Formal Modeling and Verification of a Blockchain-Based Crowdsourcing Consensus Protocol

Crowdsourcing is an effective technique that allows humans to solve complex problems that are hard to accomplish by automated tools. Some significant challenges in crowdsourcing systems include avoiding security attacks, effective trust management, and ensuring the system’s correctness. Blockchain is a promising technology that can be efficiently exploited to address security and trust issues. The consensus protocol is a core component of a blockchain network through which all the blockchain peers achieve an agreement about the state of the distributed ledger. Therefore, its security, trustworthiness, and correctness have vital importance. This work proposes a Secure and Trustworthy Blockchain-based Crowdsourcing (STBC) consensus protocol to address these challenges. Model checking is an effective and automatic technique based on formal methods that is utilized to ensure the correctness of STBC consensus protocol. The proposed consensus protocol’s formal specification is described using Communicating Sequential Programs (CSP#). Safety, fault tolerance, leader trust, and validators’ trust are important properties for a consensus protocol, which are formally specified through Linear Temporal Logic (LTL) to prevent several security attacks, such as blockchain fork, selfish mining, and invalid block insertion. Process Analysis Toolkit (PAT) is utilized for the formal verification of the proposed consensus protocol

A Blockchain Simulator for Evaluating Consensus Algorithms in Diverse Networking Environments

The massive scale, heterogeneity and distributed nature of Internet-of-Things (IoT) presents challenges in realizing a practical and effective security solution. Blockchain empowered platforms and technologies have been proposed to address aspects of this challenge. In order to realize a practical Blockchain deployment for IoT, there is a need for a testing and evaluation platform to evaluate performance and security of Blockchain applications and systems. In this paper, we present a Blockchain simulator that evaluates the consensus algorithms in a realistic and configurable network environment. Though, there are several Blockchain evaluation platforms, they are either wedded to a specific consensus protocol and do not allow evaluation in a configurable and realistic network environment. In our proposed simulator, we provide the ability to evaluate the impact of the consensus and network layer that will inform practitioners on the appropriate choice of consensus algorithms and the impact of network layer events in congested or contested scenarios in IoT. To accomplish this a generalized representation for consensus methods is proposed. The Blockchain simulator uses a discrete event simulation engine for fidelity and increased scalability. We evaluate the performance of the simulator by varying the number of peer nodes and number of messages required to find consensus

Measuring Decentrality in Blockchain Based Systems

Blockchain promises to provide a distributed and decentralized means of trust among untrusted users. However, in recent years, a shift from decentrality to centrality has been observed in the most accepted Blockchain system, i.e., Bitcoin. This shift has motivated researchers to identify the cause of decentrality, quantify decentrality and analyze the impact of decentrality. In this work, we take a holistic approach to identify and quantify decentrality in Blockchain based systems. First, we identify the emergence of centrality in three layers of Blockchain based systems, namely governance layer, network layer and storage layer. Then, we quantify decentrality in these layers using various metrics. At the governance layer, we measure decentrality in terms of fairness, entropy, Gini coefficient, Kullback-Leibler divergence, etc. Similarly, in the network layer, we measure decentrality by using degree centrality, betweenness centrality and closeness centrality. At the storage layer, we apply a distribution index to define centrality. Subsequently, we evaluate the decentrality in Bitcoin and Ethereum networks and discuss our observations. We noticed that, with time, both Bitcoin and Ethereum networks tend to behave like centralized systems where a few nodes govern the whole network

A method of developing an agent based ubiquitous node monitoring protocol

A ubiquitous network plays a critical role to provide rendered services to ubiquitous application running nodes. To provide appropriate resources the nodes are needed to be monitored continuously. Monitoring a node in ubiquitous network is challenging because of dynamicity and heterogeneity of the ubiquitous network. The network monitor has to monitor resource parameters, like data rate, delay and throughput, as well as events such as node failure, network failure and fault in the system to curb the system failure. In this paper, we propose a method to develop a ubiquitous system monitoring protocol using agents. Earlier works on network monitoring using agents consider that the agents are designed for particular network. While in our work the heterogeneity property of the network has been considered. We have shown that the nodes' behaviour can be easily monitored by using agents (both static and mobile agent). The past behavior of the application and network, and past history of the Unode and the predecessor are taken into consideration to help SA to take appropriate decision during the time of emergency situation like unavailability of resources at the local administration, and to predict the migration of the Unode based on the previous node history. The results obtained in the simulation reflects the effectiveness of the technique

Performance Analysis of a Priority based Resource Allocation Scheme in Ubiquitous Networks

Abstract It is difficult to perform resource allocation for a node with the agreed QoS requirement in a ubiquitous network, which consists of subnetwork segments of different technologies with different resource constraints and control. In this paper, we discuss performance analysis of a priority based resource allocation scheme for the Unodes, i.e., nodes running a ubiquitous application in a ubiquitous network. The proposed protocol exploits the advantages of both Static and Mobile Agents, by deploying them in different subnetworks (as and when required) to help the local administration to provide required network resources to the Unodes, and to ensure that the Unodes get the required network resources-by continuously monitoring their resource utilization and taking proactive actions. Mobile Agents (MAs) calculate the priorities of Unodes-by considering the importance of the application running on them, their resource utilization history and the cost effectiveness of the resource-and use those to allocate network resources among the contending Unodes fairly. We have built an analytical model of the proposed resource allocation scheme using queuing concept. The results obtained in the simulation and analysis reflects the effectiveness of the proposed scheme

An efficient way of providing information in ubiquitous tourist system

A ubiquitous tourist system provides information and services available at tourist spots to the tourists unobtrusively. The information need to be provided in personalized way suitable to tourists with different requirements. To enable such efficient way of information provision, we need to consider the QoS requirements of the application and maintain it with the changing context of the tourist by monitoring the network and information usage. Predicting and maintaining QoS for the ubiquitous tourist system is very difficult as the user is highly mobile in a ubiquitous network, as the resources requirement of the system changes continuously. Similarly, monitoring the devices used by the tourist is also challenging because of the dynamically changing user's position in the ubiquitous network consisting of several heterogeneous subnetworks. Hence, there is a need to ensure QoS maintenance and monitoring the resource utilization to provide the tourist exhibit information in an efficient way. In this paper, we discuss about an efficient way to provide information to the tourists by considering the context of the user, the profile information, the types of services user needs, and the history information. The system predicts the QoS requirements of the different tourist devices, and provides the network resources in different subnetworks by sending mobile agents to negotiate with the local administrators. The ubiquitous system is fully aware of user's knowledge level, network conditions, interests, daily routine, etc. So, it plans accordingly to provide required service without interruption. The designed system is tested by simulation with different scenarios and showed the efficiency of our model

Distributed Active Learning Strategies on Edge Computing

Publication in Conference proceedings/Worksho