A distributed cross-chain mechanism based on notary schemes and group signatures

Blockchain technology has attracted significant attention since its publication. However, most existing blockchain platforms are isolated systems, which makes it difficult to exchange data among different blockchains. The industry has proposed the notary schemes to enhance blockchain interoperability, which can exchange messages among different blockchains through a notary. However, conventional notary schemes are centralized, which suffers from single point of failures. To address these issues, this paper proposes a distributed cross-chain notary model with regulatory mechanisms, based on improved threshold group signatures. We improve the group signature scheme by setting up a group of tracing authorities to achieve distributed tracing. Furthermore, we incorporate this signature scheme into our notary scheme, where a group of notaries signs cross-chain transactions using group signatures. We also introduce a group of regulators to reveal the true identities of malicious notaries when disputes occur. Finally, we prove the security of our signature scheme based on the Random Oracle Model. In our experiments, when the number of notaries is 102 and the threshold is 2/3 of that, it takes 166 ms to set up and generate signature. Also, it takes 161 ms for regulators to reveal the true identities of malicious notaries.