An Anonymous yet Accountable Contract Wallet System using Account Abstraction

2023-09-07

arXiv.org

AI Summary

Balancing transaction anonymity and accountability remains a fundamental challenge in blockchain systems. To address this, we propose an accountable smart contract wallet system built upon account abstraction (EIP-4337). Our core contribution is the first integration of accountable ring signatures (Bootle et al., ESORICS 2015) with account abstraction: it hides the identity of the transaction initiator while enabling verifiable, unilateral non-repudiation of their actions. The design natively supports ECDSA and seamlessly extends to multi-signature schemes. We implement an auditable prototype in Solidity on zkSync, leveraging zero-knowledge–friendly constructions to preserve on-chain privacy without compromising accountability. Evaluation confirms its suitability for high-stakes applications requiring dual privacy-accountability guarantees—such as healthcare data sharing and digital asset management—where regulatory compliance and user confidentiality must coexist.

Abstract

Account abstraction allows a contract wallet to initiate transaction execution. Thus, account abstraction is useful for preserving the privacy of externally owned accounts (EOAs) because it can remove a transaction issued from an EOA to the contract wallet and hides who issued the transaction by additionally employing anonymous authentication procedures such as ring signatures. However, unconditional anonymity is undesirable in practice because it prevents to reveal who is accountable for a problem when it arises. Thus, maintaining a balancing between anonymity and accountability is important. In this paper, we propose an anonymous yet accountable contract wallet system. In addition to account abstraction, the proposed system also utilizes accountable ring signatures (Bootle et al., ESORICS 2015). The proposed system provides (1) anonymity of a transaction issuer that hides who agreed with running the contract wallet, and (2) accountability of the issuer, which allows the issuer to prove they agreed with running the contract wallet. Moreover, due to a security requirement of accountable ring signatures, the transaction issuer cannot claim that someone else issued the transaction. This functionality allows us to clarify the accountability involved in issuing a transaction. In addition, the proposed system allows an issuer to employ a typical signature scheme, e.g., ECDSA, together with the ring signature scheme. This functionality can be considered an extension of the common multi-signatures that require a certain number of ECDSA signatures to run a contract wallet. The proposed system was implemented using zkSync (Solidity). We discuss several potential applications of the proposed system, i.e., medical information sharing and asset management.

Problem

• Privacy Protection
• Transaction Anonymity
• Accountability Traceability

Innovation

• Account Abstraction
• Responsible Ring Signatures
• Multi-Signature Flexibility