SHA-512算法及其基于生日攻击的安全性分析

SHA-512 Algorithm and Its Security Analysis Based on Birthday Attack

生日攻击是一种通用的碰撞攻击方法,它可用于攻击任何类型的散列函数。分析了SHA-512的算法原理,讨论了生日攻击的碰撞阈值和攻击步骤,并对SHA-512算法在生日攻击下的安全性进行了分析。通过分析得出SHA-512所有消息块处理完后得到了8个64位变量H0-H7的数据级联,并且输出散列码是512位,这对于攻击者来说是不可预测的,猜中的概率可以忽略,而找到目标消息的碰撞的计算复杂度为2256。所以,相对来说SHA-512的安全性比MD5,SHA-1等要高,采用SHA-512后将更能抵抗生日攻击,并能抵御已知密码分析攻击。

Birthday attack is a kind of common collision attack method,it can be used to attack any type of hash function.This paper first analyzes the principle of the algorithm of SHA-512,then discusses the collision threshold of the birthday attack as well as its attack steps,and at last makes an security analysis of SHA-512 algorithm under Birthday attack.By analyzing and after all the message blocks of SHA-512 algorithm have been dealt with,eight 64 bit variable data can be get from H0-H7 cascade can be got of which the output of the hash code is 512 bit,Therefore,it is unpredictable for the attacker,whose guessed probability can be ignored,while the computational complexity of finding the target message collision is 2256.So,relatively speaking,the security of SHA-512 is higher than MD5,SHA-1,and so on,it is more resistant to birthday attacks,and can resist known cryptanalytic attacks.