Exploring the Monero Peer-to-Peer Network

in Cao, Tong; Yu, Jiangshan; Decouchant, Jérémie (Eds.) et al Financial Cryptography and Data Security 2020, Sabah, 10-14 February 2020 (2020, February)

Deconstructing Blockchains: A Comprehensive Survey on Consensus, Membership and Structure

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 ▲]

Re-thinking untraceability in the CryptoNote-style blockchain

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 ▲]

RT-ByzCast: Byzantine-Resilient Real-Time Reliable Broadcast

in IEEE Transactions on Computers (2019), 68(3),

Today’s cyber-physical systems face various impediments to achieving their intended goals, namely, communication uncertainties and faults, relative to the increased integration of networked and wireless ... [more ▼]

Today’s cyber-physical systems face various impediments to achieving their intended goals, namely, communication uncertainties and faults, relative to the increased integration of networked and wireless devices, hinder the synchronism needed to meet real-time deadlines. Moreover, being critical, these systems are also exposed to significant security threats. This threat combination increases the risk of physical damage. This paper addresses these problems by studying how to build the first real-time Byzantine reliable broadcast protocol (RTBRB) tolerating network uncertainties, faults, and attacks. Previous literature describes either real-time reliable broadcast protocols, or asynchronous (non real-time) Byzantine ones. We first prove that it is impossible to implement RTBRB using traditional distributed computing paradigms, e.g., where the error/failure detection mechanisms of processes are decoupled from the broadcast algorithm itself, even with the help of the most powerful failure detectors. We circumvent this impossibility by proposing RT-ByzCast, an algorithm based on aggregating digital signatures in a sliding time-window and on empowering processes with self-crashing capabilities to mask and bound losses. We show that RT-ByzCast (i) operates in real-time by proving that messages broadcast by correct processes are delivered within a known bounded delay, and (ii) is reliable by demonstrating that correct processes using our algorithm crash themselves with a negligible probability, even with message loss rates as high as 60%. [less ▲]

ANCHOR: logically-centralized security for Software-Defined Networks

E-print/Working paper (2019)

Software-de ned networking (SDN) decouples the control and data planes of traditional networks, logically centralizing the functional properties of the network in the SDN controller. While this ... [more ▼]

Software-de ned networking (SDN) decouples the control and data planes of traditional networks, logically centralizing the functional properties of the network in the SDN controller. While this centralization brought advantages such as a faster pace of innovation, it also disrupted some of the natural defenses of traditional architectures against di erent threats. The literature on SDN has mostly been concerned with the functional side, despite some speci c works concerning non-functional properties like ‘security’ or ‘dependability’. Though addressing the latter in an ad-hoc, piecemeal way, may work, it will most likely lead to e ciency and e ectiveness problems. We claim that the enforcement of non-functional properties as a pillar of SDN robustness calls for a systemic approach. We further advocate, for its materialization, the re-iteration of the successful formula behind SDN – ‘logical centralization’. As a general concept, we propose anchor, a subsystem architecture that promotes the logical centralization of non-functional properties. To show the e ectiveness of the concept, we focus on ‘security’ in this paper: we identify the current security gaps in SDNs and we populate the architecture middleware with the appropriate security mechanisms, in a global and consistent manner. anchor sets to provide essential security mechanisms such as strong entropy, resilient pseudo-random generators, secure device registration and association, among other crucial services. We claim and justify in the paper that centralizing such mechanisms is key for their e ectiveness, by allowing us to: de ne and enforce global policies for those properties; reduce the complexity of controllers and forwarding devices; ensure higher levels of robustness for critical services; foster interoperability of the non-functional property enforcement mechanisms; and nally, better foster the resilience of the architecture itself. We discuss design and implementation aspects, and we prove and evaluate our algorithms and mechanisms. [less ▲]

Asphalion: Trustworthy Shielding Against Byzantine Faults

in Vukotic, Ivana; Rahli, Vincent; Verissimo, Paulo (Eds.) Asphalion: Trustworthy Shielding Against Byzantine Faults (2019)

Byzantine Resilient Protocol for the IoT

in IEEE Internet of Things Journal (2018)

Wireless sensor networks, often adhering to a single gateway architecture, constitute the communication backbone for many modern cyber-physical systems. Consequently, faulttolerance in CPS becomes a ... [more ▼]

Wireless sensor networks, often adhering to a single gateway architecture, constitute the communication backbone for many modern cyber-physical systems. Consequently, faulttolerance in CPS becomes a challenging task, especially when accounting for failures (potentially malicious) that incapacitate the gateway or disrupt the nodes-gateway communication, not to mention the energy, timeliness, and security constraints demanded by CPS domains. This paper aims at ameliorating the fault-tolerance of WSN based CPS to increase system and data availability. To this end, we propose a replicated gateway architecture augmented with energy-efficient real-time Byzantineresilient data communication protocols. At the sensors level, we introduce FT-TSTP, a geographic routing protocol capable of delivering messages in an energy-efficient and timely manner to multiple gateways, even in the presence of voids caused by faulty and malicious sensor nodes. At the gateway level, we propose a multi-gateway synchronization protocol, which we call ByzCast, that delivers timely correct data to CPS applications, despite the failure or maliciousness of a number of gateways. We show, through extensive simulations, that our protocols provide better system robustness yielding an increased system and data availability while meeting CPS energy, timeliness, and security demands. [less ▲]

Intrusion-Tolerant Autonomous Driving

in Proceedings of 2018 IEEE 21st International Symposium on Real-Time Distributed Computing (ISORC) (2018, May 29)

Fully autonomous driving is one if not the killer application for the upcoming decade of real-time systems. However, in the presence of increasingly sophisticated attacks by highly skilled and well ... [more ▼]

Fully autonomous driving is one if not the killer application for the upcoming decade of real-time systems. However, in the presence of increasingly sophisticated attacks by highly skilled and well equipped adversarial teams, autonomous driving must not only guarantee timeliness and hence safety. It must also consider the dependability of the software concerning these properties while the system is facing attacks. For distributed systems, fault-and-intrusion tolerance toolboxes already offer a few solutions to tolerate partial compromise of the system behind a majority of healthy components operating in consensus. In this paper, we present a concept of an intrusion-tolerant architecture for autonomous driving. In such a scenario, predictability and recovery challenges arise from the inclusion of increasingly more complex software on increasingly less predictable hardware. We highlight how an intrusion tolerant design can help solve these issues by allowing timeliness to emerge from a majority of complex components being fast enough, often enough while preserving safety under attack through pre-computed fail safes. [less ▲]

MaskAl: Privacy Preserving Masked Reads Alignment using Intel SGX

Scientific Conference (2018)

The recent introduction of new DNA sequencing techniques caused the amount of processed and stored biological data to skyrocket. In order to process these vast amounts of data, bio-centers have been ... [more ▼]

The recent introduction of new DNA sequencing techniques caused the amount of processed and stored biological data to skyrocket. In order to process these vast amounts of data, bio-centers have been tempted to use low-cost public clouds. However, genomes are privacy sensitive, since they store personal information about their donors, such as their identity, disease risks, heredity and ethnic origin. The first critical DNA processing step that can be executed in a cloud, i.e., read alignment, consists in finding the location of the DNA sequences produced by a sequencing machine in the human genome. While recent developments aim at increasing performance, only few approaches address the need for fast and privacy preserving read alignment methods. This paper introduces MaskAl, a novel approach for read alignment. MaskAl combines a fast preprocessing step on raw genomic data — filtering and masking — with established algorithms to align sanitized reads, from which sensitive parts have been masked out, and refines the alignment score using the masked out information with Intel’s software guard extensions (SGX). MaskAl is a highly competitive privacy-preserving read alignment software that can be massively parallelized with public clouds and emerging enclave clouds. Finally, MaskAl is nearly as accurate as plain-text approaches (more than 96% of aligned reads with MaskAl compared to 98% with BWA) and can process alignment workloads 87% faster than current privacy-preserving approaches while using less memory and network bandwidth. [less ▲]

Probabilistic Formal Methods Applied to Blockchain’s Consensus Protocol

Scientific Conference (2018)