8 research outputs found
Tracing Transactions Across Cryptocurrency Ledgers
One of the defining features of a cryptocurrency is that its ledger,
containing all transactions that have evertaken place, is globally visible. As
one consequenceof this degree of transparency, a long line of recent re-search
has demonstrated that even in cryptocurrenciesthat are specifically designed to
improve anonymity it is often possible to track money as it changes hands,and
in some cases to de-anonymize users entirely. With the recent proliferation of
alternative cryptocurrencies, however, it becomes relevant to ask not only
whether ornot money can be traced as it moves within the ledgerof a single
cryptocurrency, but if it can in fact be tracedas it moves across ledgers. This
is especially pertinent given the rise in popularity of automated trading
platforms such as ShapeShift, which make it effortless to carry out such
cross-currency trades. In this paper, weuse data scraped from ShapeShift over a
thirteen-monthperiod and the data from eight different blockchains to explore
this question. Beyond developing new heuristics and creating new types of links
across cryptocurrency ledgers, we also identify various patterns of
cross-currency trades and of the general usage of these platforms, with the
ultimate goal of understanding whetherthey serve a criminal or a profit-driven
agenda.Comment: 14 pages, 13 tables, 6 figure
Alt-Coin Traceability
Many alt-coins developed in recent years make strong privacy guarantees, claiming to be virtually untraceable. This paper explores the extent to which these claims are true after the first appraisals were made about these coins. In particular, we will investigate Monero (XMR) and Zcash (ZEC), competitors in the private cryptocurrency space. We will test how traceable these currencies are after the most recent security updates, and how they hold up against their claims. We run some traceability experiments based on previously published papers for each coin. Results show that, introducing strict security and anonymity requirements into the cryptocurrency ecosystem makes the coin effectively untraceable, as shown by Monero. On the other hand, Zcash still hesitates to introduce changes that alter user behavior. Despite its strong cryptographic features, transactions are overall more traceable
An Empirical Analysis of Privacy in the Lightning Network
Payment channel networks, and the Lightning Network in particular, seem to
offer a solution to the lack of scalability and privacy offered by Bitcoin and
other blockchain-based cryptocurrencies. Previous research has focused on the
scalability, availability, and crypto-economics of the Lightning Network, but
relatively little attention has been paid to exploring the level of privacy it
achieves in practice. This paper presents a thorough analysis of the privacy
offered by the Lightning Network, by presenting several attacks that exploit
publicly available information about the network in order to learn information
that is designed to be kept secret, such as how many coins a node has available
or who the sender and recipient are in a payment routed through the network.Comment: 26 pages, 5 figure
On Defeating Graph Analysis of Anonymous Transactions
In a ring-signature-based anonymous cryptocurrency, signers of a transaction are hidden among a set of potential signers, called a ring, whose size is much smaller than the number of all users. The ring-membership relations specified by the sets of transactions thus induce bipartite transaction graphs, whose distribution is in turn induced by the ring sampler underlying the cryptocurrency.
Since efficient graph analysis could be performed on transaction graphs to potentially deanonymise signers, it is crucial to understand the resistance of (the transaction graphs induced by) a ring sampler against graph analysis. Of particular interest is the class of partitioning ring samplers. Although previous works showed that they provide almost optimal local anonymity, their resistance against global, e.g. graph-based, attacks were unclear.
In this work, we analyse transaction graphs induced by partitioning ring samplers. Specifically, we show (partly analytically and partly empirically) that, somewhat surprisingly, by setting the ring size to be at least logarithmic in the number of users, a graph-analysing adversary is no better than the one that performs random guessing in deanonymisation up to constant factor of 2
On Sustainable Ring-based Anonymous Systems
Anonymous systems (e.g. anonymous cryptocurrencies and updatable anonymous credentials) often follow a construction template where an account can only perform a single anonymous action, which in turn potentially spawns new (and still single-use) accounts (e.g. UTXO with a balance to spend or session with a score to claim). Due to the anonymous nature of the action, no party can be sure which account has taken part in an action and, therefore, must maintain an ever-growing list of potentially unused accounts to ensure that the system keeps running correctly. Consequently, anonymous systems constructed based on this common template are seemingly not sustainable.
In this work, we study the sustainability of ring-based anonymous systems, where a user performing an anonymous action is hidden within a set of decoy users, traditionally called a ``ring\u27\u27.
On the positive side, we propose a general technique for ring-based anonymous systems to achieve sustainability. Along the way, we define a general model of decentralised anonymous systems (DAS) for arbitrary anonymous actions, and provide a generic construction which provably achieves sustainability. As a special case, we obtain the first construction of anonymous cryptocurrencies achieving sustainability without compromising availability. We also demonstrate the generality of our model by constructing sustainable decentralised anonymous social networks.
On the negative side, we show empirically that Monero, one of the most popular anonymous cryptocurrencies, is unlikely to be sustainable without altering its current ring sampling strategy. The main subroutine is a sub-quadratic-time algorithm for detecting used accounts in a ring-based anonymous system
Deconstructing Blockchains: A Comprehensive Survey on Consensus, Membership and Structure
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