<p>Most existing blockchain platforms cannot transfer assets and messages with other blockchains, which renders them isolated systems. As a kind of cross-chain mechanism, the notary scheme can introduce a notary to forward transactions between different blockchains to enhance blockchain interoperability. However, the notary scheme lacks privacy-preserving mechanisms, which makes users’ private information vulnerable to malicious attacks. To address this issue, this paper proposes a privacy-preserving notary scheme based on zero-knowledge proofs. We combine the existing BlockMaze scheme with notary schemes to ensure that the sender, recipient, and amount of cross-chain transactions are hidden from outsiders. Furthermore, the notary group will use traceable group signatures to sign on cross-chain transactions. When the received transactions are reported illegally, the regulator group can trace the real identities of malicious notaries through the signatures to protect users’ assets. Finally, we conducted a theoretical analysis of the proposed scheme from the perspectives of correctness, anonymity, and security. The correctness analysis verified the consistency of the keys during the execution of the scheme, the anonymity analysis examined the privacy protection of the sender, receiver, and transaction amounts during the transaction process, and the security analysis evaluated the scheme’s defense capabilities against common attacks. Moreover, experimental results demonstrated that the proposed scheme has significantly improved efficiency compared to existing schemes, particularly regarding computational cost and time consumption when handling large prime numbers.</p>