In this paper, a cryptographic protocol together with its cryptographic algorithms is regarded as one system, and a security model for the system is built. Based on assume-guarantee compositional reasoning techniques, a new assume-guarantee based reasoning rule and algorithm are proposed, and the soundness of the rule is proved. In realizing model checking to the cryptographic protocol system, several difficulties are solved chiefly such as decomposition of the system, generation of assumed functions, and specifying security properties in forms of both logic formulas and processes. Using this security model and assume-guarantee based reasoning techniques, the kerberos cryptographic protocol system is verified.%将密码协议与密码算法视为一个系统,建立了密码协议系统的一种安全模型.基于假设/保证的组合推理技术提出了新的假设/保证推理规则和假设/保证推理算法,证明了该规则的完备性,实现了密码协议系统的模型检查,并重点解决了系统分解问题、假设函数的设定问题、进程+逻辑的系统特性描述问题等难题.以kerberos密码协议系统为例,利用该安全模型和假设/保证推理技术对密码协议系统进行了安全验证.
展开▼