bitcoin-dev
Reiterating centralized coinjoin (Wasabi & Samourai) deanonymization attacks
Posted on: January 7, 2025 21:33 UTC
The discourse delves into the intricacies and misconceptions surrounding privacy mechanisms, particularly focusing on the limitations of certain technologies that are often misconceived as privacy-enhancing.
It brings to light the issue with wabisabi credentials, which, contrary to popular belief, do not inherently improve privacy but offer resistance to denial of service (DoS) attacks without compromising privacy. The narrative highlights a significant oversight in Wasabi's full node support concerning the implementation of checks for light clients, suggesting possible mitigations to strengthen resistance against exploitation.
An alarming aspect discussed is the susceptibility of protocols to misuse, exemplified by the first three Wasabi protocols possessing cryptographic flaws in their DoS protection. This vulnerability was later exploited through misconfiguration rather than direct attacks on the protocol itself, leading to the adoption of Cloudflare with SSL termination as a remedial measure. The critique extends to the auditing practices, where audits focused solely on protocol security from the coordinator's perspective, neglecting the non-cryptographic, privacy-sensitive code that protects clients. This oversight underscores a broader issue of transparency and accountability, with the audit announcement failing to communicate the limited scope of the security review.
The discussion further explores the technical challenges and potential solutions in safeguarding privacy and ensuring security in transaction coordination. One such solution involves publishing ownership proofs, which could mitigate various tagging concerns, albeit this practice was initially overlooked in Wasabi's release strategy. The complexity of achieving privacy and security simultaneously is evident in the analysis of coordinator fee support and the vulnerabilities associated with transcript equivocation, highlighting the intricate balance between preventing abuse and maintaining user privacy.
Moreover, the conversation sheds light on the persistent issues of passive deanonymization tactics, stemming from problematic coin selection methods and potential timing leaks in tor circuit management. These vulnerabilities are exacerbated by the use of HTTP and JSON at the protocol level, introducing semantic leaks that could be exploited to compromise privacy. The critique points out the inadequate response to these concerns, emphasizing the ethical implications of exploiting users' privacy for profit.
In summary, the dialogue critically examines the challenges and misconceptions in implementing privacy-preserving technologies, emphasizing the need for comprehensive security measures, transparency in auditing, and ethical considerations in the development and deployment of such technologies.