Implementation by the Keccak, Keyak and Ketje Teams, namely, Guido Bertoni,
Joan Daemen, Michaël Peeters, Gilles Van Assche and Ronny Van Keer, hereby
denoted as "the implementer".

For more information, feedback or questions, please refer to our websites:
http://keccak.noekeon.org/
http://keyak.noekeon.org/
http://ketje.noekeon.org/

To the extent possible under law, the implementer has waived all copyright
and related or neighboring rights to the source code in this file.
http://creativecommons.org/publicdomain/zero/1.0/

Ported to elm by Art Yerkes.

ethereum_keccak_256 is the hash function used in many places related to the
ethereum cryptocurrency.  It is different from sha3 in the padding used.

Elm 0.19 update by Coury Ditch
https://github.com/cmditch