PCT: A Relay-Based Privacy-Preserving Cross-Chain Transaction Scheme

Blockchain has been rapidly evolving in recent years and widely used in financial transactions due to its tamper-proof and decentralization features. However, as a relatively independent system, different blockchains have difficulty interoperating with each other, and the issue of "Value Island" becomes more problematic. In addition, the users on the different ledgers are also concerned about the leakage of privacy in the cross-chain process. In this paper, we propose a Privacy-Preserving Cross-Chain Transaction (PCT) scheme combining the relay mechanism with the hash locking mechanism. Meanwhile, the Pedersen commitment is introduced to enable the committers to verify the transaction without acknowledging the amount. We also conduct the range proof based on the Borromean ring signature to ensure that the transaction amount is legitimate. Finally, a lending scheme is designed to solve the problem of insufficient funds in cross-chain transactions. Security analysis and experiments show our scheme achieves privacy-preserving cross-chain transactions with low overhead.