Prototyping Formal System Models with Active Objects

We propose active object languages as a development tool for formal system models of distributed systems. Additionally to a formalization based on a term rewriting system, we use established Software Engineering concepts, including software product lines and object orientation that come with extensive tool support. We illustrate our modeling approach by prototyping a weak memory model. The resulting executable model is modular and has clear interfaces between communicating participants through object-oriented modeling. Relaxations of the basic memory model are expressed as self-contained variants of a software product line. As a modeling language we use the formal active object language ABS which comes with an extensive tool set. This permits rapid formalization of core ideas, early validity checks in terms of formal invariant proofs, and debugging support by executing test runs. Hence, our approach supports the prototyping of formal system models with early feedback.Comment: In Proceedings ICE 2018, arXiv:1810.0205

Verifying Privacy-Type Properties in a Modular Way

Formal methods have proved their usefulness for analysing the security of protocols. In this setting, privacy-type security properties (e.g. vote-privacy, anonymity, unlink ability) that play an important role in many modern applications are formalised using a notion of equivalence. In this paper, we study the notion of trace equivalence and we show how to establish such an equivalence relation in a modular way. It is well-known that composition works well when the processes do not share secrets. However, there is no result allowing us to compose processes that rely on some shared secrets such as long term keys. We show that composition works even when the processes share secrets provided that they satisfy some reasonable conditions. Our composition result allows us to prove various equivalence-based properties in a modular way, and works in a quite general setting. In particular, we consider arbitrary cryptographic primitives and processes that use non-trivial else branches. As an example, we consider the ICAO e-passport standard, and we show how the privacy guarantees of the whole application can be derived from the privacy guarantees of its sub-protocols

Composing security protocols: from confidentiality to privacy

Security protocols are used in many of our daily-life applications, and our privacy largely depends on their design. Formal verification techniques have proved their usefulness to analyse these protocols, but they become so complex that modular techniques have to be developed. We propose several results to safely compose security protocols. We consider arbitrary primitives modeled using an equational theory, and a rich process algebra close to the applied pi calculus. Relying on these composition results, we derive some security properties on a protocol from the security analysis performed on each of its sub-protocols individually. We consider parallel composition and the case of key-exchange protocols. Our results apply to deal with confidentiality but also privacy-type properties (e.g. anonymity) expressed using a notion of equivalence. We illustrate the usefulness of our composition results on protocols from the 3G phone application and electronic passport

A standard-driven communication protocol for disconnected clinics in rural areas

The importance of the Electronic Health Record (EHR), which stores all healthcare-related data belonging to a patient, has been recognized in recent years by governments, institutions, and industry. Initiatives like Integrating the Healthcare Enterprise (IHE) have been developed for the definition of standard methodologies for secure and interoperable EHR exchanges among clinics and hospitals. Using the requisites specified by these initiatives, many large-scale projects have been set up to enable healthcare professionals to handle patients' EHRs. Applications deployed in these settings are often considered safety-critical, thus ensuring such security properties as confidentiality, authentication, and authorization is crucial for their success. In this paper, we propose a communication protocol, based on the IHE specifications, for authenticating healthcare professionals and assuring patients' safety in settings where no network connection is available, such as in rural areas of some developing countries. We define a specific threat model, driven by the experience of use cases covered by international projects, and prove that an intruder cannot cause damages to the safety of patients and their data by performing any of the attacks falling within this threat model. To demonstrate the feasibility and effectiveness of our protocol, we have fully implemented it

An Integrated Environment for Efficient Formal Design and Verification

The general goal of this project was to improve the practicality of formal methods by combining techniques from model checking and theorem proving. At the time the project was proposed, the model checking and theorem proving communities were applying different tools to similar problems, but there was not much cross-fertilization. This project involved a group from SRI that had substantial experience in the development and application of theorem-proving technology, and a group at Stanford that specialized in model checking techniques. Now, over five years after the proposal was submitted, there are many research groups working on combining theorem-proving and model checking techniques, and much more communication between the model checking and theorem proving research communities. This project contributed significantly to this research trend. The research work under this project covered a variety of topics: new theory and algorithms; prototype tools; verification methodology; and applications to problems in particular domains

Automating Deductive Verification for Weak-Memory Programs

Writing correct programs for weak memory models such as the C11 memory model is challenging because of the weak consistency guarantees these models provide. The first program logics for the verification of such programs have recently been proposed, but their usage has been limited thus far to manual proofs. Automating proofs in these logics via first-order solvers is non-trivial, due to reasoning features such as higher-order assertions, modalities and rich permission resources. In this paper, we provide the first implementation of a weak memory program logic using existing deductive verification tools. We tackle three recent program logics: Relaxed Separation Logic and two forms of Fenced Separation Logic, and show how these can be encoded using the Viper verification infrastructure. In doing so, we illustrate several novel encoding techniques which could be employed for other logics. Our work is implemented, and has been evaluated on examples from existing papers as well as the Facebook open-source Folly library.Comment: Extended version of TACAS 2018 publicatio