Ongoing Research Areas in Symmetric Cryptography

Project co-funded by the European Commission within the 6th Framework Programme Dissemination Level PU Public X PP Restricted to other programme participants (including the Commission services) RE Restricted to a group specified by the consortium (including the Commission services) CO Confidential, only for members of the consortium (including the Commission services) The information in this document is provided as is, and no warranty is given or implied that the information is fit for any particular purpose. The user thereof uses the information at its sole risk and liability. Basic cryptographic algorithms split into two families: symmetric algorithms, otherwise known as secret-key algorithms, which normally require a key to be shared and simultaneously kept secret within a restricted group, and public-key algorithms where the private key is almost never shared. From outside, this may give the impression that symmetric techniques become obsolete after the invention of public-key cryptography in the mid 1970's. However, symmetric techniques are still widely used because they are the only ones that can achieve some major functionalities as high-speed or low-cost encryption, fast authentication, and efficient hashing. Today, we find symmetric algorithms in GSM mobile phones, in credit cards, in WLAN connections, and symmetric cryptology is a very active research area. There is a strong need for further research in this area. On the one hand, new industrial needs are arising with the development of new application environments. For instance, the demand for low-cost primitives dedicated to low-power devices is pressing. On the other hand, progress in cryptanalysis may threaten the security of some existing and widely used algorithms. A better understanding of recent attacks is then necessary for the evaluation of existing primitives and for designing new and more secure ones. This report gives a brief summary of some of the research trends in symmetric cryptography at the time of writing, and the present report is the final version (revision of Y4). The following aspects of symmetric cryptography are investigated in this report: • the status of work with regards to different types of symmetric algorithms, including block ciphers, stream ciphers, hash functions and MAC algorithms (Section 1); • the algebraic attacks on symmetric primitives (Section 2); • the design criteria for symmetric ciphers (Section 3); • the provable properties of symmetric primitives (Section 4); • the major industrial needs in the area of symmetric cryptography (Section 5). Four major aspects have been identified and were …