The calculation of session key groups and the verifying of parameters 'correctness are done by simple bit operation on the basis of completing identity authentication, and the asynchronous attack can be resisted by dynamically switching the parameter of the protection keys. 协议在完成身份认证的基础上,会话密钥组的计算与参数的正确性确认均采用简单的位运算,并且通过参保密钥的动态切换可以抵抗非同步攻击。