Lightweight Privacy-Preserving Mechanisms for Cross-Chain Transactions

The widespread developments of blockchain bring about diverse blockchain networks, where each stands as an isolated data island and operates independently. The need of interoperability and interconnection among kinds of blockchains inspires the emergence of the cross-chain technology. It enables the asset transfer and information interaction via crosschain transactions. The previous cross-chain transaction systems are almost implemented over the plain data, fully exposing the transaction-associated information. Cryptographic techniques such as non-interactive zero-knowledge proof can be used to protect the transaction privacy, while its high complexity incurs heavy running cost. The privacy of cross-chain transactions is still a challenging issue. In this paper, we propose a lightweight crosschain transaction privacy-preserving method named PTCross. It embeds Bulletproofs and Pedersen commitment to hide crosschain transaction information, meanwhile combining off-chain computation and on-chain contract verification. We instantiate and implement PTCross between ChainMaker and Bitcoin. The experimental results show that the proposed PTCross achieves both lightweight performance and strong privacy.