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A Privacy Preserving Hybrid Blockchain based
Announcement Scheme for Vehicular Energy
Network
Abid Jamal1, Sana Amjad1, Usman Aziz2, Muhammad Usman Gurmani1, Saba Awan1, Nadeem Javaid1,∗
1Department of Computer Science, COMSATS University Islamabad, Islamabad 44000, Pakistan
2Department of Computer Science, COMSATS University Islamabad, Attock 43600, Pakistan
Email: abid.jamal.turi@gmail.com, sanaamjad702@gmail.com,
usmanaziz91@gmail.com, usmankhangurmani@gmail.com, sabaawan046@gmail.com,
∗Corresponding Author: nadeemjavaidqau@gmail.com; www.njavaid.com
Abstract—The vehicular announcement is an essential compo-
nent of the Intelligent Transport System that enables vehicles
to share important road information to reduce road congestion,
traffic incidents, and environmental pollution. Due to the multiple
security issues like single point of failure, data tampering, and
false information dissemination, many researchers have proposed
Blockchain (BC) based solutions to ensure data correctness and
transparency in the vehicular networks. However, these schemes
suffer from high computational cost and storage overhead due
to the use of unsuitable BC on the vehicular layer, costly au-
thentication schemes, and inefficient digital signature verification
methods. Moreover, the privacy leakage can occur due to publicly
available reputation values and lack of pseudonyms update
mechanism. In this paper, we propose a privacy-preserving
hybrid BC based vehicular announcement scheme to enable
secure and efficient announcement dissemination. We use IOTA
Tangle to enable the benefits of BC on vehicular layer while
reducing the storage and computational cost. We employ Elliptic
Curve Cryptography based pseudonym update mechanism for
hiding the real identities of vehicles. To prevent false information
dissemination in the network, we propose a reputation-based
incentive mechanism for encouraging the users to provide honest
ratings about the announcement messages. Furthermore, we use
Cuckoo Filter to enable lightweight trustworthiness verification
of the vehicles without revealing their reputation values. We
also employ a batch verification mechanism to reduce the
delays caused by digital signature verification. Moreover, we use
InterPlanetary File System, and Ethereum BC for ensuring data
availability and secure trust management.
I. INTRODUCTION
Intelligent Transport System (ITS) plays a prominent role
in enhancing smart cities by reducing traffic congestion and
roadblocks and providing efficient routes to drivers. One of the
ITS applications is Vehicular Energy Network (VEN). VENs
are based on standards of Mobile Ad-hoc Network (MANET)
and they enable vehicle to vehicle (V2V) and vehicle to
infrastructure (V2I) communication for energy trading and
dissemination of useful information about road and weather
conditions, roadblocks, alternative routes, etc. Vehicles in
VENs are equipped with an On-Board Unit (OBU), which
uses Dedicated Short-Range Communication (DSRC) protocol
for communication. Along with many benefits, VENs are also
vulnerable to different attacks like Single Point of Failure
(SPoF), false information dissemination, privacy leakage, etc.,
due to the open and trustless environment. To overcome these
issues, several researchers have proposed Blockchain (BC)
based solutions for VENs.
In recent years, the Distributed Ledger Technology (DLT) has
gained immense popularity in academia and industry due to its
features like transparency, non-repudiation, tamper-resistance,
etc. BC is a widely adopted DLT in which transaction data
is stored in cryptographically linked blocks. The set of linked
blocks is considered as a distributed ledger and it is shared
with all the network participants. BC was initially introduced
by Satoshi Nakamoto in 2008 as a backbone for the first ever
digital currency named Bitcoin [1]. In BC, new blocks are
added to the chain by the process of mining. BC provides
captivating features like non-repudiation, data transparency,
data availability, tamper-resistance, etc. Due to these features,
BC is applied in many different sectors like healthcare, smart
cities, supply chain, vehicular networks, etc.
Recently many researchers have employed BC to overcome
the trust and security issues of the traditional VENs. Besides
the many benefits of BC based VENs, it is susceptible to
many potential flaws, which can limit the efficiency of the
vehicular networks. Many of the existing BC based vehicular
networks use Ethereum BC on the vehicle layer [2], [3], which
increases the storage and computational cost on the vehicles.
Some researchers have used Directed Acyclic Graph (DAG)
based DLT named IOTA Tangle in vehicular networks [4],
[5]. As IOTA Tangle relies on data pruning method for saving
storage space, it can cause data unavailability due to which
malicious users can repudiate sharing false announcements
in the network. Generally, in BC based vehicular networks,
pseudonym mechanism are used to preserve the vehicles’
privacy [6], [7]. However, due to use of static pseudonym
identity, the real identities of the users can be inferred by
background knowledge attacks. These attacks are overcome
by pseudonym update mechanism [8]. However, due to lack of
vehicle traceability, the internal attackers can disseminate false
information in the network. To overcome this issue, BC based
reputation schemes are introduced to identify the malicious
users. As the reputation scores of the vehicles are publicly
stored on BC, the adversaries can exploit the predictable
patterns in the reputation values to perform vehicle tracing
attacks.
To address the aforementioned issues, we propose a privacy-
preserving vehicular announcement scheme based on hybrid
BC. In our proposed scheme, we use IOTA Tangle to enable
zero-value transactions, high throughput and low storage cost
on vehicle layer. Moreover, to preserve the privacy of the
vehicles, we use Elliptic Curve Cryptography (ECC) based dy-
namic pseudonyms mechanism to hide vehicles’ real identities.
Also, we use Cuckoo Filter (CF) for hiding the predictable
patterns in the reputation values. To further enhance the
efficiency of the proposed scheme, we use batch verification
scheme to enable simultaneous verification of multiple vehicle
rating messages. In addition, data storage and availability
issues are resolved by using InterPlanetary File System (IPFS).
II. RE LATE D WOR K
A. Authentication
The vehicular networks require a secure and efficient au-
thentication scheme to prevent malicious users from entering
the network. The authors in [9] address the privacy leakage
caused by centralized Public Key Infrastructure. They propose
a distributed pseudonym management system that allows the
users to create their own pseudonyms. However, their proposed
scheme fails to ensure conditional privacy, making malicious
vehicles untraceable. In [2], authors address the issue of
SPoF in conventional centralized authentication scheme in
vehicular networks. They use edge computing and local BC
to efficiently store the registration and trust information of
vehicles to ensure data transparency. However, their proposed
scheme is prone to privacy leakage due to publicly available
trust values. In [6], [8], the authors propose a certificate
revocation mechanisms in vehicular networks to efficiently
manage the Certificate Revocation List (CRL). The CRL is
used for verifying whether a certificate of a certain user is
revoked. The authors in [6] enable privacy preservation in
BC based certificate revocation mechanism by introducing
pseudonym shuffling mechanism. Moreover, authors in [8]
reduce the cost of CRL management by using an efficient data
structure called Merkle Patricia Tree. However, due to the use
of inefficient signature verification mechanism, both schemes
add unnecessary verification delays.
B. Trust Management
In [10], authors propose a BC based incentive scheme to
motivate the users to share important traffic information in
the network. However, their proposed scheme is vulnerable
to privacy leakage due to the use of static pseudonyms.
The authors in [11] propose a privacy-preserving incentive
scheme to encourage user participation while preserving the
privacy. They develop an anonymous vehicular announcement
aggregation protocol to prevent unique identification of a
vehicle in network. However, in addition to the delays due
to inefficient message verification, this scheme also suffers
from an overwhelming storage cost due to inefficient key
management. Moreover, in [12], authors address the security
and trust issues in BC based Industrial Internet of Things. They
use a monetary incentive mechanism to encourage the honest
contribution. However, due to the lack of a batch verification
mechanism, their proposed scheme suffers from unnecessary
verification delays. In [13]–[15], authors address the trust and
authentication issues in Internet of Vehicles. They propose a
decentralized trust management scheme based on Hyperledger
Fabric to store the nodes’ trust values. However, due to the
open availability of trust values, this scheme is vulnerable to
tracking attacks and privacy leakage. In [16], authors propose
a consortium BC based data and energy trading scheme to
enable decentralized trading. They use bloom filters to prevent
data duplication and smart contracts to overcome trading
disputes. In [17], authors propose a BC based food supply
chain management scheme to enable users’ trust and ensure
products traceability. They use smart contracts to store the
records in an immutable manner.
C. Privacy
The privacy preservation is of utmost importance in a vehic-
ular network. The lack of privacy can allow malicious users to
perform vehicle tracking attacks. In this regard, authors in [7]
address the false information dissemination in vehicular net-
work due to the lack of conditional anonymity. They develop
a BC based pseudonym mechanism to hide the real identity
of the vehicles. However, due to the use of centralized cloud
server for storage, their proposed model is vulnerable to SPoF.
Moreover, authors in [18] developed a pseudonym mechanism
that allows vehicle users to generate and update pseudonyms
for themselves without CA’s intervention. However, the self-
generated pseudonym scheme can allow malicious vehicles to
spam the network with false information.
D. Efficiency
In [3], authors propose Proof of Event consensus mechanism
to reduce consensus delays and ensure the validity of the
events shared by the vehicles. However, their proposed scheme
is susceptible to privacy leakage. In [19], authors develop
a joint Proof of Stake and modified Practical Byzantine
Fault Tolerance consensus algorithm for reducing the resource
requirement to perform consensus. However, in their proposed
scheme, privacy leakage can occur due to unrestricted access to
the reputation values. In [20], authors address location privacy
leakage in the smart parking applications due to publicly
available location data of the users. Moreover, they address the
issue of the existing centralized smart parking schemes that are
vulnerable to SPoF. The authors use group signatures, bloom
filters, and vector-based encryption to enable anonymous au-
thentication and malicious users’ traceability. However, their
proposed scheme lacks a reputation mechanism which makes
the system vulnerable to the internal attacks. Moreover, in the
proposed scheme, an unsuitable BC is used on the vehicular
layer. The conventional BC schemes are not suitable for the
vehicular layer due to the resource constrained OBU of the
vehicles. The authors in [10], [21], use IPFS to efficiently store
the transaction data. They also use a reputation management
system to store the reputation values of the vehicles. However,
their proposed scheme is susceptible to privacy leakage due to
openly available reputation values and static pseudonyms. In
[22], [23], authors have utilized consortium BC to store and
share the data efficiently. However, these schemes lack batch
verification mechanism and use unsuitable BC on the vehicle
layer. In [4], authors address high cost of storing BC ledger on
vehicles in vehicular social networks. They use a DAG based
DLT on vehicle layer to efficiently reduce the storage cost of
the ledger on vehicles. However, their proposed scheme does
not preserve the privacy of the vehicles which can lead to
reduced user trust.
III. PROB LE M STATEM EN T
In [24], [25], BC based announcement schemes are pro-
posed to enable secure and trustworthy announcement dissemi-
nation in VANETs. However, due to the use of unsuitable BC
on the vehicle layer, these schemes incur excessive storage
and computational cost on resource constrained vehicles. In
[4], [5], a lightweight DAG based DLT is proposed for
vehicular networks to overcome the excessive storage cost
of conventional BC. In [4], DAG-chain is used, whereas in
[5], IOTA is used for efficient and distributed storage of the
transaction records on vehicles. However, due to the use of
static pseudonyms in [4], the adversaries can identify a vehicle
by performing background knowledge attacks. Moreover, due
to lack of incentive mechanism in [5], the vehicles are not
encouraged to give honest ratings about their peers. In [26],
ABE-based authentication scheme is proposed to authenticate
the vehicles while preserving their privacy. However, due to
the high computational cost of ABE and use of inefficient
message verification method, this scheme introduces excessive
delays, which can reduce the overall efficiency of the network.
In [12], [25], BC based reputation mechanisms are proposed to
prevent false information dissemination in vehicular networks.
In these schemes, the vehicles verify the trustworthiness of
messages by accessing the reputation scores of other vehicles
available on the BC ledger. However, due to the public avail-
ability of the vehicles’ reputation scores on BC, the adversaries
can trace a vehicle by utilizing the predictable patterns in the
reputation values.
IV. SYS TE M MOD EL
A hybrid blockchain based announcement framework is
proposed to improve efficiency, preserve privacy, and enable
secure communication in VENs. The proposed model consists
of three layers as depicted in Figure 1. The first layer is
IOTA Tangle layer, wherein the vehicles communicate with
each other and with Roadside Units (RSUs) via IOTA Tangle,
which is a DAG based DLT. The second layer is the BC
layer, which consists of RSUs and Certificate Authority (CA).
RSUs are connected to each other via wired connection and
they manage the overall network activities. The third layer
is the storage layer which consists of IPFS. RSUs offload
the excessive historical data to IPFS to reduce the storage
cost and ensure the data availability. The proposed model in
Figure 1 contains a mapping table of the identified limitations
and their proposed solutions. The limitations addressed in
this proposed model range from L1 to L6 and the solu-
tions proposed range from S1 to S7. The L1 refers to the
computationally complex authentication scheme. It is mapped
with the solution S1 using Elliptic Curve Digital Signature
Algorithm (ECDSA) based digital certification scheme. The
L2 refers to the privacy leakage due to predictable patterns
in publicly available reputation information of the vehicles.
This limitation is mapped with S2 using CF for storing the
reputation values. The L3 shows the use of sequential message
verification method, which can cause delays in the message
verification process. The proposed solution S3 overcomes this
issue using batch verification method. L4 indicates the various
shortcomings of the conventional blockchain schemes which
makes them unsuitable for the vehicular layer of the VEN.
These shortcomings include low transaction throughput, lack
of microtransactions and high storage cost on vehicles. S4 and
S7 overcome these issues by using IOTA Tangle and IPFS.
The L5 refers to the lack of incentive mechanism, which can
impede the vehicle cooperation in the network. This limitation
is mapped with the solution S5 using of reputation based
incentive scheme. The L6 refers to the privacy leakage due to
the use of static pseudonym. This limitation is mapped with
S6, which relates to updating the pseudonym on regular basis
to minimize the risk of privacy leakage.
A. Entities
The following is a brief description of our proposed model’s
entities.
1) Certification Authority: In VEN, the CA is an essential
entity which allows only the authorized users to join the
network. The CA is assumed to be fully trusted and secure
against any kind of attacks. In the proposed model, RSUs and
vehicular nodes provide their true identity information to CA
for registration. The CA generates pseudonym certificates for
the vehicles. The CA keeps an encrypted copy of a mapping
between true identity and the pseudonym of the vehicle to
enable conditional anonymity. So that in case of disputes, the
digital certificates of the malicious vehicles can be revoked
and their true identity can be revealed to prevent them from
rejoining the network.
2) Vehicles: In VENs, each vehicle is equipped with an
OBU which enables V2V and V2I communication via DSRC
protocol. The OBU of the vehicles is considered as a tamper-
proof device and is used for storing the private keys of the
vehicles. The V2V communication includes announcements
related to traffic conditions, road incidents, and advertisements
etc. To reduce false information dissemination in the network,
the vehicles provide ratings about the received announcements.
In return, the vehicles receive incentives for giving the honest
Storage Layer
L4 →S7
CA
L1 →S1
L6 →S6
Blockchain Layer
IOTA Tangle Layer
L2 →S2
L3 →S3
L5 →S5
L4 →S4
Fig. 1. Proposed System Model
ratings and punishment for the dishonest ratings and false
announcements.
3) Roadside Units: In VENs, RSUs manage the overall
network by providing different services to the vehicles. RSUs
are connected to each other via wired connection and they have
high computational capabilities. In our proposed model, RSUs
are the part of both, the IOTA Tangle layer and the BC layer.
On IOTA Tangle layer, the RSUs act as full nodes and store
the vehicles’ announcement record shared on Tangle to ensure
data availability. In BC layer, the RSUs act as authorized node
and are responsible for:
•vehicle reputation calculation based on Tangle record and
user feedback,
•adding pseudo-IDs of malicious users to a CF,
•performing consensus,
•batch verification of message signatures, and
•uploading the historical data to IPFS.
4) IOTA Tangle: The conventional blockchain schemes
are not suitable for vehicular networks due to multitude of
reasons including, low transaction throughput, high storage
requirement, lack of microtransaction etc. To overcome these
limitations, IOTA Tangle is used in the proposed scheme.
IOTA tangle is a DAG based distributed ledger technology,
which supports microtransactions, provides high transaction
throughput and reduces storage overhead. In the proposed
model, IOTA is used for storing the announcement sharing
records in a distributed ledger. In addition, it enables non-
repudiation so that vehicles cannot deny sending any an-
nouncement message. Hence, the vehicles only disseminate
accurate announcements in the network.
5) Blockchain: In the proposed scheme, Ethereum BC is
applied on RSUs. The use of BC ensures data integrity,
transparency and immutability. The complete Tangle record
is backed up on IPFS and its hash is stored on BC to avoid
data loss, which may occur due to data pruning on IOTA layer.
Also, the CF generated by RSUs are stored on the BC for trust
verification. The data in BC is accessed via smart contracts.
6) Cuckoo Filter: The CF is a new data structure proposed
in [27] that replaces Bloom Filter as a method for testing
whether an element belongs to a set or not. It uses Cuckoo
Hashing and is designed to store items efficiently while
targeting low false positive rate and requiring significantly
lesser storage space than Bloom Filter.
7) InterPlanetary File System: IPFS is a distributed data
storage system. In IPFS, a distinct hash value is generated for
each file which is then used for file retrieval. In the proposed
model, the historical Tangle data is uploaded to IPFS to enable
system’s scalability and efficiency. Whereas, only the hashes
of the uploaded files are stored in the BC, which significantly
reduces the storage cost.
V. CONCLUSION
In this paper, a hybrid Blockchain based vehicular an-
nouncement scheme is proposed for VENs. IOTA Tangle is
employed to reduce the resource utilization on vehicle layer.
The IPFS is used for ensuring the data availability while
reducing the overall storage cost of the system. The Ethereum
BC is used on the RSU layer to store IPFS hashes of the sen-
sitive data. The ECC-based pseudonym update mechanism is
used to enable conditional anonymity. Moreover, a reputation-
based incentive mechanism is utilized to encourage users
to share the honest ratings. CF are implemented to prevent
background knowledge attacks by hiding predictable patterns
in the reputation values of the vehicles. In the future, the
proposed scheme will be validated through simulations on the
real-world networks.
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