Vitalik Buterin, one of the founders of Ethereum, has released a research paper that delves into the concept of privacy pool systems, aiming to enhance privacy in financial transactions.
These systems allow users to demonstrate their separation from illicit funds by utilizing zero-knowledge-proof technology.
The document initially explores Tornado Cash, a widely used privacy-enhancing protocol that permits users to deposit and withdraw cryptocurrencies without creating identifiable connections between their addresses. Recently, the founders of Tornado Cash faced criminal charges in the United States, citing extensive misuse by malicious actors.
The research paper points out a significant problem with Tornado Cash: legitimate users had limited means to disassociate themselves from the protocol’s criminal activities.
The paper suggests an extension of Tornado Cash’s approach. This extension would enable users to publicly verify the source of their funds on the blockchain, accomplishing this through membership proofs and exclusion proofs.
According to the authors, this concept could strike a balance between honest and dishonest protocol users, potentially paving the way for on-chain financial compliance in the future. The core idea of this proposal is to allow users to publish a zero-knowledge proof demonstrating the origin of their funds from known lawful or unlawful sources. Importantly, this is achieved without revealing their complete transaction history.
Users do this by proving membership in customized association sets that meet specific properties mandated by regulations or societal consensus.
In privacy pools, users can exclude themselves from anonymity groups containing addresses linked to illegal activities through zero-knowledge proofs. Instead of merely proving that a withdrawal is connected to a prior deposit, this approach focuses on proving membership in a more tightly defined association set.
The association set can encompass all past deposits, only the user’s deposits, or anything in between, according to Cointelegraph. Users specify this set using its Merkle root as public input. To simplify, the system doesn’t directly prove that the association set is a subset of prior deposits; it requires users to zero-knowledge-proof two Merkle branches.
The paper also presents various other use cases for zero-knowledge proofs, allowing users to demonstrate that their funds are unrelated to illicit sources or to prove their funds originate from a specific set of deposits without disclosing further details.
In many cases, privacy and regulatory compliance are seen as conflicting goals. However, the paper suggests that this doesn’t have to be the case if privacy-enhancing protocols enable users to prove specific properties about the origin of their funds.
The paper concludes by noting that protocols focusing on zero-knowledge solutions are gaining prominence, particularly within the Ethereum network, and predicts that scaling ZK-proof solutions will see substantial growth in the next year as global regulations evolve and users increasingly seek to protect their privacy.