Based on comprehensive analysis on security requirements of information transmission, security primitive is generated by automatic tool in asymmetric key cryptosystem, and improved with addition of compositional factors. And then, formal processes of secure information transmission are constructed with composition method. Formal analysis shows that, secrecy, integrity, availability, controllability, non-repudiation and identifiability during information transmission can be insured by this architecture, as a common framework for development of various application systems in digital campus from the viewpoint of information security.