Section: Scientific Foundations

What is computer security? Do we need some?

This section is unchanged from the SECSI 2006 report.

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 is a rather broad subset of computer security, although the core of SECSI's activities is on verifying cryptographic protocols. The SECSI group has tried to be as comprehensive as possible. Several security properties have been the focus of SECSI's research: weak and strong secrecy, authentication, anonymity, fairness in contract-signing notably. Several models, too: the Dolev-Yao model initially, but also process algebra models (spi-calcul, applied pi-calculus), and, more recently, the more realistic computational models favored by cryptographers. Several input formats, finally: either symbolic descriptions of protocols à la Needham-Schroeder, or programs that actually implement cryptographic protocols.

Apart from cryptographic protocols, the vision of the SECSI project is 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 was also concerned with problems in intrusion detection, notably.

However, the aims of any project, including SECSI, have to be circumscribed somewhat. One of the key points in the aim of the SECSI project, stated above, is “logic-based”. SECSI aims at developing rigorous approaches to the verification of security. But the expertise of the members of SECSI are not in, say, numerical analysis or the quantitative evaluation of degrees of security, but in formal methods in logic. It is a founding theme of SECSI that logic matters in security, and opportunities are to be grabbed. This was definitely the case for the verification of cryptographic protocols. This was also the case for intrusion detection, where an original model-checking based approach to misuse detection was developed.

Then, another important point is “verification techniques”. The expertise of SECSI is not so much in designing protocols. Verifying protocols, formally, is a rather more arduous task. It is also particularly needed in cryptographic protocol security, where many protocols were flawed, despite published proofs.

Automated cryptographic protocol verification is certainly the main theme of SECSI. While it was already the theme that kept most SECSI members busy at the time SECSI was created (2002), one might say that, as of 2006, all SECSI members work on it. Accordingly, this theme was naturally subdivided into new objectives.

1. Tree-automata based methods, automated deduction, and approximate/exact cryptographic protocol verification in the Dolev-Yao model.

2. Enriching the Dolev-Yao model with algebraic theories, and associated decision problems.

3. Computational soundness of formal models (Dolev-Yao, applied pi-calculus).

4. Indistinguishability proofs allowing us to handle more properties, e.g. anonymity.

5. Application to new security protocols, e.g. electonic voting protocols.

6. Security in the presence of probabilistic and demonic non-deterministic choices.