From the Keccak website:
Keccak is a family of sponge functions. The sponge function is a generalization of the concept of cryptographic hash function with infinite output and can perform quasi all symmetric cryptographic functions, from hashing to pseudo-random number generation to authenticated encryption.
cykeccak is a thin Cython wrapper around the reference implementation of
Keccak and an implementation of SHA-3
on top of that wrapper.
Cython is not required to build cykeccak as long as the source distribution
contains a keccak.c file, such as the tarballs available from pypi. Installing from a github tarball is
not recommended, as they ship without keccak.c, version.txt, or a
.git directory. With neither version.txt nor a git repository present,
setup.py will be unable to determine the version of cykeccak.
The underlying C code is architechture-dependent, and setup.py will attempt
to guess whether to build from the 32-bit or 64-bit sources based on whether
the python executing setup.py is a 32- or 64-bit binary. To avoid guessing,
the CYKECCAK_IMPLEMENTATION environment variable can also be set to either
opt32 or opt64.