Journal of Xidian University ›› 2021, Vol. 48 ›› Issue (1): 87-95.doi: 10.19665/j.issn1001-2400.2021.01.010

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Efficient multi-key fully homomorphic encryption scheme from RLWE

CHE Xiaoliang1,2(),ZHOU Haonan2(),YANG Xiaoyuan1,2(),ZHOU Tanping1,2(),LIU Longfei1(),LI Ningbo2()   

  1. 1. College of Cryptographic Engineering,Engineering University of PAP,Xi’an 710086,China
    2. Key Laboratory of Network and Information Security of the PAP,Xi’an 710086,China
  • Received:2020-08-14 Online:2021-02-20 Published:2021-02-03
  • Contact: Xiaoyuan YANG,Tanping ZHOU;;;;;


The ring-LWE-based BGV-type multi-key fully homomorphic encryption (MKFHE) scheme has a large size of ciphertexts and keys,and the generation process of evaluation key is complicated,which results in a low homomorphic evaluating efficiency.To improve these problems,a BGV-type MKFHE scheme with a small-size key and a high efficiency of evaluation of key generation is proposed.First,by modifying the expansion of the ciphertext,the algorithm for generation of the evaluation key is optimized and the efficiency of the algorithm is improved.Second,the low bit discarding technique is used in the generation algorithm,which reduces the calculated redundancy and decreases the calculated complexity.Finally,by applying modulus-switching and key-switching techniques to the optimized algorithm,an efficient leveled BGV-type MKFHE scheme with IND-CPA security is proposed.Compared with the previous leveled BGV-type MKFHE schemes,the proposed scheme can simplify the process of generation of the evaluation key and decrease memory (bit-size) and calculation costs.Moreover,the proposed scheme has a higher efficiency and a less noise magnitude.

Key words: multi-key fully homomorphic encryption, ciphertext expansion algorithm, evaluation key, key-switching, hybrid homomorphic multiplication

CLC Number: 

  • TP309