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Autori principali: Gavenda, Jiri, Svenda, Petr, Bobon, Stanislav, Sedlacek, Vladimir
Natura: Preprint
Pubblicazione: 2025
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Accesso online:https://arxiv.org/abs/2510.17284
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author Gavenda, Jiri
Svenda, Petr
Bobon, Stanislav
Sedlacek, Vladimir
author_facet Gavenda, Jiri
Svenda, Petr
Bobon, Stanislav
Sedlacek, Vladimir
contents A coinjoin protocol aims to increase transactional privacy for Bitcoin and Bitcoin-like blockchains via collaborative transactions, by violating assumptions behind common analysis heuristics. Estimating the resulting privacy gain is a crucial yet unsolved problem due to a range of influencing factors and large computational complexity. We adapt the BlockSci on-chain analysis software to coinjoin transactions, demonstrating a significant (10-50%) average post-mix anonymity set size decrease for all three major designs with a central coordinator: Whirlpool, Wasabi 1.x, and Wasabi 2.x. The decrease is highest during the first day and negligible after one year from a coinjoin creation. Moreover, we design a precise, parallelizable privacy estimation method, which takes into account coinjoin fees, implementation-specific limitations and users' post-mix behavior. We evaluate our method in detail on a set of emulated and real-world Wasabi 2.x coinjoins and extrapolate to its largest real-world coinjoins with hundreds of inputs and outputs. We conclude that despite the users' undesirable post-mix behavior, correctly attributing the coins to their owners is still very difficult, even with our improved analysis algorithm.
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publishDate 2025
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spellingShingle Analysis of Input-Output Mappings in Coinjoin Transactions with Arbitrary Values
Gavenda, Jiri
Svenda, Petr
Bobon, Stanislav
Sedlacek, Vladimir
Cryptography and Security
A coinjoin protocol aims to increase transactional privacy for Bitcoin and Bitcoin-like blockchains via collaborative transactions, by violating assumptions behind common analysis heuristics. Estimating the resulting privacy gain is a crucial yet unsolved problem due to a range of influencing factors and large computational complexity. We adapt the BlockSci on-chain analysis software to coinjoin transactions, demonstrating a significant (10-50%) average post-mix anonymity set size decrease for all three major designs with a central coordinator: Whirlpool, Wasabi 1.x, and Wasabi 2.x. The decrease is highest during the first day and negligible after one year from a coinjoin creation. Moreover, we design a precise, parallelizable privacy estimation method, which takes into account coinjoin fees, implementation-specific limitations and users' post-mix behavior. We evaluate our method in detail on a set of emulated and real-world Wasabi 2.x coinjoins and extrapolate to its largest real-world coinjoins with hundreds of inputs and outputs. We conclude that despite the users' undesirable post-mix behavior, correctly attributing the coins to their owners is still very difficult, even with our improved analysis algorithm.
title Analysis of Input-Output Mappings in Coinjoin Transactions with Arbitrary Values
topic Cryptography and Security
url https://arxiv.org/abs/2510.17284