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ORBilu is a project developed by
   Characterizing the Impact of Network Delay on Bitcoin MiningCao, Tong  ; Decouchant, Jérémie ; et alScientific Conference (2021, September) Detailed reference viewed: 158 (40 UL)Exploring the Monero Peer-to-Peer NetworkCao, Tong ; ; Decouchant, Jérémie et alin Cao, Tong; Yu, Jiangshan; Decouchant, Jérémie (Eds.) et al Financial Cryptography and Data Security 2020, Sabah, 10-14 February 2020 (2020, February) Detailed reference viewed: 217 (31 UL)Deconstructing Blockchains: A Comprehensive Survey on Consensus, Membership and Structure; ; et al E-print/Working paper (2019) It is no exaggeration to say that since the introduction of Bitcoin, blockchains have become a disruptive technology that has shaken the world. However, the rising popularity of the paradigm has led to a ... [more ▼] It is no exaggeration to say that since the introduction of Bitcoin, blockchains have become a disruptive technology that has shaken the world. However, the rising popularity of the paradigm has led to a flurry of proposals addressing variations and/or trying to solve problems stemming from the initial specification. This added considerable complexity to the current blockchain ecosystems, amplified by the absence of detail in many accompanying blockchain whitepapers. Through this paper, we set out to explain blockchains in a simple way, taming that complexity through the deconstruction of the blockchain into three simple, critical components common to all known systems: membership selection, consensus mechanism and structure. We propose an evaluation framework with insight into system models, desired properties and analysis criteria, using the decoupled components as criteria. We use this framework to provide clear and intuitive overviews of the design principles behind the analyzed systems and the properties achieved. We hope our effort will help clarifying the current state of blockchain proposals and provide directions to the analysis of future proposals. [less ▲] Detailed reference viewed: 107 (6 UL)P3LS : Plausible Deniability for Practical Privacy-Preserving Live StreamingDecouchant, Jérémie ; ; et alScientific Conference (2019, October) Video consumption is one of the most popular Internet activities worldwide. The emergence of sharing videos directly recorded with smartphones raises important privacy concerns. In this paper we propose ... [more ▼] Video consumption is one of the most popular Internet activities worldwide. The emergence of sharing videos directly recorded with smartphones raises important privacy concerns. In this paper we propose P3LS , the first practical privacy-preserving peer-to-peer live streaming system. To protect the privacy of its users, P3LS relies on k-anonymity when users subscribe to streams, and on plausible deniability for the dissemination of video streams. Specifically, plausible deniability during the dissemination phase ensures that an adversary is never able to distinguish a user’s stream of interest from the fake streams from a statistical analysis (i.e., using an analysis of variance). We exhaustively evaluate P3LS and show that adversaries are not able to identify the real stream of a user with very high confidence. Moreover, P3LS consumes 30% less bandwidth than the standard k-anonymity approach where nodes fully contribute to the dissemination of k streams. [less ▲] Detailed reference viewed: 184 (16 UL)Re-thinking untraceability in the CryptoNote-style blockchain; ; Verissimo, Paulo Scientific Conference (2019, June) We develop new foundations on transaction untrace- ability for CryptoNote-style blockchain systems. In particular, we observe new attacks; develop theoretical foundations to model transaction ... [more ▼] We develop new foundations on transaction untrace- ability for CryptoNote-style blockchain systems. In particular, we observe new attacks; develop theoretical foundations to model transaction untraceability; provide the least upper bound of transaction untraceability guarantee; provide ways to efficiently and automatically verify whether a given ledger achieves optimal transaction untraceability; and provide a general solution that achieves provably optimal transaction untraceability. Unlike previous cascade effect attacks (ESORICS’ 17 and PETS’ 18) on CryptoNote-style transaction untraceability, we consider not only a passive attacker but also an active adaptive attacker. Our observed attacks allow both types of attacker to trace blockchain transactions that cannot be traced by using the existing attacks. We develop a series of new games, which we call “The Sun-Tzu Survival Problem”, to model CryptoNote-style blockchain transaction untraceability and our identified attacks. In addition, we obtain seven novel results, where three of them are negative and the rest are positive. In particular, thanks to our abstract game, we are able to build bipartite graphs to model transaction untraceability, and provide reductions to formally relate the hardness of calculating untraceability to the hardness of calculating the number of perfect matchings in all possible bipar- tite graphs. We prove that calculating transaction untraceability is a #P−complete problem, which is believed to be even more difficult to solve than NP problems. In addition, we provide the first result on the least upper bound of transaction untraceability. Moreover, through our theoretical results, we are able to provide ways to efficiently and automatically verify whether a given ledger achieves optimal transaction untraceability. Furthermore, we propose a simple strategy for CryptoNote-style blockchain systems to achieve optimal untraceability. We take Monero as a concrete example to demonstrate how to apply this strategy to optimise the untraceability guarantee provided by Monero. [less ▲] Detailed reference viewed: 190 (13 UL)RepuCoin: Your Reputation is Your Power; ; Decouchant, Jérémie et alin IEEE Transactions on Computers (2019) Existing proof-of-work cryptocurrencies cannot tolerate attackers controlling more than 50% of the network’s computing power at any time, but assume that such a condition happening is “unlikely”. However ... [more ▼] Existing proof-of-work cryptocurrencies cannot tolerate attackers controlling more than 50% of the network’s computing power at any time, but assume that such a condition happening is “unlikely”. However, recent attack sophistication, e.g., where attackers can rent mining capacity to obtain a majority of computing power temporarily, render this assumption unrealistic. This paper proposes RepuCoin, the first system to provide guarantees even when more than 50% of the system’s computing power is temporarily dominated by an attacker. RepuCoin physically limits the rate of voting power growth of the entire system. In particular, RepuCoin defines a miner’s power by its ‘reputation’, as a function of its work integrated over the time of the entire blockchain, rather than through instantaneous computing power, which can be obtained relatively quickly and/or temporarily. As an example, after a single year of operation, RepuCoin can tolerate attacks compromising 51% of the network’s computing resources, even if such power stays maliciously seized for almost a whole year. Moreover, RepuCoin provides better resilience to known attacks, compared to existing proof-of-work systems, while achieving a high throughput of 10000 transactions per second (TPS). [less ▲] Detailed reference viewed: 472 (50 UL) Probabilistic Formal Methods Applied to Blockchain’s Consensus Protocol; ; Rahli, Vincent et alScientific Conference (2018) Detailed reference viewed: 135 (8 UL) |
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