Electronic voting promises the possibility of a convenient, efficient and secure facility for recording and tallying votes in an election. Recently highlighted inadequacies of implemented systems have demonstrated the importance of formally verifying the underlying voting protocols. We study three privacy-type properties of electronic voting protocols: in increasing order of strength, they are ...

We propose a new specification framework for information hiding properties such as anonymity and privacy. The framework is based on the concept of a function view, which is a concise representation of the attacker’s partial knowledge about a function. We describe system behavior as a set of functions, and formalize different information hiding properties in terms of views of these functions. We...

We give a fully abstract game model for Idealized Algol with non-local control flow. In contrast to most previous papers on game semantics, we do not need to include the bad-variable constructor mkvar to obtain full abstraction. Using the model we show that, unlike in the “control-free” case, the presence of mkvar does affect observational equivalence. We conclude by discussing the effect of mk...

I study a problem of repeated moral hazard in which the effect of effort is persistent over time: each period’s outcome distribution is a function of a geometrically distributed lag of past efforts. I show that when the utility of the agent is linear in effort, a simple rearrangement of terms in his lifetime utility translates this problem into a related standard repeated moral hazard. The solu...

We present a timed process calculus for modelling wireless networks in which individualstations broadcast and receive messages; moreover the broadcasts are subject to collisions. Basedon a reduction semantics for the calculus we define a contextual equivalence to compare the externalbehaviour of such wireless networks. Further, we construct an extensional LTS (labelled transition<lb...

Theories of efficiency preorders and precongruences for concurrent systems have been described in various papers. We describe a procedure to implement two of these precongruences. Considering the extra information that is needed to be maintained while computing efficiency preorders, our procedure with a complexity O(nm), compares favourably with that for deciding observational equivalence (O(nm...

We generalize the linear rational expectations solution method of Whiteman (1983) to the multivariate case. This facilitates the use of a generic exogenous driving process that must only satisfy covariance stationarity. Multivariate cross-equation restrictions linking the Wold representation of the exogenous process to the endogenous variables of the rational expectations model are obtained. We...

A result on observational equivalence for PCF and innocent strategies, as presented at the Games for Logic and Programming Languages (GaLoP) workshop in York, March 2009. The full abstraction result for PCF using game semantics requires one to identify all innocent strategies that are innocently indistinguishable. This involves a quantification over all innocent tests, cf. quantification over a...

We define an observational equivalence for Lafont’s interaction combinators, which we prove to be the least discriminating non-trivial congruence on total nets (nets admitting a deadlock-free normal form) respecting reduction. More interestingly, this equivalence enjoys an internal separation property similar to that of Böhm’s Theorem for the λ-calculus.

The higher-order π-calculus is an extension of the π-calculus to allow communication of abstractions of processes rather than names alone. It has been studied intensively by Sangiorgi in his thesis where a characterisation of a contextual equivalence for higher-order π-calculus is provided using labelled transition systems and normal bisimulations. Unfortunately the proof technique used there r...