Group leader : Jean-Pierre TILLICH
The research work within the project-group is mostly devoted to the design and analysis of cryptographic algorithms, in the classical or in the quantum setting. It is especially motivated by the fact that the current situation of cryptography is rather fragile: many of the available symmetric and asymmetric primitives have been either threatened by recent progress in cryptanalysis or by the possible invention of a large quantum computer. Most of the work mixes fundamental aspects and practical aspects of information protection (cryptanalysis, design of algorithms, implementations).

Research themes

  • Symmetric cryptology: they focus on stream ciphers, block ciphers and hash functions. The group work considers all aspects of the field, from practical (new attacks, concrete specifications of new systems) to more theoretical ones (study of the algebraic structure of underlying mathematical objects, definition of optimal objects).
  • Code-based cryptography: Cryptographic primitives which exploit some problems coming from coding theory provide a good alternative to the commonly used systems based on number theory. They are usually named post-quantum cryptosystems since they would not become obsolete with the coming up of the quantum computer. They investigate the security of these systems, their practical implementation and the design of fast cryptographic primitives based on codes.
  • Reverse engineering of communication systems: When a communication is eavesdropped, some raw data, not necessarily encrypted, is observed out of a noisy channel. Then, to access the information, the whole communication system has first to be disassembled and every constituent reconstructed. They study this reverse engineering problem. Most notably, they investigate the problem of recovering the specifications of the involved scramblers and error-correcting codes.
  • Quantum information theory: The main obstacle towards the development of quantum computing is decoherence, a consequence of the interaction of the computer with a noisy environment. They investigate approaches to quantum error-correction as a way to fight against this effect, and they study more particularly some families of quantum error-correcting codes which generalise the best classical codes available today. Their research also covers quantum cryptography where they study the security of efficient protocols for key distribution, in collaboration with experimental groups. More generally, they investigate how quantum theory severely constraints the action of honest and malicious parties in cryptographic scenarios.