Sound Computational Interpretation of Formal Encryption with Composed Keys

The formal and computational views of cryptography have been related by the seminal work of Abadi and Rogaway. In their work, a formal treatment of encryption that uses atomic keys is justified in the computational world. However, many proposed formal approaches allow the use of composed keys, where any arbitrary expression can be used as encryption key. We consider an extension of the formal model presented by Abadi and Rogaway, in which it is allowed to use composed keys in formal encryption. We then provide a computational interpretation for expressions that allow us to establish the computational soundness of formal encryption with composed keys

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

Analysis models for security protocols

In this thesis, we present five significant, orthogonal extensions to the Dolev Yao model. Each extension considers a more realistic setting, closer to the real world, thus providing a stronger security guarantee. We provide examples both from the literature and from industrial case studies to show the practical applicability of each extension

Crypto-Verifying Protocol Implementations in ML

We intend to narrow the gap between concrete implementations and verified models of cryptographic protocols. We consider protocols implemented in F#, a variant of ML, and verified using CryptoVerif, Blanchet's protocol verifier for computational cryptography. We experiment with compilers from F# code to CryptoVerif processes, and from CryptoVerif declarations to F# code. We present two case studies: an implementation of the Otway-Rees protocol, and an implementation of a simplified password-based authentication protocol. In both cases, we obtain concrete security guarantees for a computational model closely related to executable code

A Logic for Constraint-based Security Protocol Analysis

We propose PS-LTL, a pure-past security linear temporal logic that allows the specification of a variety of authentication, secrecy and data freshness properties. Furthermore, we present a sound and complete decision procedure to establish the validity of security properties for symbolic execution traces, and show the integration with constraint-based analysis techniques

An Audit Logic for Accountability

We describe and implement a policy language. In our system, agents can distribute data along with usage policies in a decentralized architecture. Our language supports the specification of conditions and obligations, and also the possibility to refine policies. In our framework, the compliance with usage policies is not actively enforced. However, agents are accountable for their actions, and may be audited by an authority requiring justifications.Comment: To appear in Proceedings of IEEE Policy 200

Security Analysis of Parlay/OSA Framework

This paper analyzes the security of the Trust and Security Management (TSM) protocol, an authentication protocol which is part of the Parlay/OSA Application Program Interfaces (APIs). Architectures based on Parlay/OSA APIs allow third party service providers to develop new services that can access, in a controlled and secure way, to those network capabilities offered by the network operator. Role of the TSM protocol, run by network gateways, is to authenticate the client applications trying to access and use the network capabilities features offered. For this reason potential security flaws in its authentication strategy can bring to unauthorized use of network with evident damages to the operator and to the quality of the services. This paper shows how a rigorous formal analysis of TSM underlines serious weaknesses in the model describing its authentication procedure. This usually means that also the original system (i.e., the TSM protocol itself) hides the same flaws. The paper relates about the design activity of the formal model, the tool-aided verification performed and the security flaws discovered. This will allow us to discuss about how the security of the TSM protocol can be generally improve

A Protocol Compiler for Secure Sessions in ML

Distributed applications can be structured using sessions that specify flows of messages between roles. We design a small specific language to declare sessions. We then build a compiler, called s2ml, that transforms these declarations down to ML modules securely implementing the sessions. Every run of a well-typed program executing a session through its generated module is guaranteed to follow the session specification, despite any low-level attempt by coalitions of remote peers to deviate from their roles. We detail the inner workings of our compiler, along with our design choices, and illustrate the usage of s2ml with two examples: a simple remote procedure call session, and a complex session for a conference management system

Computational Secrecy by Typing for the Pi Calculus

We define and study a distributed cryptographic implementation for an asynchronous pi calculus. At the source level, we adapt simple type systems designed for establishing formal secrecy properties. We show that those secrecy properties have counterparts in the implementation, not formally but at the level of bitstrings, and with respect to probabilistic polynomial-time active adversaries. We rely on compilation to a typed intermediate language with a fixed scheduling strategy. While we exploit interesting, previous theorems for that intermediate language, our result appears to be the first computational soundness theorem for a standard process calculus with mobile channels