对SNOW系列算法相关攻击所需连续密钥字最低个数的分析  

Minimum Number of Consecutive Keystream Words for Correlation Attacks on SNOW Family

作　　者：孙莹 SUN Ying(Information Engineering University,Zhengzhou Henan 450001,China)

机构地区：[1]中国人民解放军战略支援部队信息工程大学,河南郑州450001

出　　处：《通信技术》2022年第11期1471-1476,共6页Communications Technology

摘　　要：SNOW系列算法在实际中有着广泛的应用,但目前的研究没有从理论上解释SNOW2.0的单密钥字以及SNOW-V的连续两个时刻密钥字是否与相应的线性反馈移位寄存器(Linear Feedback Shift Register,LFSR)序列存在相关性。基于此,从序列的角度重新定义了相关免疫。通过构造SNOW 2.0、SNOW-V和SNOW-Vi 3个算法前馈变换的复合Walsh谱,证明了其线性逼近中包含的线性逼近单链的相关系数始终为零,从而给出了SNOW 2.0、SNOW-V和SNOW-Vi3个算法与序列相关免疫的最大连续密钥字的长度。该结论从理论上证明了对SNOW 2.0、SNOW-V和SNOW-Vi算法进行相关攻击所需要的连续密钥字的最低个数,为对这些算法进行相关攻击研究提供了理论支撑。The SNOW family of algorithms has a wide range of applications in practice, but the current study does not explain theoretically whether the single keyword of SNOW 2.0 and the two consecutive moment keywords of SNOW-V are correlated with the corresponding LFSR(Linear Feedback Shift Register)sequences. Based on this, this paper redefines correlated immunity from the perspective of stream cipher. By constructing the composite Walsh spectrum of the feedforward transformation for SNOW2.0, SNOW-V and SNOW-Vi, it is proved that the correlation of a linear trail in the linear approximations is always zero, which concludes the maximum number of consecutive keystream words correlation immune to the LFSR sequence for SNOW2.0, SNOW-V and SNOW-Vi. This conclusion theoretically proves the minimum number of consecutive keystream words needed for correlation attacks on SNOW2.0, SNOW-V and SNOW-Vi, and provides theoretical support for the study of correlation attacks on these stream ciphers.

关 键 词：WALSH谱 复合函数 线性逼近 相关免疫 

分 类 号：TN918.1[电子电信—通信与信息系统]