An extension of CS logic was proposed in this paper, which corrected some defects of CS logic, and extended the logic to analyze the symmetrical key cryptographic protocols.

• 该扩展逻辑对CS逻辑中存在的一些缺陷进行了修改和扩展，使其不仅可以分析公钥协议，还可以分析对称密钥协议。