Bitcoin privacy wallet Samourai announced last Thursday that its primary competitor, Wasabi Wallet, is the target of an ongoing network attack.
The blog post is the latest in a string of allegations Samourai has leveled against Wasabi since mid-July.
The attack, according to Samourai Wallet, resembles a Sybil attack, where a small number of users falsifies new identities and pretends to be much larger in number. This would mean that the anonymity set, or crowd, in which a user can hide their bitcoin transactions is not actually as large as Wasabi suggests.
“As the Wasabi team has described it, the goal of the Wasabi mixing technique, is to hide your [unspent transaction outputs] in a ‘sufficiently’ large crowd (peers),” Samourai wrote in its blog post. “The current target Anonymity Set in Wasabi mixing is 100 peers.”
That means that if, say, 20 of those peers are actually just one user and the identity of this user is uncovered, privacy levels for all other users in the same mixing pool are reduced.
“With bad user privacy, the crowd gets smaller,” independent bitcoin researcher Max Hillebrand explained to CoinDesk. “If you are one of these other [transactions] that have not been de-anonymized [by an attacker] then your anonymity set is no longer 100.”
Samourai says evidence of Sybil attacks on the Wasabi network dates back to January 2019.
Wasabi has issued its own statements refuting Samourai’s claims, while also issuing allegations of their own against Samourai.
As a result, privacy-minded bitcoin users are questioning the true efficacy of either wallet in hiding the identities of its users.