## Cryptology ePrint Archive: Report 2007/165

Inductive Proof Method for Computational Secrecy

Arnab Roy and Anupam Datta and Ante Derek and John C. Mitchell

Abstract: We investigate inductive methods for proving secrecy properties of network protocols, in a computational" setting applying a probabilistic polynomial-time adversary. As in cryptographic studies, our secrecy properties assert that no probabilistic polynomial-time distinguisher can win a suitable game presented by a challenger. Our method for establishing secrecy properties uses inductive proofs of computational trace-based properties, and axioms and inference rules for relating trace-based properties to non-trace-based properties. We illustrate the method, which is formalized in a logical setting that does not require explicit reasoning about computational complexity, probability, or the possible actions of the attacker, by giving a modular proof of computational authentication and secrecy properties of the Kerberos V5 protocol.

Category / Keywords: cryptographic protocols /