On Trees, Chains and Fast Transactions in the Blockchain

A fundamental open problem in the area of blockchain protocols is whether the Bitcoin protocol is the only solution for building a secure transaction ledger. A recently proposed and widely considered alternative is the \GHOST protocol which, notably, was proposed to be at the core of Ethereum as well as other recent proposals for improved Bitcoin-like systems. % The \GHOST variant is touted as offering superior performance compared to Bitcoin (potentially offering block production speed up by a factor of more than 40) without a security loss. Motivated by this, in this work, we study from a provable security point of view the \GHOST protocol. We introduce a new formal framework for the analysis of blockchain protocols that relies on trees (rather than chains) and we showcase the power of the framework by providing a unified description of the \GHOST and Bitcoin protocols, the former of which we extract and formally describe. We then prove that \GHOST implements a ``robust transaction ledger\u27\u27 (i.e., possesses liveness and persistence) and hence it is a provably secure alternative to Bitcoin; moreover, our bound for the liveness parameter is superior to that proven for the bitcoin backbone in line with the original expectation for \GHOST. Our proof follows a novel methodology for establishing that \GHOST is a robust transaction ledger compared to previous works, which may be of independent interest and can be applicable to other blockchain variants

Blockchain Challenges and Security Schemes: A Survey

International audienceWith the increasing number of connected devices and the number of online transactions today, managing all these transactions and devices and maintaining network security is a research issue. Current solutions are mainly based on cloud computing infrastructures, which require servers high-end and broadband networks to provide data storage and computing services. These solutions have a number of significant disadvantages, such as high maintenance costs of centralized servers, critical weakness of Internet Of Things applications, security and trust issues, etc. The blockchain is seen as a promising technique for addressing the mentioned security issues and design new decentralization frameworks. However, this new technology has a great potential in the most diverse technological fields. In this paper, we focus on presenting an overview of blockchain technology, highlighting its advantages, limitations and areas of application. The originality of this work resides in the comparison between the different blockchain systems and their security schemes and the perspective of integrating this technology into secured systems models for our comfort and our private life

Blockchain Technology, Technical Challenges and Countermeasures for Illegal Data Insertion

Blockchain is a decentralized transaction and data management technology. It was developed for the world’s first cryptocurrency known as Bitcoin in 2008. The reason behind its popularity was its properties which provide pseudonymity, security, and data integrity without third-party intervention.  Initially, most of the researches were focused on the Bitcoin system and its limitation, but later other applications of Blockchain e.g. smart contracts and licensing [1] also got famous. Blockchain technology has the potential to change the way how transactions are conducted in daily life. It is not limited to cryptocurrencies but could be possibly applied in various environments where any forms of transactions are done. This article presents a comprehensive overview of Blockchain technology, its development, applications, security issues, and their countermeasures. In particular, the security towards illegal data insertion and the countermeasures is focused. Our analysis of countermeasures of illegal data insertion can be combined for increased efficiency. After the introduction of the Blockchain and consensus algorithm, some famous Blockchain applications and expected future of Blockchain are deliberated. Then, the technical challenges of Blockchain are discussed, in which the main focus here is on the security and the data insertion in Blockchain. The review of the possible countermeasures to overcome the security issues related to data insertion are elaborated

Simulation of stochastic blockchain models

International audienceThis paper build the foundations of a simulation tool for blockchain-based applications. It takes advantage of the huge expressiveness and extensibility of PyCATSHOO framework to deal with the important variability of blockchain implementations and properties of interest. A simple stochastic model of generic blockchain-style distributed consensus system and associated performance indicators are proposed (performance in terms of consistency and ability to discard double-spending attacks). Monte Carlo simulations are applied to assess the indicators and determine their sensitivity to the variation of input parameters

Low-resource eclipse attacks on Ethereum’s peer-to-peer network

We present eclipse attacks on Ethereum nodes that exploit the peer-to-peer network used for neighbor discovery. Our attacks can be launched using only two hosts, each with a single IP address. Our eclipse attacker monopolizes all of the victim’s incoming and outgoing connections, thus isolating the victim from the rest of its peers in the network. The attacker can then filter the victim’s view of the blockchain, or co-opt the victim’s computing power as part of more sophisticated attacks. We argue that these eclipse-attack vulnerabilities result from Ethereum’s adoption of the Kademlia peer-to-peer protocol, and present countermeasures that both harden the network against eclipse attacks and cause it to behave differently from the traditional Kademlia protocol. Several of our countermeasures have been incorporated in the Ethereum geth 1.8 client released on February 14, 2018.First author draf

Blockchain for next generation services in banking and finance: cost, benefit, risk and opportunity analysis

YesPurpose – The purpose of this paper is to help in providing a better understanding of the application of blockchain technology in the context of the banking and finance sectors. The aim is to outline blockchain’s benefits, opportunities, costs, risks as well as challenges of the technology in the context of banking and finance services Design/methodology/approach – Careful examination of the extant literature, including utilising relevant academic-based research databases has been carried out. It covered reviewing various research contributions published in peer-reviewed journals, academic reports, as well as technical reports to help in identifying related benefits, opportunities, costs, and risks. Findings – The findings reveal that there are limited contributions in utilising blockchain in the banking and finance sectors when compared with other sectors. As such, the study highlighted the relevant perspective of benefits, opportunities, costs, and risks within such sectors. Practical implications – This study helps in offering a focal point to banking and financial sector managers and decision-makers for realising the benefits of blockchain technology as well as developing strategies and programmes to overcome the identified challenges. Originality/value – This study highlights the need for a holistic understanding of the various aspects of cost, benefits, risk and opportunities to create blockchain applications that work for banking and finance sectorsNPRP grant # [11S-0117–180325] from the Qatar National Research Fund (a member of Qatar Foundation)

DAGsim: Simulation of DAG-based distributed ledger protocols

Scalability of distributed ledgers is a key adoption factor. As an alternative to blockchain-based protocols, directed acyclic graph (DAG) protocols are proposed with the intention to allow a higher volume of transactions to be processed. However, there is still limited understanding of the behaviour and security considerations of DAG-based systems. We present an asynchronous, continuous time, and multi-agent simulation framework for DAG-based cryptocurrencies. We model honest and semi-honest actors in the system to analyse the behaviour of one specific cryptocurrency, IOTA. Our simulations show that the agents that have low latency and a high connection degree have a higher probability of having their transactions accepted in the network with honest and semi-honest strategies. Last, the simulator is built with extensibility in mind. We are in the process of implementing SPECTRE as well as including malicious agents