Kaiwen Zhang

• Doctor of Philosophy
• Professor (Assistant) at École de Technologie Supérieure

Blockchain wallets use two primary key generation schemes: non-deterministic (ND) and hierarchical deterministic (HD). ND key generation scheme provides better fund distribution but has issues with backup complexity and memory utilization. HD key generation scheme simplifies the backup process but is vulnerable to privilege escalation and brute-for...

EV charging infrastructures traditionally rely on untrusted centralized infrastructures that pose several privacy and security threats to EVs’ personal information. Targeted advertisements, privacy leaks, selling data to third parties, are among the threats to privacy and security. By utilizing blockchain-based solutions, recent work address the se...

Climate change is a major issue that has disastrous impacts on the environment through different causes like the greenhouse gas (GHG) emission. Many energy utilities around the world intend to reduce GHG emissions by promoting different systems including carbon emission trading (CET), renewable energy certificates (RECs), and tradable white certifi...

The increased charging demand resulting from the rapid development of electric vehicles (EVs) poses various challenges to the stable operation of the distribution network and smart grid. Due to the stochastic EV charging behaviour, the high charging demand at the charging stations (CSs) elevates the load curve which may lead to a spatially imbalanc...

Federated Learning (FL) is a promising solution for training using data collected from heterogeneous sources (e.g., mobile devices) while avoiding the transmission of large amounts of raw data and preserving privacy. Current FL approaches operate in an iterative manner by selecting a subset of participants each round, asking them to training using...

Video conferencing has become an essential tool for working from home. However, poor audio/video quality resulting from unstable Internet connections undermines the productivity of important tasks. Additionally, the static monetization model for ISP networks, which employs third parties, cannot support on-demand and dynamic Quality-of-Service sessi...

Abstract—Blockchain is an emerging technology that has encountered a number of challenges, including forks and low transaction processing rates compared to other payment systems. While sharding was designed to resolve the problem of low processing rates, it also increases the scalability of the network. However, its effect on the probability of for...

There is a natural tendency for many public blockchain systems to undergo forks. When they are resolved, they result in a chain reorganization (reorg) where the transactions from the side fork are discarded. This causes delays since clients are required to wait for more confirmations before processing transactions. In order to improve security, spe...

The digital transformation of business processes faces a major hindrance due to the lack of trust and transparency. As blockchain and other distributed ledger (DLT) are considered key enabling technologies, there is a need for supporting tools which can deploy business models over smart contracts in order to leverage these decentralized platforms....

Byzantine Fault-Tolerant (BFT) protocols are classical algorithms that offer a faster and more energy-efficient consensus mechanism compared to Proof-of-Work (PoW), which is typically used by cryptocurrencies such as Bitcoin. Synchronous BFT systems are hard to implement and vulnerable to attacks that aim to disrupt the synchrony of the system. Pra...

Blockchain smart contracts can only operate on data available on-chain, and face a major challenge of not being able to communicate with the world outside their own network. Blockchain oracles solve this problem by bridging the gap between on-chain and off-chain data. Chainlink is one of the most widely used decentralized oracle network with compet...

With the advent of modern technologies, including the IoT and blockchain, smart-parking (SP) systems are becoming smarter and smarter. Similar to other automated systems, and particularly those that require automation or minimal interaction with humans, the SP system is heuristic in delivering performances, such as throughput in terms of latency, e...

In the last few years, electric utility companies have increasingly invested into transactive energy systems. This trend was primarily caused by the integration of distributed energy resources (DERs) and internet-of-things (IoT) devices into their existing distribution networks. Influenced by the general interest in blockchain technologies, many in...

In this paper, we present a methodology for quantifying the decentralization degree of a blockchain network. To accomplish this, we use two well-known graph models of Erdös-Rény and Barabási–Albert in order to study the blockchain network topology. We then quantify the decentralization degree using the clustering coefficient of our network models....

There is a significant drawback associated with blockchain networks in terms of their processing speed, which is one of the biggest. Due to the fact that sharding has the capability of solving this problem, the scalability of the network can be increased. One of the significant challenges in this study was determining how sharding would affect the...

Current Internet of Things (IoT) infrastructures rely on cloud storage however, relying on a single cloud provider puts limitations on the IoT applications and Service Level Agreement (SLA) requirements. Recently, multiple decentralized storage solutions (e.g., based on blockchains) have entered the market with distinct architecture, Quality of Ser...

In industrial sectors, the supply chain management (SCM) systems have been getting smarter by accepting and deploying of evolutionarily advanced technologies, for example, the Internet of Things (IoT). IoT made a supply chain more efficient than ever before; IoT analytical tools enable the organizations to manage and react to all important issues a...

The Intelligent Transportation System (ITS) has become essential for the economical and technological development of a country. The maturity of communication technologies (Vehicle to Infrastructure (V2I) and Vehicle to Vehicle (V2V)) and the amalgamation of smart grids, electric vehicles (EVs) and energy trading resulted in a storm of research oppo...

Sharding has emerged as one of the common techniques to address the scalability problems of blockchain systems. To this end, various sharding techniques for blockchain systems have been proposed in the literature. When sharded blockchains process personal data, the data controllers and the data processors associated with the sharded blockchains nee...

LoRaWAN, part of the long range Internet of Things (IoT) technologies, is a Low Power Wide Area (LPWA) protocol that enables communication between the battery operated resource constrained devices. Although LoRaWAN provides system-level security, these networks are based on a basic assumption of trust between the network server and the user, which...

Undoubtedly, the supply chain management (SCM) system is an important part of many organizations worldwide; over time, the technologies used to manage a supply chain ecosystem have, therefore, a great impact on businesses’ effectiveness. Among others, numerous developments have been made that targeted to have robust supply chain systems to efficien...

With the emergence of new smart technologies, including the Internet of Things, wireless media are playing an important role to connect numerous devices to fulfill the requirements of newly developed communication systems. The massive connectivity, therefore, made the wireless spectrum too crowded and gave several challenges to resisting against po...

Current Internet of Things (IoT) infrastructures, with its massive data requirements, rely on cloud storage: however, usage of a single cloud storage can place limitations on the IoT applications in terms of service requirements (performance, availability, security etc.). Multi-cloud storage architecture has emerged as a promising infrastructure to...

Many IoT applications found in cyber-physical systems, such as smart grids, must take control actions in response to critical events, such as supply-demand mismatch, which requires low-latency processing of streaming data for rapid event detection and anomaly remediation. These streaming applications generally take the form of directed acyclic grap...

Blockchain networks which employ Proof-of-Work in their consensus mechanism may face inconsistencies in the form of forks. These forks are usually resolved through the application of block selection rules (such as the Nakamoto consensus). In this paper, we investigate the cause and length of forks for the Bitcoin network. We develop theoretical for...

Firewalls are located at the front line of the network against outside threats. Performance modelling and analysis of network firewalls helps to better understand their behavior and characteristics. As well, having an analytical model in hand helps firewall designers avoid developing multiple design alternatives and thus considerably reduce the des...

Blockchains are currently gaining attention as a newly emerging technology in both academia and industry, capable of impacting a variety of domains beyond cryptocurrencies. Performance modeling can be used to provide us with a deeper understanding of the behavior and dynamics within blockchain peer-to-peer networks. Blockchain system architects can...

The success and growing popularity of blockchain technology has lead to a significant increase in load on popular permissionless blockchains such as Ethereum. With the current design, these blockchain systems do not scale with additional nodes since every node executes every transaction. Further efforts are therefore necessary to develop scalable p...

Known for powering cryptocurrencies such as Bitcoin and Ethereum, blockchain is seen as a disruptive technology capable of revolutionizing a wide variety of domains, ranging from finance to governance, by offering superior security, reliability, and transparency founded upon a decentralized and democratic computational model. In this tutorial, we f...

Popularly known for powering cryptocurrencies such as Bitcoin and Ethereum, blockchains is seen as a disruptive technology capable of impacting a wide variety of domains, ranging from finance to governance, by offering superior security, reliability, and transparency in a decentralized manner. In this tutorial presentation, we first study the origi...

The recent success of electric vehicles leads to unprecedentedly high peaks of demand on the electric grid at the times when most people charge their cars. In order to avoid unreasonably rising costs due to inefficient utilization of the electricity infrastructure, we propose EVA: a scheduling system to solve the valley filling problem by distribut...

We investigate the use of content-based publish/subscribe for data dissemination in large-scale applications with expressive filtering requirements. In particular, we focus on top-k subscription filtering, where a publication is delivered only to the k best ranked subscribers, as ordered using expressive semantics such as relevance, fairness, and d...

Since the introduction of Bitcoin in 2008, blockchain systems have evolved immensely in terms of performance and usability. There is a massive focus on building enterprise blockchain solutions, with providers such as IBM and Microsoft already providing Blockchain-as-a Service (BaaS). To facilitate the adoption of blockchain technologies across vari...

Massively multiplayer online role-playing games (MMORPGs) allow thousands of players to interact with each other in a large-scale virtual environment. Interest management is an important technique used to raise the scalability of a game by limiting the amount of information transmitted to the players according to their relevance. In this paper, we...

Following the success of Bitcoin, Ethereum and Hyperledger, blockchains are now gaining widespread adoption in a wide variety of applications, using a diversity of distributed ledger systems with varying characteristics. Yet, beyond the original bitcoin protocol, the safety and reliability properties of such systems are not sufficiently analyzed. T...

Distributed content-based publish/subscribe systems provide a selective, scalable, and decentralized approach to data dissemination. In a pub/sub overlay network, hop-by-hop routing allows brokers to correctly forward messages without requiring global knowledge. However, this model causes brokers to forward publications without knowing the volume a...

Shared dictionary compression is known as an efficient compression method for pub/sub. In practice, bandwidth reductions of more than 80% are achievable for JSON or XML data formats. Compared to other compression techniques such as GZip or Deate, a dictionary is needed to compress and decompress messages. Generating a dictionary is a CPU-expensive...

Publish/subscribe is known as a scalable and efficient data dissemination mechanism. Its efficiency comes from the optimized routing algorithms, yet few works exist on employing compression to save bandwidth, which is especially important in mobile environments. State of the art compression methods such as GZip or Deflate can be generally employed...

We identify a class of content-based pub/sub applications with highly dynamic subscriptions. This includes location-based notification systems, predictive stock trading, and multiplayer games. The traditional method of handling subscription changes by engaging in expensive re-subscription protocols is inadequate when the workload is sufficiently la...

Traffic monitoring is an important stream processing application, which is highly dynamic and requires aggregation of spatially collocated data. Inspired by this, the DEBS 2015 Grand Challenge uses publicly available taxi transportation information to compute online the most frequent routes and most profitable areas. We describe our solution to the...

Massively multiplayer online games (MMOGs), which are typically supported by large distributed systems, require a scalable, low latency messaging middleware that supports the location-based semantics and the loosely coupled interaction of multiplayer games components. In this paper, we present three different pub/sub-driven designs for a MMOG netwo...

The publish/subscribe paradigm has found wide acceptance in a broad variety of use cases that differ dramatically in the characteristics of their workloads. Many different systems have been developed both by academia as well as industry, but there is no definitive benchmark, which enables a fair comparison between the different systems. In this dem...

Massively multiplayer online games have to handle huge amounts of load caused by thousands of concurrent players and require a scalable, low-latency middleware system for their messaging needs. In this demonstration we will showcase the three pub/sub network designs that we developed for our Middleware 2014 paper titled "Publish/Subscribe Network D...

Content-Centric Networking (CCN) is a proposed model for Future Internet Architecture (FIA) which replaces traditional host-oriented interactions with named data networking. In this demo, we present PSoCCN, our model for supporting a software-level publish/subscribe middleware over CCN. Our model demonstrates how CCN features can be leveraged to su...

Modern data-intensive applications handling massive event streams such as real-time traffic monitoring require support for both rich data filtering and aggregation. While the pub/sub communication paradigm provides an effective solution for the sought semantic diversity of event filtering, the event processing capabilities of existing pub/sub syste...

Real-time traffic analysis is an interesting research topic across different disciplines and areas. In order to provide a better and practical way of representing and gathering traffic data, we need to have a suitable media with high mobility and qualitative performance such as smartphones. This paper proposes a smartphone application which present...

Software-Defined Networking (SDN) has raised the boundaries of cloud computing by offering unparalleled levels of control and flexibility to system administrators over their virtualized environments. To properly embrace this new era of SDN-driven network architectures, the research community must not only consider the impact of SDN over the protoco...

The amount of content served on social networks can overwhelm users, who must sift through the data for relevant information. To facilitate users, we develop and implement dissemination of ranked data in social networks. Although top-k computation can be performed centrally at the user, the size of the event stream can constitute a significant bott...

Application performance monitoring (APM) is shifting towards capturing and analyzing every event that arises in an enterprise infrastructure. Current APM systems, for example, make it possible to monitor enterprise applications at the granularity of tracing each method invocation (i.e., an event). Naturally, there is great interest in monitoring th...

This paper presents the design and implementation of a custom-built event processing engine called BlueBay developed for live monitoring of soccer games. We experimentally evaluated our system using a real workload and report on its performance. Our results indicate that BlueBay achieves a throughput of up to 790k events per second, therefore proce...

The publish/subscribe paradigm is known for its loosely coupled interactions and event filtering capabilities. Traditional applications using pub/sub systems require large-scale deployment and high event throughput. Thus, pub/sub has always put the emphasis on scalability and performance, to the detriment of filtering expressiveness and quality of...

In this paper, we present an efficient complex event processing system tailored toward monitoring a large-scale setup of manufacturing equipment. In particular, the key challenge in the equipment monitoring is to develop an event-based system for computing complex manufacturing queries coupled with event notifications and event and query result vis...

Total ordering is a messaging guarantee increasingly required of content-based pub/sub systems, which are traditionally focused on performance. The main challenge is the uniform ordering of streams of publications from multiple publishers within an overlay broker network to be delivered to multiple subscribers. Our solution integrates total orderin...