
thentic jersey and head gears . The authenticity is verifiable
47

using blockchain. The Non Fungiable Token (NFT), which is a
non-interchangeable token is usable to represent the authentic
assets. The blockchain based smart contracts are further ap-
plicable to store the historic performance data of the players.
This is important when the players transform from the national
contests to the international events such as Olympic games.
The historic records of the performance in games with ensure
the compliance on the drug testing history of players along
with the access control mechanisms powered by the blockchain
based smart contracts. The indirect services, such as telecast-
ing access rights can be managed through the smart contracts in
sports.
5.10.4. Charity
Charitable organizations operate to improve the social well-
being for the needful people in the world. Mostly, the cost in-
tensive requirements such as subsidizing the poor people, needs
of the children fulfilled by the donations of the public. Pub-
lic donations such as automated credit of the accumulated loy-
alty points is currently a widespread approach in fundraising
for the charity. However, the blockchain based smart contracts
improve the transparency in the automated credit of the loy-
alty points for charity. Furthermore, the blockchain provides
fundraising through ICO (Initial Coin Offering) for the charity
organizations. The establishment of smart contracts to utilize
cryptocurrency for the expenses improve the transparency. The
transparency is one of a major advantage in the smart contracts
in the application perspective of charity since the public owes a
right to transparently oversee the expenses of charitable organi-
zations as the public funded them. In the form of dispute resolu-
tion and fraudulent commits of the charitable organizations can
be eliminated through the blockchain based smart contracts.
5.10.5. Human resources management
The capabilities of blockchain and smart contracts for the
context of human resource management eliminate most of the
current issues exist . The distributed ledger provides a on-
demand accessible transparent record repository to track the
significant events of the employees. The employers have on-
demand access to the repository for the background checks of
employees in the recruitment process. The access control to
the data can be established using the smart contracts. Further-
more, the employee payments can be handled through the smart
contracts with transparency and accuracy. The employee pay-
ment handling through the smart contract enhances the value of
employee contracts based on commissions or any other perfor-
mance evaluation criteria. Through the smart contracts, the em-
ployees and employers are visible on the evaluation criteria with
convenience in dispute resolution requirements. The integration
of in-house payment systems with the smart contracts stream-
lines the human resource and financial management workflow
with guaranteed accuracy.
5.10.6. Library services
Eventhough the world is moving towards the digital era, the
reading of books remains sticked with the lifestyle of most of
the people. The libraries play a vital role globally to enhance
the reading. The libraries lend the books to the readers to share
the knowledge. The blockchain based smart contracts have po-
tential to enhance the value of services such as lending. In-
corporation of blockchain based smart contracts can enable the
peer to peer book sharing between members without the inter-
vention of centralized authorities. The compensation for the
delayed returns can be handled by the smart contracts transpar-
ently. The authors are capable of being rewarded as per the
popularity of the publications. The inter-library lending pro-
cesses can be enhanced with the incorporation of blockchain
based smart contracts.
5.10.7. Photography
The application of blockchain based smart contracts open up
many opportunities for the photography. Especially, in the dig-
ital era, almost all the photographs uploaded and shared over
the internet. The blockchain is applicable to store the meta-
data of photographs, such as location information, capturing
hardware, and resolution of the photographs transparently. The
smart contracts are applicable to access control the metadata
for on-demand retrieval and exchanging as per the requirement,
such as for the competitions. Furthermore, the photographs can
be monetized by the integration of smart contracts and enable to
trade in the marketplaces along with processes like auctioning.
5.10.8. Video streaming
The video content and their sizes expected to be exponen-
tially expand in the future with emerging technologies such as
VR(Virtual Reality), 360 degree videos and ultra high definition
in future. The number of video streaming service subscribers
will be increased with diversified video content in the future.
The centralized video streaming servers will have limitations in
the scalability to serve the future requirements. The streaming
from centralized servers will incur costs for the internet service
providers. The streaming lags from the centralized servers may
reduce the nature of the content. Furthermore, the access con-
trol and rights management of the content creators from cen-
tralized servers will expose to central point of failure.
The blockchain based smart contracts can facilitate the ser-
vice with decentralization with efficient data consumption in
streaming. The content rights management and subscription
of the premium content are easily manageable with the decen-
tralized smart contracts. The customized advertising based on
user preference and the location efficiently managable through
blockchain based smart contracts.
5.10.9. Gaming and entertainment
The eSports market is expected to boom with millions of
users in future. The eSports will encounter the scalability lim-
itations in the incentivization, user identity management, and
access control related operations with the rapid growth of de-
mand. The blockchain based smart contracts will improve the
player identity management, access control and provide trans-
parency to eliminate dispute resolution in any case. The fan
incentivization can be handled easily with the tokens supported
by the blockchain. The tokens can be used to trade the mone-
tized components of eSports. Furthermore, the entertainment
48

techniques such as casinos can be regulated and audit with
the incorporation of smart contracts. The dispute resolution is
straightforward when the smart contracts incorporated.
5.10.10. Weapon and ammunition tracking
Weapons and ammunition is utilized in domestic and national
scale in some countries. The accountability of guns, volume of
ammunition, their licensing information and the usage statis-
tics are significant information on the establishment of national
security. The blockchain based smart contracts provide trans-
parency in the license information, usage statistics, ownership
information of the guns with decentralized access control to
the regulatory authorities such as Police, government admin-
istrative authorities and so on. The regulation of the usage
in the national and international scope is also possible with
the blockchain based smart contracts. The authorities such as
United Nations can define the smart contracts to regulate the us-
age of ballistic missiles and rocket launchers as an international
governing body.
6. Conclusion
The paper provides an extensive survey on applications of
blockchain based smart contacts. The significance of smart con-
tracts is distinguished due the rich set of features such as de-
centralization, forge resistance, transparency, autonomous ex-
ecution, and accuracy. As a result, blockchain based smart
contracts are used in wide rage of applications domains such
as financial, healthcare, eGovernment, IoT, telecommunication,
logistics, and different industrial contexts. Several blockchain
platforms such as Ethereum, Hyperledger Fabric, Corda, NEM,
Stellar, and Waves are available to deploy smart contacts with
unique applicability features into the industry. Moreover, it is
expected that more platforms will be emerged targeting special-
ized application domains.
However, there are few challenges that smart contracts have
to resolved before the large scale deployments. These chal-
lenges includes scalability, data privacy, lack of governance,
computational overheads, storage overheads, and network over-
heads. Future research on smart contracts should be focusing
on these challenges. The future research avenues are available
to investigate the optimizations of consensus mechanisms, data
usage efficiency, lower latency, minimal storage overheads with
extremely lower latency in transaction processing.
Acknowledgement
This work has been performed under the framework of 6Gen-
esis Flagship (Grant No: 318927) and SECUREConnect (Se-
cure Connectivity of Future Cyber-Physical Systems) projects.
Moreover, this work is party supported by European Union in
RESPONSE 5G (Grant No: 789658)
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