A hash function is any function that can be used to map data of arbitrary size
to data of fixed size. A hash function usually has two main components: a permutation
function or compression function and mode of operation. We will propose a new concrete
novel design of a permutation based hash functions called Gear in this paper. It is a hash
function based on block cipher in Davies-Meyer mode. It uses the patched version of
Merkle-Damgård, i.e. the wide pipe construction as its mode of operation. Thus, the
intermediate chaining value has at least twice larger length than the output hash. And
the permutations functions used in Gear are inspired from the SHA-3 finalist Grøestl hash
function which is originally inspired from Rijndael design (AES). There is a very strong
confusion and diffusion in Gear as a result
