CRUNCHA candidate for the NIST hash competition (SHA3)
TeamSubmitter: Jacques Patarin (PRISM, University of Versailles Saint Quentin, France) Team: Louis Goubin (PRISM, UVSQ)
 Mickael Ivascot (PRISM, UVSQ)
 William Jalby (PRISM, UVSQ)
 Olivier Ly (LABRI, Bordeaux University, France)
 Valerie Nachef (University of CergyPontoise, France)
 Joana Treger (UVSQ)
 Emmanuel Volte (UCP)
 PresentationThe
algorithm enables to obtain digests of 224, 256, 384 and 512 bits.
First an encryption permutation based on an unbalanced Feistel scheme
with expanding functions will be designed.
This permutation will be a pseudorandom permutation from kn bits to kn bits using random expanding functions from n bits to (k1)n
bits. Then a compression function is constructed by xoring two such
permutations and choosing a number of bits depending on the desired
length of the message digest.
The hash algorithm can be
described in four stages: preprocessing, encryption permutation,
compression function and hash computations. Preprocessing
involves padding the message, setting an initialization vector and an
initial value. The hash computation uses 2 encryption permutations, the
compression function together with the MerkleDamgard construction.
The
proposed hash algorithm (CRUNCH) has an extremely simple structure:
basically the innermost loop amounts to accessing Sboxes and XORing
the data accessed. Its simplicity is key to our design because it
allows simple and efficient implementation on almost any
microprocessor, it simplifies its protection and finally it makes
easier to establish a direct relation between CRUNCH security and a
generic (well known) security problem. The simplicity of its
computational structure is compensated by the requirement of accessing
(and storing) Sboxes hose total size is around 1 MB. This
storage requirement can be lifted by computing on the fly the Sboxes.
Although it increases the computational requirements, it does not alter
any properties on the security of CRUNCH.

Download Specifications: crunch_specifications.pdf (last change 27/01/2009)
Slides presentation: crunch_presentation.pdf
New release package (7/02/2009) : rar (15MB) or directory

Comments, news
Use of the double pipe version of CRUNCH with another cipher: Katan (2012)
Here a version of crunch_256 of about 10KB (in 32 bits or 64 bits). The constants are calculated on the fly.
Contact: emmanuel.volte@aliceadsl.fr 
