Section: Overall Objectives

Highlights of the Year

• Cryptanalysis of several recently proposed lightweight block ciphers: The area of lightweight primitives has drawn considerable attention over the last years, due to the need for low-cost cryptosystems for several emerging applications like RFID tags and sensor networks. The strong demand from industry has led to the design of a large number of lightweight block ciphers, with different implementation features. In this context, the need for a significant cryptanalysis effort is obvious. The demand from industry for clearly recommended lightweight ciphers requires that the large number of these potential candidates be narrowed down. In this context, the project-team has obtained cryptanalytic results on several recently proposed lightweight block ciphers, including an attack against the full cipher KLEIN-64, the best known attack against a round-reduced version of PRINCE, and some distinguishers on the internal permutation of LED.

• Cryptanalysis of a variant of the McEliece public-key cryptosystem based on some wild Goppa codes: The original McEliece cryptosystem proposed in 1978 uses the class of classical binary Goppa codes as private codes. Many other classes of codes have been suggested since the original proposal, but most of them have been cryptanalysed, while the class of Goppa codes still resists all structural attacks. Then, the use of a more general family of Goppa codes over ${𝐅}_q$, $q\ge 2$, named wild Goppa codes, has been proposed in 2010 by Bernstein et al. in order to reduce the key size of the system. Our recent work leads to an attack which allows to recover the private key in polynomial time when wild Goppa codes over a quadratic finite field extension are used. This is the very first structural attack of the McEliece cryptosystem when some Goppa codes are used. The key-point in the attack is the behaviour of these codes with respect to component-wise product of codes. A similar technique has also been exploited for breaking some other variants of the McEliece system, including one based on Reed-Solomon codes.

• Experimental demonstration of long-distance continuous-variable quantum key distribution: Distributing secret keys with information-theoretic security is arguably one of the most important achievements of the field of quantum information processing and communications. The rapid progress in this field has enabled quantum key distribution in real-world conditions and commercial devices are now readily available. Quantum key distribution systems based on continuous variables provide the major advantage that they only require standard telecommunication technology. However, to date, these systems have been considered unsuitable for long-distance communication. In collaboration with experimental groups, we have overcome all previous limitations and demonstrated for the first time continuous-variable quantum key distribution over 80 km of optical fibre. Our results correspond to an implementation guaranteeing the strongest level of security for quantum key distribution reported so far for such long distances and pave the way to practical applications of secure quantum communications.