Exploring Fair Exchange Protocols Using Specification Animation

On the security of fair non-repudiation protocols

“…One protocol was proposed by Zhou et al [25,26] and has already been analyzed and improved in [9]. The second protocol is a very similar one proposed by Kremer and Markowitch [14,17].…”

“…After defining fair non-repudiation with timeliness we demonstrate attacks on two protocols for efficient fair nonrepudiation with timeliness. Some of these attacks are related to previously published ones [9,13]. Next, the design weaknesses enabling the attacks are discussed, and design principles to avoid these known attacks are proposed.…”

An Application of Justification Logic to Protocol Verification

“…As already mentioned in the introduction, there are several attacks known on this kind of protocols [9], [10]. So, what is wrong with our analysis?…”

“…However, the problem is that we have to guarantee that a concrete implementation satisfies the (implicit) assumptions of our formalization. For instance, axiom (9) states that the recipient sends a receipt R after seeing the commitment C. In our formalization, there is no connection between R and C. So when A presents R to the judge to prove that she said a certain message, we implicitly assume that R and C match to the same message. A concrete implementation of the protocol has to guarantee this connection of R and C which is one of the attack points that has been exploited and that has to be addressed in a future extension of our logic.…”

“…Zhou and Gollmann [6] already provide a formal analysis of their protocol using a BAN [7] like logic, the SVO logic [8] to specify and verify NRO and NRR. Today, there are many variants of this protocol available and also there are several attacks known on this kind of protocols, see for instance [9], [10].…”