Public blockchain pseudonymity is vulnerable to off-chain cues: external information from sources such as social media or data leaks that can be linked to on-chain activity, enabling user de-anonymization. This paper provides the first comprehensive framework for systematically investigating this threat. We introduce a taxonomy of off-chain cues and propose methodologies to match such cues to blockchain data. Our empirical evaluation on the Ethereum blockchain quantifies the de-anonymization potential of both individual cues and their combinations, as well as real-world case studies such as the Celsius data leak. The results show that cue effectiveness is largely determined by uniqueness and exactness (e.g., specific transaction quantities, interactions with rare tokens), and that combining even a small number of moderately specific cues can significantly reduce anonymity sets. For users revealing multiple such cues, this can lead to the identification of a single on-chain address. In our Celsius simulation, knowledge of only the transaction day, asset, and exact quantity was sufficient to potentially identify over 85% of depositors. Our findings demonstrate the significant privacy risks posed by off-chain cues in blockchain linkage attacks to users disclosing them. Our work underscores the need for heightened user awareness and the development of effective countermeasures.

Privacy-focused cryptoassets like Monero are intentionally difficult to trace. Over the years, several traceability heuristics have been proposed, most of which have been rendered ineffective with subsequent protocol upgrades. Between 2019 and 2023, Monero wallet application bugs “Differ By One” and “10 Block Decoy Bug” have been observed and identified and discussed in the Monero community. In addition, a decentralized mining pool named $\mathbf{P 2 P o o l}$ has proliferated, and a controversial UTXO NFT imitation known as Mordinals has been tried for Monero. In this paper, we systematically describe the traceability heuristics that have emerged from these developments, and evaluate their quality based on ground truth, and through pairwise comparisons. We also explore the temporal perspective, and show which of these heuristics have been applicable over the past years, what fraction of decoys could be eliminated and what the remaining effective ring size is. Our findings illustrate that most of the heuristics have a high precision, that the “ 10 Block Decoy Bug” and the Coinbase decoy identification heuristics have had the most impact between 2019 and 2023, and that the former could be used to evaluate future heuristics, if they are also applicable during that time frame.

We present a measurement study on compositions of Decentralized Finance (DeFi) protocols, which aim to disrupt traditional finance and offer services on top of distributed ledgers, such as Ethereum. Understanding DeFi compositions is of great importance, as they may impact the development of ecosystem interoperability, are increasingly integrated with web technologies, and may introduce risks through complexity. Starting from a dataset of 23 labeled DeFi protocols and 10,663,881 associated Ethereum accounts, we study the interactions of protocols and associated smart contracts. From a network perspective, we find that decentralized exchange (DEX) and lending protocol account nodes have high degree and centrality values, that interactions among protocol nodes primarily occur in a strongly connected component, and that known community detection methods cannot disentangle DeFi protocols. Therefore, we propose an algorithm to decompose a protocol call into a nested set of building blocks that may be part of other DeFi protocols. This allows us to untangle and study protocol compositions. With a ground truth dataset that we have collected, we can demonstrate the algorithm’s capability by finding that swaps are the most frequently used building blocks. As building blocks can be nested, that is, contained in each other, we provide visualizations of composition trees for deeper inspections. We also present a broad picture of DeFi compositions by extracting and flattening the entire nested building block structure across multiple DeFi protocols. Finally, to demonstrate the practicality of our approach, we present a case study that is inspired by the recent collapse of the UST stablecoin in the Terra ecosystem. Under the hypothetical assumption that the stablecoin USD Tether would experience a similar fate, we study which building blocks — and, thereby, DeFi protocols — would be affected. Overall, our results and methods contribute to a better understanding of a new family of financial products.

Machine learning on blockchain graphs is an emerging field with many applications such as ransomware payment tracking, price manipulation analysis, and money laundering detection. However, analyzing blockchain data requires domain expertise and computational resources, which pose a significant barrier and hinder advancement in this field. We introduce Chartalist, the first comprehensive platform to methodically access and use machine learning across a large selection of blockchains to address this challenge. Chartalist contains ML-ready datasets from unspent transaction output (UTXO) (e.g., Bitcoin) and account-based blockchains (e.g., Ethereum). We envision that Chartalist can facilitate data modeling, analysis, and representation of blockchain data and attract a wider community of scientists to analyze blockchains. Chartalist is an open-science initiative at https://github.com/cakcora/Chartalist.

Core decomposition in networks has proven useful for evaluating the importance of nodes and communities in a variety of application domains, ranging from biology to social networks and finance. However, existing core decomposition algorithms have limitations in simultaneously handling multiple node and edge attributes.

Cryptoassets such as cryptocurrencies and tokens are increasingly traded on decentralized exchanges. The advantage for users is that the funds are not in custody of a centralized external entity. However, these exchanges are prone to manipulative behavior. In this paper, we illustrate how wash trading activity can be identified on two of the first popular limit order book-based decentralized exchanges on the Ethereum blockchain, IDEX and EtherDelta. We identify a lower bound of accounts and trading structures that meet the legal definitions of wash trading, discovering that they are responsible for a wash trading volume in equivalent of 159 million U.S. Dollars. While self-trades and two-account structures are predominant, complex forms also occur. We quantify these activities, finding that on both exchanges, more than 30% of all traded tokens have been subject to wash trading activity. On EtherDelta, 10% of the tokens have almost exclusively been wash traded. All data is made available for future research. Our findings underpin the need for countermeasures that are applicable in decentralized systems.