Computational Soundness of Formal Encryption in Coq

We formalize Abadi and Rogaway's computational soundness result in the Coq interactive theorem prover. This requires to model notions of provable cryptography like indistinguishability between ensembles of probability distributions, PPT reductions, and security notions for encryption schemes. Our formalization is the first computational soundness result to be mechanized, and it shows the feasibility of rigorous reasoning of computational cryptography inside a generic interactive theorem prover

Modeling Adversaries in a Logic for Security Protocol Analysis

Logics for security protocol analysis require the formalization of an adversary model that specifies the capabilities of adversaries. A common model is the Dolev-Yao model, which considers only adversaries that can compose and replay messages, and decipher them with known keys. The Dolev-Yao model is a useful abstraction, but it suffers from some drawbacks: it cannot handle the adversary knowing protocol-specific information, and it cannot handle probabilistic notions, such as the adversary attempting to guess the keys. We show how we can analyze security protocols under different adversary models by using a logic with a notion of algorithmic knowledge. Roughly speaking, adversaries are assumed to use algorithms to compute their knowledge; adversary capabilities are captured by suitable restrictions on the algorithms used. We show how we can model the standard Dolev-Yao adversary in this setting, and how we can capture more general capabilities including protocol-specific knowledge and guesses.Comment: 23 pages. A preliminary version appeared in the proceedings of FaSec'0