What is Grøstl?

Grøstl is a new cryptographic hash function designed in response to the Cryptographic Hash Algorithm Competition announced by NIST. Grøstl is one of the five finalists in the competition and it is a tweaked version of its predecessor called Grøstl-0, the original submission to the competition.

Grøstl is an iterated hash function, where the compression function is built from two fixed, large, different permutations. The design of Grøstl is transparent and based on principles very different from those used in the SHA-family.

The two permutations used are constructed using the wide trail design strategy, which makes it possible to give strong statements about the resistance of Grøstl against large classes of cryptanalytic attacks. Moreover, if these permutations are assumed to be ideal, there is a proof for the security of the hash function.

Grøstl is a byte-oriented SP-network which borrows components from the AES. The S-box used is identical to the one used in the block cipher AES and the diffusion layers are constructed in a similar manner to those of the AES. As a consequence there is a very strong confusion and diffusion in Grøstl.

Grøstl is a so-called wide-pipe construction where the size of the internal state is significantly larger than the size of the output. This has the effect that all known, generic attacks on the hash function are made much more difficult.

Grøstl has good performance on a wide range of different platforms, and counter-measures against side-channel attacks are well-understood from similar work on the AES.

It was designed by a team of cryptographers from Technical University of Denmark (DTU) and TU Graz.

About this webpage

This webpage is a companion to the submission and will serve as a place for distributing information on Grøstl.

If you have questions or comments, please write an e-mail to contact@groestl.info.