Abstract: As a security transaction framework based on information transaction between blocks, blockchain has a high degree of transparency and decentralization. Zhang Xiaoyan et al. proposed a transaction framework which combines digital commitment and cryptographic algorithm, which can hide the transaction amount during transaction process. However, there are two problems should be considered. First, the recording of the transaction process is operated by trusted full-functional accounting nodes, making the process not decentralized for the blockchain. Secondly, there is also a risk of data leakage during transaction process as the transaction amounts and correlation parameters are required to be transmitted multiple times. In order to solve the above problems, this paper proposes a multi-key homomorphic encryption transaction scheme based on digital commitment with every node records transaction data. The transaction amount hidden in the commitment can be directly updated in the encrypted state, and correlation parameters do not need to be transmitted multiple times. The transaction scheme proposed in this paper has higher efficiency and provable security, which provides a novel idea for the security transaction framework in the blockchain.

Key words: blockchain, digital commitment, homomorphic encryption, multi-keys