bitcoin-dev
Combined summary - Reiterating centralized coinjoin (Wasabi & Samourai) deanonymization attacks
The discourse on the vulnerabilities within coinjoin implementations like Wasabi and GingerWallet, alongside their protocols, unveils significant deanonymization risks that stem from fundamental design issues rather than recent discoveries.
A critical examination reveals a deep-seated mistrust between users and coordinators, exacerbated by rent-seeking behavior and alleged incompetence. This skepticism is deeply rooted in the initial involvement in the design of WabiSabi—a protocol intended for these wallets—highlighting persistent concerns over its suitability.
In the case of Whirlpool, a key vulnerability lies in the manipulation of blind signing keys by malicious coordinators, potentially linking transaction outputs to inputs through the provision of unique RSA keys for each input during confirmation phases. This mechanism starkly contradicts the privacy assurances purported by the protocol. Similarly, WabiSabi faces challenges with key consistency; the protocol's reliance on clients independently registering Bitcoin UTXOs, coupled with the potential issuance of inconsistent round IDs, opens avenues for partitioning and deanonymization. Despite attempts to mitigate these risks through adjustments in ownership proof distributions, the core issue persists, primarily due to inadequate control over the verification mechanisms for public keys used in proofs.
The discussions extend to additional concerns such as coin selection practices, timing of input registrations, and Tor circuit management, all of which heighten the susceptibility to deanonymization attacks. The use of JSON and HTTP in the protocol further introduces unwanted variability in data serialization, potentially compromising user privacy. Moreover, economic incentives built into the system, including coordination fees and anonymous credential mechanisms, have failed to prevent theft of user funds, underscoring a glaring oversight in balancing privacy concerns with financial security for users.
This dialogue reflects the ongoing challenge within the Bitcoin development community to innovate while maintaining high standards of security and user trust. It highlights the intricate balance required between advancing privacy-enhancing technologies and safeguarding against exploitation and misuse, showcasing the complexities involved in evolving cryptocurrency protocols to meet the privacy demands of users amidst prevailing risks.