6HAIDAR A N, ABDALLAH A E. Formal Modelling of PKI Based Authentication [J]. Electronic Notes in Theo- retical Computer Science, 2009, 235:55 -70.
7ALTERMAN Peter. The U. S. Federal PKI and the Feder- al Bridge Certification Federal Bridge Certification Au- thority [J]. Computer Networks, 2001, 36 ( 6 ) : 685 -690.