A strand is a sequence of events; it represents either an execution by a legitimate party in a security protocol or else a sequence of actions by a penetrator. A strand space is a collection of strands, equipped with a graph structure generated by causal interaction. In this framework, protocol correctness claims may be expressed in terms of the connections between strands of different kinds. P...

Cryptographic protocols are useful for trust engineering in distributed transactions. Transactions require specific degrees of confidentiality and agreement between the principals engaging in it. Moreover, trust management assertions may be attached to protocol actions, constraining the behavior of a principal to be compatible with its own trust policy. We embody these ideas in a cryptographic ...

In this paper we develop a framework, based on strand spaces, for reasoning about cryptographic protocols and characterizing their executions. We define skeletons, homomorphisms, and shapes. Skeletons model partial information about regular (honest) behavior in an execution of a cryptographic protocol. A homomorphism between skeletons is an information-preserving map. Much protocol analysis may...

A multi-party fair exchange protocol is a cryptographic protocol allowing several parties to exchange commodities in such a way that everyone gives an item away if and only if it receives an item in return. In this paper we discuss a multi-party fair exchange protocol originally proposed by Franklin and Tsudik, and subsequently shown to have flaws and fixed by González and Markowitch. We identi...

A guessing attack on a security protocol is an attack where an attacker guesses a poorly chosen secret (usually a low-entropy user password) and then seeks to verify that guess using other information. Past efforts to address guessing attacks in terms of design or analysis considered only protocols executed in isolation. However, security protocols are rarely executed in isolation and reality i...

There are still some shortcomings in the latest version of 5G authentication and key agreement (AKA) protocol, which is specified by third-generation partnership project (3GPP). To overcome these shortcomings, an improved primary protocol for networks (5G-IPAKA) were proposed. However, one AKA has not been completely 5G-IPAKA resulting denial service (DoS) attacks against both serving network (...