Section: Scientific Foundations


Computer security has become more and more pressing as a concern since the mid 1990s. There are several reasons to this: cryptography is no longer a chasse réservée of the military, and has become ubiquitous; and computer networks (e.g., the Internet) have grown considerably and have generated numerous opportunities for attacks and misbehaviors, notably.

The aim of the SECSI project is to develop logic-based verification techniques for security properties of computer systems and networks. Let us explain what this means, and what this does not mean.

First, the scope of the research at SECSI started as a rather broad subset of computer security, although the core of SECSI's activities has always been on verifying cryptographic protocols.

We took this for granted in 2006, and decided to concentrate on the latter. This already includes a vast number of concerns.

First, there is a plethora of distinct security properties one may wish to verify. Beyond the standard properties of secrecy (weak or strong forms), or authentication, one considers anonymity, fairness in contract-signing, and the subtle security properties involved in electronic voting such as accountability, receipt-freeness, resistance to coercion, or user verifiability. Some of these properties are trace properties, some are not, and are therefore more complex to state and verify.

Second, there are many available models. SECSI started with the rather simple symbolic models of security known today as Dolev-Yao models. One must then look at process algebra models (spi-calculus, applied pi-calculus), which allow for a symbolic treatment of more complex properties, especially those that are not trace properties. And one must also look at the computational models favored by cryptographers, e.g., the game-based approaches and the universal composability/simulatability approaches. They are more realistic in terms of security, but less directly amenable to automated verification. One of the features of computational models that makes them more complex is the need for computing, and bounding probabilities of certain events. This led us into contributing to the field of verification of probabilistic systems. One must also look at the relations between these models.

Third, there are many important applications. While SECSI started looking at the rather simple and now mundane confidentiality and authentication protocols, two important application domains have emerged: the verification of electronic voting protocols, and the verification of cryptographic APIs.

Apart from cryptographic protocols, the initial vision of the SECSI project was that computer security, being a global concern, should be taken as a whole, as far as possible. This is why one of the initial objectives of SECSI included topic in intrusion detection, again seen from the logical point of view.

One should remember the following. First, one of the key phrases in the SECSI motto is “logic-based”. It is a founding theme of SECSI that logic matters in security, and opportunities are to be grabbed. Another key phrase is “verification techniques”. The expertise of SECSI is not in designing protocols or security architectures. Verifying protocols, formally, is an arduous task already, and has proved to be an extremely rich area.