摘要: This paper describes the formal verification of the Merchant Registration phase of the Secure Electronic Transactions (SET) protocol, a realistic electronic transaction security protocol which is used to protect the secrecy of online purchases. A number of concepts, notations, functions, predicates, assumptions and rules are introduced. We describe the knowledge of all legal participants, and a malicious spy, to assess the security of the sub-protocol. Avoiding search in a large state space, the method converges very quickly. We implemented our method in the Isabelle/Isar automated reasoning environment, therefore the whole verification process can be executed mechanically and efficiently.