Judicaël Courant

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Chosen-ciphertext security is by now a standard security property for asymmetric encryption. Many generic constructions for building secure cryptosystems from primitives with lower level of security have been proposed. Providing security proofs has also become standard practice. There is, however, a lack of automated verification procedures that analyze(More)
Several proof-assistants rely on the very formal basis of Pure Type Systems (PTS) as their foundations. We are concerned with the issues involved in the development of large proofs in these provers such as namespace management, development of reusable proof libraries and separate verification. Although implementations offer many features to address them,(More)
The SML-like module systems are small typed languages of their own. As is, one would expect a proof of their soundness following from a proof of subject reduction. Unfortunately, the subject-reduction property and the preservation of type abstraction seem to be incompatible. As a consequence, in relevant module systems, the theoretical study of reductions(More)
Type systems for secure information flow aim to prevent a program from leaking information from variables that hold secret data to variables that hold public data. In this work we present a type system to address deterministic encryption. The intuition that encrypting a secret yields a public value, that can be stored in a public variable, is faithful for(More)
Chosen-ciphertext security is by now a standard security property for asymmetric encryption. Many generic constructions for building secure cryptosystems from primitives with lower level of security have been proposed. Providing security proofs has also become standard practice. There is, however, a lack of automated verification procedures that analyse(More)
This paper presents a new lambda-calculus with singleton types, called λ βδ ≤{}. The main novelty of λ βδ ≤{} is the introduction of a new reduction, the δ-reduction, replacing any variable declared of singleton type by its value, and the definition of equality as the syntactic equality of βδ-normal forms. The δ-reduction has a very odd behavior on untyped(More)
We study a normalization function in an algebra of terms quotiented by an associa-tive, commutative and involutive operator (logical xor). This study is motivated by the formal verification of cryptographic systems, where a normalization function for xor-terms turns out to play a key role. Such a function is easy to define using general recursion. However,(More)