On convergence-sensitive bisimulation and the embedding of CCS in timed CCS

We propose a notion of convergence-sensitive bisimulation that is built just over the notions of (internal) reduction and of (static) context. In the framework of timed CCS, we characterise this notion of `contextual' bisimulation via the usual labelled transition system. We also remark that it provides a suitable semantic framework for a fully abstract embedding of untimed processes into timed ones. Finally, we show that the notion can be refined to include sensitivity to divergence

On the Decidability of Fragments of the Asynchronous Pi-Calculus

We study the decidability of a reachability problem for various fragments of the asynchronous $\pi$-calculus. We consider the combination of three main features: name generation, name mobility, and unbounded control. We show that the combination of name generation with either name mobility or unbounded control leads to an undecidable fragment. On the other hand, we prove that name generation without name mobility and with bounded control is decidable by reduction to the coverability problem for Petri Nets

On the Reachability Problem in Cryptographic Protocols

We study the verification of secrecy and authenticity properties for cryptogra- phic protocols which rely on symmetric shared keys. The verification can be reduced to check whether a certain parallel program which models the protocol and the specification can reach an erroneous state while interacting with the environment. Assuming finite principals, we present a simple decision procedure for the reachability problem which is based on a symbolic' reduction system

Certifying cost annotations in compilers

We discuss the problem of building a compiler which can lift in a provably correct way pieces of information on the execution cost of the object code to cost annotations on the source code. To this end, we need a clear and flexible picture of: (i) the meaning of cost annotations, (ii) the method to prove them sound and precise, and (iii) the way such proofs can be composed. We propose a so-called labelling approach to these three questions. As a first step, we examine its application to a toy compiler. This formal study suggests that the labelling approach has good compositionality and scalability properties. In order to provide further evidence for this claim, we report our successful experience in implementing and testing the labelling approach on top of a prototype compiler written in OCAML for (a large fragment of) the C language

An Elementary affine λ-calculus with multithreading and side effects (extended version)

Linear logic provides a framework to control the complexity of higher-order functional programs. We present an extension of this framework to programs with multithreading and side effects focusing on the case of elementary time. Our main contributions are as follows. First, we provide a new combinatorial proof of termination in elementary time for the functional case. Second, we develop an extension of the approach to a call-by-value $lambda$-calculus with multithreading and side effects. Third, we introduce an elementary affine type system that guarantees the standard subject reduction and progress properties. Finally, we illustrate the programming of iterative functions with side effects in the presented formalism

On the decidability of fragments of the asynchronous π-calculus

AbstractWe study the decidability of a reachability problem for various fragments of the asynchronous π-calculus. We consider the combination of three main features: name generation, name mobility, and unbounded control. We show that the combination of name generation with either name mobility or unbounded control leads to an undecidable fragment. On the other hand, we prove that name generation without name mobility and with bounded control is decidable by reduction to the coverability problem for Petri Nets

Certifying and reasoning about cost annotations of functional programs

We present a so-called labelling method to insert cost annotations in a higher-order functional program, to certify their correctness with respect to a standard compilation chain to assembly code including safe memory management, and to reason on them in a higher-order Hoare logic.Comment: Higher-Order and Symbolic Computation (2013

The Receptive Distributed π\pi-Calculus

In this paper we study an asynchronous distributed $\pi$-calculus, with constructs for localities and migration. We show that a simple static analysis ensures the receptiveness of channel names, which, together with a simple type system, guarantees a local deadlock-freedom property, that we call message deliverability. This property states that any migrating message will find an appropriate receiver at its destination locality. We argue that this distributed, receptive calculus is still expressive enough, by giving a series of examples illustrating the «receptive style» of programming we have. Finally we show that our calculus contains the $\pi_1$-calculus, up to weak asynchronous bisimulation

On the Symbolic Reduction of Processes with Cryptographic Functions

We study the reachability problem for cryptographic protocols represented as processes relying on perfect cryptographic functions. We introduce a symbolic reduction system that can handle hashing functions, symmetric keys, and public keys. Desirable properties such as secrecy or authenticity are specified by inserting logical assertions in the processes. We show that the symbolic reduction system provides a flexible decision procedure for finite processes and a reference for sound implementations. The symbolic reduction system can be regarded as a variant of syntactic unification which is compatible with certain set-membership constraints. For a significant fragment of our formalism, we argue that a dag implementation of the symbolic reduction system leads to an algorithm running in NPTIME thus matching the lower bound of the problem. In the case of iterated or finite control processes, we show that the problem is undecidable in general and in NPTIME for a subclass of iterated processes that do not rely on pairing. Our technique is based on rational transductions of regular languages and it applies to a class of processes containing the ping-pong protocols presented in [DolevEK-IC82]