Abstract: The development of information technology and network communication promotes the emergence of big data and cloud computing.The security and privacy of user’s data have gradually become the focus of academic research.Fully Homomorphic Encryption (FHE) is a new research subject,and it has a broad application prospect and important research significance in recent years.It supports arbitrary computation on encrypted data which is equivalent to do the same operations on corresponding plaintext.This feature has important applications in the security of cloud computing.In 2011,Lauter et al. proposed a RLWE-based Homomorphic Encryption scheme,aiming at the scheme,this paper designed a new scheme combined with the batch technique.Concretely,the technique packs multiple “plaintext slots” into a ciphertext by using the Chinese Remainder Theorem,and then performs homomorphic operations on it.Considering the exponential growth of the noise in each multiplication operation,this paper used the key switch and module switch technique to reduce the noise size in ciphertext,which ensure the correct decryption and the next homomorphic computation.Finally,this paper analyzed the security and efficiency of the scheme.It is proved that the proposed scheme is CPA security and the efficiency of encryption is n times to the original scheme.

Key words: Batch technique, Fully homomorphic encryption, Key switch, Module switch