Abstract: As a core technology of the blockchain, the smart contract is receiving increasing attention. However, the frequent outbreak of smart contract security events shows that improving the security of smart contracts is essential. How to guarantee the privacy of contract execution and the correctness of calculation results at the same time is still an issue to be resolved. Using secure multi-party computation (SMPC) technology to implement smart contracts is considered to be one of the potential solutions. But in the existing SMPC based contract execution schemes, a problem has been ignored, that is, the attacker can perform the same process as the reconstructor to recover the secret, which leads to the leakage of users' privacy. Therefore, in order to solve this problem in the process of smart contract operation, an improved homomorphic encryption algorithm is proposed in this paper, which has a relatively small public key size, short ciphertext length, and high encryption efficiency. Then, a contract execution scheme integrated with SMPC and homomorphic encryption (SMPC-HE for short) is further proposed, which is able to guarantee the privacy of contract execution and the correctness of the calculation results at the same time, and also makes smart contract execution fairer. Finally, our scheme is proved secure, efficient and has low space overhead by theory and experiment results.
Authors: Zhaoxuan Li and Rui Zhang (Institute of Information Engineering, Chinese Academy of Sciences, China); Pengchao Li (Chinese Academy of Sciences, China)
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