Abstract: In recent years,data leakage incidents have occurred frequently,and information security issues have become increasingly prominent.Since a single encryption algorithm cannot meet the security requirements of information in the transmission process,data encryption is generally performed through a hybrid encryption algorithm.The existing hybrid encryption algorithms are mainly based on encryption algorithms designed abroad,which do not meet the autonomous and controllable requirements of cyberspace security.Aiming at this problem,a new hybrid encryption algorithm is designed by combining the improved SM4 algorithm(I-SM4) and SM2 algorithm.It improves the key expansion part of the SM4 encryption algorithm,and uses the linear congruence sequence instead of the original key expansion method to expand the round key,which reduces the correlation between the round keys and improves the security of the key.In addition,the combination of I-SM4 and SM2 can strengthen the management of I-SM4 keys and improve security on the one hand.On the other hand,it can reduce the time required to use the SM2 encryption algorithm alone.Through experiments and analysis,it is proved that the hybrid encryption algorithm proposed in this paper can effectively improve the confidentiality,integrity and non-repudiation of information during network transmission.

Key words: Mixed encryption, SM2, SM3, SM4, Linear congruence