In this paper a simulation analysis of certain trust models (complex PKI architectures) with regard to the security support of B2B applications on the Internet is presented. The objective of such an analysis has been the choice of the most efficient PKI architecture and a solution of the cryptographic interoperability problem. A simulation model of protected B2B e-commerce has also been presented, based on the chosen PKI architecture. This paper has shown the significance of the up-to-date cryptographic mechanisms: digital signature and digital certificate to deliver the main security services based on PKI.