Cache计时攻击对ElGamal签名的安全威胁分析

Analysis of Vulnerability in EIGamal Signature Due to Cache Timing Attack

分析了E1Gamal签名中模幂运算的平方乘算法和滑动窗口算法，给出了两种算法下利用Cache计时采集旁路信息的方法和幂指数恢复算法，分析了Cache计时攻击对幂指数相关的旁路信息获取能力以及Cache计时攻击对E1Gamal签名的安全性威胁．通过仿真验证了Cache计时攻击能够有效获取旁路信息，展示了不同长度随机密钥的安全等级，给出了建议采用的随机密钥长度与可能的防御措施．

This paper analyzes square-multiplication method and sliding window method for modular exponentiation used in ElGamal signature, and proposes corresponding technology of collecting side channel information with Cache timing and algorithms for recovering exponent. The ability to gain exponent-related side channel information and the impact on E1Gamal signature are analyzed. The results of simulation experiment demonstrate the ability of Cache tim ing attack and show the security levels of varied keysizes. The suggested keysize of nonce and pos- sible countermeasures are pointed out.