Section: Application Domains

Hash Functions

Since the previous section just ended on this topic, we start with it for the major problems to address within the next 5 years. A NIST competition on hash functions has been launched late 2007. In the first step, cryptographers had to build and analyze their own candidate; in a second step, cryptanalysts are solicited, in order to analyze and break all the proposals. The conclusion is planned for 2012.

The symmetric people of the Cascade team have worked this year on the development of a new hash function called SIMD that has been selected for the second round of the NIST SHA-3 competition. SIMD hash function is quite similar to members of the MD/SHA family. It is based on a familiar Merkle-Damgard design, where the compression function is built from a Feistel-like cipher in Davies-Meyer mode. However there are some innovations in this design: the internal state is twice as big as the output size, we use a strong message expansion, and we use a modified feed-forward in the compression function. The main design criteria was to follow the MD/SHA designs principle which are quite well understood, and to add some elements to avoid all known attacks. SIMD is particularly efficient on platforms with vector instructions (SIMD) which are available on many processors. Such instructions have been proposed since 1997 and are now widely deployed. Moreover, it is also possible to use two cores on multicore processors to boost the performances with a factor 1.8 by splitting the message expansion function and the hashing process.

We've also drawn some analyses and attacks on the other candidates.