  Based on our previous work on truly concurrent process algebras APTC, we use
it to verify the security protocols. This work (called Secure APTC, abbreviated
SAPTC) have the following advantages in verifying security protocols: (1) It
has a firmly theoretic foundations, including equational logics, structured
operational semantics, and axiomatizations between them; (2) It has rich
expressive powers to describe security protocols. Cryptographic operations are
modeled as atomic actions and can be extended, explicit parallelism and
communication mechanism to modeling communication operations and principals,
rich computational properties to describing computational logics in the
security protocols, including conditional guards, alternative composition,
sequential composition, parallelism and communication, encapsulation and
deadlock, recursion, abstraction. (3) Especially by abstraction, it is
convenient and obvious to observe the relations between the inputs and outputs
of a security protocols, including the relations without any attack, the
relations under each known attack, and the relations under unknown attacks if
the unknown attacks can be described.
