Abstraction by Set-Membership:Verifying Security Protocols and Web Services with Databases

The abstraction and over-approximation of protocols and web services by a set of Horn clauses is a very successful method in practice. It has however limitations for proto-cols and web services that are based on databases of keys, contracts, or even access rights, where revocation is pos-sible, so that the set of true facts does not monotonically grow with state transitions. We extend the scope of these over-approximation methods by defining a new way of ab-straction that can handle such databases, and we formally prove that the abstraction is sound. We realize a translator from a convenient specification language to standard Horn clauses and use the verifier ProVerif and the theorem prover SPASS to solve them. We show by a number of examples that this approach is practically feasible for wide variety of verification problems of security protocols and web services

A reduced semantics for deciding trace equivalence using constraint systems

Many privacy-type properties of security protocols can be modelled using trace equivalence properties in suitable process algebras. It has been shown that such properties can be decided for interesting classes of finite processes (i.e., without replication) by means of symbolic execution and constraint solving. However, this does not suffice to obtain practical tools. Current prototypes suffer from a classical combinatorial explosion problem caused by the exploration of many interleavings in the behaviour of processes. M\"odersheim et al. have tackled this problem for reachability properties using partial order reduction techniques. We revisit their work, generalize it and adapt it for equivalence checking. We obtain an optimization in the form of a reduced symbolic semantics that eliminates redundant interleavings on the fly.Comment: Accepted for publication at POST'1

OFMC: A symbolic model checker for security protocols

We present the on-the-fly model checker OFMC, a tool that combines two ideas for analyzing security protocols based on lazy, demand-driven search. The first is the use of lazy data types as a simple way of building efficient on-the-fly model checkers for protocols with very large, or even infinite, state spaces. The second is the integration of symbolic techniques and optimizations for modeling a lazy Dolev-Yao intruder whose actions are generated in a demand-driven way. We present both techniques, along with optimizations and proofs of correctness and completeness. Our tool is state of the art in terms of both coverage and performance. For example, it finds all known attacks and discovers a new one in a test suite of 38 protocols from the Clark/Jacob library in a few seconds of CPU time for the entire suite. We also give examples demonstrating how our tool scales to, and finds errors in, large industrial-strength protocol

Automated Verification of Virtualized Infrastructures

Virtualized infrastructures and clouds present new challenges for security analysis and formal verification: they are complex environments that continuously change their shape, and that give rise to non-trivial security goals such as isolation and failure resilience requirements. We present a platform that connects declarative and expressive description languages with state-of-the art verification methods. The languages integrate homogeneously descriptions of virtualized infras-tructures, their transformations, their desired goals, and evaluation strategies. The different verification tools range from model checking to theorem proving; this allows us to exploit the complementary strengths of methods, and also to understand how to best represent the analysis problems in different contexts. We consider first the static case where the topology of the virtual infrastructure is fixed and demonstrate that our platform allows for the declarative specification of a large class of properties. Even though tools that are special-ized to checking particular properties perform better than our generic approach, we show with a real-world case study that our approach is practically feasible. We finally consider also the dynamic case where the intruder can actively change the topology (by migrating machines). The combination of a complex topology and changes to it by an intruder is a problem that lies beyond the scope of previous analysis tools and to which we can give first positive verification results