A novel formal logic for formal analysis of timeliness in non-repudiation protocols

Abstract

Non-repudiation protocols are aimed at exchanging digital messages and irrefutable receipts between two mistrusting parties over the Internet, which form the cornerstones of modern secure network transactions. Timeliness is a key security property of non-repudiation protocols, which ensures that protocol agents can terminate their execution within a finite time, and guarantees the satisfaction of time-constraint among protocol events. A number of analysis methods have been proposed, but most of them cannot explicitly express the time factor which plays an important role in protocols. In order to address the challenge of analyzing timeliness, this paper extends the logic of events theory (LoET) and proposes a novel formal logic. By explicitly introducing the time factor into predicate formulas, the new logic can model actions, knowledge, and process states of each agent at different time points, thus enhancing its ability of time description. The formal semantics of new logic is given to avoid ambiguity of logic language and guarantee the soundness of new logic. A typical non-repudiation protocol is analyzed with new logic, and the timeliness flaw is discovered. The proposed logic overcomes the limitations of LoET in terms of time description and effectively addresses the issue of the inability to analyze timeliness.