Blockchain Papers

Joshua S. Gans

No abstract is available for this record.

Joshua S. Gans

No abstract is available for this record.

Joshua Ellul, Gordon J. Pace

No abstract is available for this record.

Siamak Solat

Cette thèse de doctorat se compose de 6 chapitres. Dans le premier chapitre, en guise d'introduction, nous donnons un aperçu des objectifs généraux et des motivations des réseaux décentralisés et permissionless, ainsi que des obstacles auxquels ils sont confrontés. Dans l'introduction, nous évoquons également la solution irrationnelle et illogique, connue sous le nom de « blockchain permissioned », qui a été proposée pour améliorer les performances des réseaux similaires à Bitcoin. Cette question a été détaillée au chapitre 5. Dans le chapitre 2, nous rendons clairs et intelligibles les systèmes que l'idée proposée, « Parallel Committees », est basée sur de tels réseaux. Nous détaillons les fonctionnalités indispensables et les défis essentiels des systèmes de réplication. Ensuite, dans le chapitre 3, nous discutons des limitations de scalabilité et du faible débit des systèmes de réplication qui utilisent des mécanismes de consensus pour traiter les transactions et comment ces problèmes peuvent être améliorés en utilisant des techniques de sharding. Nous décrivons les défis les plus importants dans le sharding des systèmes de réplication distribuée, une approche qui a déjà été mise en œuvre dans plusieurs systèmes de réplication basés sur la blockchain et, bien qu'elle ait montré un potentiel significatif pour améliorer les performances et la scalabilité, les techniques de sharding actuelles ont encore des limitations de scalabilité et des défis de sécurité. Nous expliquons pourquoi la plupart des protocoles de sharding actuels utilisent une approche d'allocation aléatoire pour distribuer les nœuds entre les shards pour des raisons de sécurité. Nous décrivons également comment traiter une transaction dans un système de réplication partitionné basé sur les protocoles de sharding actuels. Nous expliquons comment un « shared-ledger » partagé sur les shards impose des limitations de scalabilité et des défis de sécurité au réseau, et expliquons pourquoi les transactions « cross-shards » ou « inter-shards » sont indésirables et plus coûteuses en raison des problèmes qu'elles causent, y compris « atomicity failure » et les défis de « state transition », ainsi qu'une passe en revue des solutions proposées. Nous passons également en revue certains des travaux récents les plus remarquables qui utilisent des techniques de sharding pour les systèmes de réplication. Cette partie de l'ouvrage a été publiée sous la forme d'un chapitre de livre (peer-reviewed) in « Building Cybersecurity Applications with Blockchain Technology and Smart Contracts » (Springer, 2023). Dans le chapitre 4, nous proposons une nouvelle technique de sharding, « Parallel Committees », prenant en charge à la fois le « processing-sharding » et le « storage/state sharding », pour améliorer la scalabilité et les performances des systèmes de réplication distribués qui utilisent des mécanismes de consensus pour traiter les demandes des clients (client requests). Nous introduisons une approche innovante et originale pour répartir les nœuds entre les shards à l'aide d'un processus de génération de clé publique qui atténue simultanément l'attaque Sybil et sert de mécanisme de preuve de travail (proof-of-work). Notre approche réduit efficacement les transactions « inter-shards » indésirables, qui sont plus complexes et coûteuses à traiter que les transactions « intra-shards ». L'idée proposée a été publiée dans la conférence IEEE BCCA 2023. Nous expliquons ensuite pourquoi nous n'utilisons pas la structure de la blockchain dans l'idée proposée, un sujet abordé en détail au chapitre 5. Cette explication et clarification a été publiée dans le Journal of Software (JSW), Volume 16, Number 3, May 2021. Et dans le dernier chapitre de cette thèse, le chapitre 6, nous résumons les points importants et les conclusions de cette recherche.

Fredrik Kamphuis, Bernardo Magri, Ricky Lamberty, Sebastian Faust

No abstract is available for this record.

David R. Surma

This thesis deals with the analysis of the blockchain used for Bitcoin. Blockchain is a distributed database of all transactions made with this cryptocurrency. Its public availability represents the possibility of examining the transfer of funds between all users. However, they appear in transactions under anonymous addresses, the number of which is practically unlimited. The main goal of our work is to find a clustering of addresses corresponding to their belonging to real users. In this work, we propose new heuristics that can be used in clustering. The main benefit is a method that uses the properties of transactions created very quickly one after the other. Furthermore, we analyze the problem of the formation of a supercluster containing a disproportionately large number of addresses and propose a way in which the cluster can be appropriately partitioned. 1

Manaswini Piduguralla, Saheli Chakraborty, Parwat Singh Anjana, Sathya Peri

No abstract is available for this record.

Elvira Albert, Samir Genaim, Daniel Kirchner, Enrique Martin-Martin

Abstract The efficiency and the security of smart contracts are their two fundamental properties, but might come at odds: the use of optimizers to enhance efficiency may introduce bugs and compromise security. Our focus is on (Ethereum Virtual Machine) block-optimizations , which enhance the efficiency of jump-free blocks of opcodes by eliminating, reordering and even changing the original opcodes. We reconcile efficiency and security by providing the verification technology to formally prove the correctness of block-optimizations on smart contracts using the Coq proof assistant. This amounts to the challenging problem of proving semantic equivalence of two blocks of instructions, which is realized by means of three novel Coq components: a symbolic execution engine which can execute an block and produce a symbolic state; a number of simplification lemmas which transform a symbolic state into an equivalent one; and a checker of symbolic states to compare the symbolic states produced for the two blocks under comparison. Artifact: https://doi.org/10.5281/zenodo.7863483

Sara Barj, Aafaf Ouaddah, Abdellatif Mezrioui

No abstract is available for this record.

Nishanth Uchil

Demand for blockchain ecosystems has seen exponential growth in recent times due to its decentralized nature and trustless verification process for the transactions involved. However, transaction data needs to be leveraged for verification, which coupled with the transparent nature of the blockchain ledger, provides sufficient data for malicious entities to reveal identities and even financial history of users. Data masking techniques have been employed over the years to make blockchain transactions anonymous, making them resistant to identity analysis, a key set of methods being zero-knowledge proof (zk-proof) protocols that guarantee zero data leak. In this research, we develop SpartanDark, a fork of SpartanGold that integrates a zk-proof protocol, Zero-Knowledge Succinct Non-interactive Argument of Knowledge (zk-SNARK) for transaction verification. SpartanDark provides a Decentralized Anonymous Payment scheme (DAP) with anonymity guarantees, akin to the privacy transaction model in Zerocash. Our analysis shows that this transaction model presents a high degree of data privacy when compared to traditional blockchain models, carrying zero identifying information about the transaction across the blockchain, making it implausible for other entities to profile any user and thus reestablishing one of the core tenets of blockchain: privacy.

Leonardo Mostarda, Andrea Pinna, Davide Sestili, Roberto Tonelli

No abstract is available for this record.

Babu Pillai, Zhé Hóu, Kamanashis Biswas, Vallipuram Muthukkumarasamy

This paper introduces an abstract blockchain model that employs the Burn-to-Claim cross-blockchain protocol [1]. This multi-level simulator models a virtual environment of nodes running on the Ethereum Virtual Machine (EVM). Developed using the $$CSP\#$$ language [2], it has undergone formal verification with the model checker PAT. Focusing on inter-network operations, our model ( https://github.com/b-pillai/Burn-to-Claim-formal-verification ) examines the properties of correctness, security, and atomicity using PAT. Surprisingly, atomicity, assumed to be inherent in the time-lock mechanism of the Burn-to-Claim protocol, does not always hold. We establish its validity under specific assumptions while confirming the protocol’s correctness and security under the added assumptions.

Carlos Álvarez López, Yeray Mezquita, Diego Valdeolmillos

No abstract is available for this record.

Ivaylo Chenchev

No abstract is available for this record.

Anas Alsobeh, Aws A. Magableh

Blockchain systems are lauded for their security and reliability. Security is a cornerstone, as they employ cryptographic techniques to ensure the immutability of data, making it extremely resistant to tampering. With decentralized networks, they also reduce the risk of a single point of failure, enhancing reliability. Model checking plays a vital role in ensuring the security and reliability of blockchain systems. However, traditional model-checking approaches face challenges in handling the inherent dynamism exhibited in blockchain systems. To overcome this challenge, Aspect-Oriented programming (AOP) offers capabilities to enhance blockchain model checking through the modularization of cross-cutting concerns, enabling traceability and monitoring, facilitating dynamic instrumentation, and supporting fine-grained property specifications. The aim of this research is to enable more effective and efficient verification of dynamic behaviors in blockchain systems compared to conventional model-checking techniques using AOP. As a result, this research introducesBlockASP, a novel blockchain model verification method that leverages AOP to analyze and monitor dynamic behavior of the blockchain system.BlockASPintegrates the benefits of aspect-orientation and model checking into the blockchain architecture to strengthen security and reliability. This research has examined prior arts that are related to blockchain modeling using Object-oriented (OO) and those that are using AOP. Our research has proposed and discussed theBlockASPtechnique, the research provided a case study to demonstrate the validity and superiority in facilitating the monitoring of dynamic blockchain behavior using AOP compared to traditional approaches such as Model-Driven Architecture (MDA).

Carlos Núñez‐Gómez, Martijn de Vos, Jérémie Decouchant, Johan Pouwelse · 6 authors

With the proliferation of Internet of Things (IoT) ecosystems, traditional resource orchestration mechanisms, executed on fog devices, encounter significant scalability, reliability and security challenges. To tackle these challenges, recent decentralized algorithms in Fog-IoT use Distributed Ledger Technologies to orchestrate resources and payments between peers. However, while distributed ledgers provide many desirable properties, their consensus mechanism introduces a performance bottleneck. This paper introduces Light-HIDRA, a consensus-less and decentralized resource orchestration system for Fog-IoT environments. At its core, Light-HIDRA uses Byzantine Reliable Broadcast (BRB) to coordinate actions without centralized control, therefore drastically reducing communication overhead and latency compared to consensus-based solutions. Light-HIDRA coordinates the scheduling and execution of workloads, and securely manages the payments that peers receive for dedicating resources to workloads. Light-HIDRA further increases performance and reduces overhead by grouping peers into distinct domains. We conduct an in-depth analysis of the protocol’s security properties, investigating its efficiency and robustness in diverse situations. We evaluate the performance of Light-HIDRA, highlighting its performance over HIDRA, a state-of-the-art baseline that uses smart contracts. Our experiments demonstrate that Light-HIDRA reduces the bandwidth usage by up to 57x, the latency of workload offloading by up to 142x, and shows superior throughput compared to HIDRA.

Alex Kemloh Kouyem

Diese Arbeit präsentiert ein Protokoll für vertrauliche Transaktionen auf Ethereum, das auf einer kontenbasierten Struktur und Paillier-Verschlüsselung basiert. Die Integration von Non-Interactive Zero-Knowledge Range Proofs (NIZKRP) verbessert die Sicherheit. Die Implementierung und Tests auf Ethereum zeigen vergleichbare Transaktionskosten (Sicherheitsparameter 40) im Vergleich zu Protokollen mit Bulletproofs. Bei einem Sicherheitsparameter von 128 (NIZKRP-Empfehlung) ist das Protokoll jedoch nicht anwendbar. Die Arbeit betont die Effizienz und Wettbewerbsfähigkeit, hebt jedoch die Herausforderung bei höheren Sicherheitsparametern hervor. Das Protokoll bildet eine solide Grundlage, erfordert jedoch weitere Optimierungen für breitere Anwendbarkeit.

Bertalan Zoltán Péter, Imre Kocsis

In this paper, we propose the application of a well-known runtime fault-tolerance technique, N-Version Program-ming (NVP), as a new tool of smart contract software fault mitigation, especially for execute-order-validate blockchain systems, such as Hyperledger Fabric (HLF). Two patterns for aligning the NVP concept with the HLF architecture are proposed. A fully transparent solution where all peers have the same N versions installed and one we termed ‘O-Version Programming’ (where ‘O’ stands for ‘Organization’), which relies on the majority voting aspects of execute-order-validate consensus mechanisms.

Ramesh Adhikari, Costas Busch

Sharding is used to address the performance and scalability issues of the blockchain protocols, which divides the overall transaction processing costs among multiple clusters of nodes. Shards require less storage capacity and communication and computation cost per node than the existing whole blockchain networks, and they operate in parallel to maximize performance. However, existing sharding solutions use locks for transaction isolation which lowers the system throughput and may introduce deadlocks. In this paper, we propose a lockless transaction method for ensuring transaction isolation without using locks, which improves the concurrency and throughput of the transactions. In our method, transactions are split into subtransactions to enable parallel processing in multiple shards. We use versions for the transaction accounts to implement consistency among the shards. We provide formal proof for liveness and correctness. We also evaluate experimentally our proposed protocol and compare the execution time and throughput with lock-based approaches. The experiments show that the transaction execution time is considerably shorter than the lock-based time and near to the ideal (no-lock) execution time.

Ehud Shapiro

Informally, a distributed system is grassroots if it is permissionless and can have autonomous, independently-deployed instances - geographically and over time - that may interoperate voluntarily once interconnected. More formally, in a grassroots system the set of all correct behaviors of a set of agents P is strictly included in the set of the correct behaviors of P when they are embedded within a larger set of agents P' ⊃ P. Grassroots systems are potentially important as they may allow communities to conduct their social, economic, civic, and political lives in the digital realm solely using their members' networked computing devices (e.g., smartphones), free of third-party control, surveillance, manipulation, coercion, or rent seeking (e.g., by global digital platforms such as Facebook or Bitcoin). Client-server/cloud computing systems are not grassroots, and neither are systems designed to have a single global instance (Bitcoin/Ethereum with hardwired seed miners/bootnodes), and systems that rely on a single global data structure (IPFS, DHTs). An example grassroots system would be a serverless smartphone-based social network supporting multiple independently-budding communities that can merge when a member of one community becomes also a member of another. Here, we formalize the notion of grassroots distributed systems; describe a grassroots dissemination protocol for the model of asynchrony and argue its safety, liveness, and being grassroots; extend the implementation to mobile (address-changing) devices that communicate via an unreliable network (e.g. smartphones using UDP); and discuss how grassroots dissemination can realize grassroots social networking and grassroots cryptocurrencies. The mathematical construction employs distributed multiagent transition systems to define the notions of grassroots protocols, to specify the grassroots dissemination protocols, and to prove their correctness. The protocols use the blocklace - a distributed, partially-ordered counterpart of the replicated, totally-ordered blockchain.

Zeta Avarikioti, Antoine Desjardins, Lefteris Kokoris-Kogias, Roger Wattenhofer

No abstract is available for this record.

John Stuart

Avec la montée en puissance des ordinateurs quantiques, il est plus important que jamais de démontrer que les protocoles cryptographiques sont sécuritaires contre des adversaires quantiques. De plus, l'objectif de tout cryptographe est d’assouplir certaines hypothèses, en particulier celles qui restreignent la capacité de l’adversaire à effectuer de longs calculs. Dans cette thèse, un système multi-parties est utilisé pour créer deux preuves Zéro-Knowledge (ZK), celles-ci opèrent en temps polynomial et sont sécurisées. De plus, elles n’ont aucune restriction calculatoire pour aucune partie, même pour les adversaires qui partagent une intrication quantique. Une preuve ZK permet à une partie de prouver à une autre partie d’un fait sans révéler aucune connaissance autre que la véracité du fait. Par exemple, une telle preuve pourrait être utilisée pour permettre à un client de prouver son identité à un guichet bancaire sans donner des renseignements confidentiels tel que son numéro d'identification personnel. Un des principaux outils utilisés lors d’une preuve ZK est le schéma de mise en gage. Celui-ci est essentiellement un outil numérique permettant à un expéditeur de sceller un message dans un coffre-fort et de l’envoyer à un destinataire. Ensuite, quand l'expéditeur veut que le destinataire lise le message, la clé du coffre fort lui est envoyée. Ceci permet au message de rester inconnu du receveur jusqu'à ce qu’il reçoive la clé de l'expéditeur. De plus, l'expéditeur ne peut pas changer le message une fois le coffre-fort envoyé. Au cours de cette thèse, les propriétés homomorphiques d’un schéma multi-parties de mise en gage sont utilisées pour permettre au destinataire d’effectuer des opérations sur le gage. Ceci donne ainsi des preuves ZK pour deux problèmes NP-complets, les problèmes de la somme de sous-ensembles et 3-SAT

Sangita Roy, R. K. Shyamasundar

No abstract is available for this record.

Ray Neiheiser, Gustavo Inácio, Luciana Rech, Carlos Montez · 6 authors

Most permissionless blockchains inherently suffer from throughput limitations. Layer-2 systems, such as side-chains or Rollups, have been proposed as a possible strategy to overcome this limitation. Layer-2 systems interact with the main-chain in two ways. First, users can move funds from/to the main-chain to/from the layer-2. Second, layer-2 systems periodically synchronize with the main-chain to keep some form of log of their activity on the main-chain - this log is key for security. Due to this interaction with the main-chain, which is necessary and recurrent, layer-2 systems impose some load on the main-chain. The impact of such load on the main-chain has been, so far, poorly understood. In addition to that, layer-2 approaches typically sacrifice decentralization and security in favor of higher throughput. This paper presents an experimental study that analyzes the current state of Ethereum layer-2 projects. Our goal is to assess the load they impose on Ethereum and to understand their scalability potential in the long-run. Our analysis shows that the impact of any given layer-2 on the main-chain is the result of both technical aspects (how state is logged on the main-chain) and user behavior (how often users decide to transfer funds between the layer-2 and the main-chain). Based on our observations, we infer that without efficient mechanisms that allow users to transfer funds in a secure and fast manner directly from one layer-2 project to another, current layer-2 systems will not be able to scale Ethereum effectively, regardless of their technical solutions. Furthermore, from our results, we conclude that the layer-2 systems that offer similar security guarantees as Ethereum have limited scalability potential, while approaches that offer better performance, sacrifice security and lead to an increase in centralization which runs against the end-goals of permissionless blockchains.