Epistemic logic, Cryptography, Logical Omniscience, BAN Logic
2005 (English)Conference paper (Refereed)
BAN logic is an epistemic logic for verifying cryptographic protocols. While BAN has been quite successful from a practical point of view, the semantics of the epistemic modality is unclear. Several Kripke semantics have been proposed, but they do not attempt at anything beyond a soundness result. Completeness is prevented by the so called logical omniscience problem: Agents in BAN can draw only feasibly computable consequences of their knowledge, whereas agents in Kripke semantics are not so constrained. To circumvent this problem, we index the epistemic possibility relation of Kripke semantics with a message renaming, relating how cipher texts at the current state correspond to cipher texts at the epistemically possible state. An agent is said to know a property of a message if corresponding messages at epistemically possible states satisfy that property. We obtain completeness with respect to message passing systems, and decidability, by transferring canonical model and filtration constructions from Kripke semantics.
Place, publisher, year, edition, pages
Epistemic logic, Cryptography, Logical Omniscience, BAN Logic, Completeness
Computer and Information Science
IdentifiersURN: urn:nbn:se:kth:diva-62961OAI: oai:DiVA.org:kth-62961DiVA: diva2:481436
Methods for Modalities (M4M)