加密模式与密码协议的安全性

Encrypt Mode and the Security of Cryptographic Protocol

密码协议的设计和安全性分析是困难的,在密码协议中总是以所使用的密码算法是安全的为前提,但是人们却忽略了密码算法的加密模式对密码协议安全性的影响。论文针对一个改进的Needham-Schroeder协议,假设其使用了分组密码的CBC加密模式,我们通过使用一条旧信息的明密文对来修改当前会话中的信息,从而成功地欺骗用户双方,并分别与他们建立了一个会话密钥,对该协议进行了成功的攻击。结果说明密码算法的加密模式对密码协议的安全性有着巨大的影响。

Design and analysis of secure cryptographic protocol is very difficult,we always suppose that the cryptographic algorithm which is used in cryptographic protocols is securely.We always ignore the effect of what kind of encrypt mode used by the cryptographic algorithm.Aiming at an amended Needham-schroeder protocol,we have supposed it uses DES as its encrypt algorithm and CBC mode as its encrypt mode.Through using an old message＇s ciphertext and plaintext to amend current message that an adversary successfully cheat both sides of user and agreed two new session keys with every sides of user,so the adversary can attack this protocol successfully.So we can drew the conclusion that the mode of the cryptographic algorithm can affect the security of cryptographic protocols seriously.