基于NTRU的多密钥同态加密方案解密结构  

Decryption structure of multi-key homomorphic encryption scheme based on NTRU

作　　者：车小亮 周昊楠[1] 周潭平 李宁波 杨晓元[1,2] CHE Xiaoliang;ZHOU Haonan;ZHOU Tanping;LI Ningbo;YANG Xiaoyuan(College of Cryptographic Engineering,Engineering University of PAP,Xian Shaanxi 710086,China;Key Laboratory of Network and Information Security of PAP,Xi'an Shaanxi 710086,China)

机构地区：[1]武警工程大学密码工程学院,西安710086 [2]网络与信息安全武警部队重点实验室,西安710086

出　　处：《计算机应用》2020年第7期1959-1964,共6页journal of Computer Applications

基　　金：国家重点研发计划项目(2017YFB0802000);国家自然科学基金资助项目(U1636114);国家密码发展基金资助项目(MMJJ20170112)。

摘　　要：为了进一步提升NTRU型多密钥全同态加密(MKFHE)方案的安全性和效率,基于素数幂次分圆多项式环,研究了NTRU型多密钥同态加密的原始解密结构特点,并提出了两种多密钥同态解密结构改进优化方法。首先通过降低多项式系数,设计了"Regev-Style"多密钥解密结构;其次通过扩展密文维度,设计了"Ciphertext-Expansion"多密钥解密结构。通过与NTRU型多密钥同态加密方案的原始解密结构进行对比分析,结果表明"Regev-Style"多密钥解密结构降低了产生噪声的量级,用于NTRU型多密钥全同态加密方案设计时能减少密钥交换次数和模交换次数;"Ciphertext-Expansion"多密钥解密结构消除了密钥交换过程,降低了产生噪声的量级,且能更有效地处理重复用户的密文乘积。改进优化的多密钥解密结构的安全性均基于素数幂次分圆多项式环上的误差学习(LWE)问题和判定小多项式比(DSPR)假设,这些结构能较好地抵御子域攻击。通过选取合适的参数,它们可用于设计更加安全高效的NTRU型多密钥全同态加密方案。In order to further improve the security and efficiency of Number Theory Research Unit(NTRU)-type MultiKey Fully Homomorphic Encryption(MKFHE)schemes,based on the prime power cyclotomic rings,the properties of the original decryption structure of NTRU-type multi-key fully homomorphic encryption were studied,and two optimization methods of multi-key homomorphic decryption structures were proposed.Firstly,by reducing the polynomial’s coefficients,the"Regev-Style"multi-key decryption structure was designed.Secondly,the"Ciphertext-Expansion"multi-key decryption structure was designed by expanding the dimension of ciphertexts.Compared with the original decryption structure of NTRUtype multi-key homomorphic encryption scheme,the"Regev-Style"multi-key decryption structure reduced the magnitude of error,which was able to reduce the number of key-switching and modulo-switching when it was used in the design of NTRUtype multi-key homomorphic encryption scheme;the"Ciphertext-Expansion"multi-key decryption structure eliminated the key-switching operation,reduced the magnitude of error,and was able to process the ciphertext product of repeated users more effectively.The security of the optimized multi-key decryption structures was based on the Learning With Errors(LWE)problem and Decisional Small Polynomial Ratio(DSPR)assumption on the prime power cyclotomic rings,so these structures were able to resist subfield attacks well.Therefore,they can be used to design a more secure and efficient NTRUtype multi-key fully homomorphic encryption scheme by selecting appropriate parameters.

关 键 词：NTRU型多密钥同态加密 素数幂次分圆多项式环 同态乘法解密结构 小系数多项式 密文扩展 

分 类 号：TP309[自动化与计算机技术—计算机系统结构]