• skerl ** Overview =skerl= is a NIF wrapper around Skein hashing functions

** Quick Start You must have [[http://erlang.org/download.html][Erlang/OTP R13B04]] or later and a GNU-style build system to compile and run =skerl=.

+BEGIN_SRC shell

git clone git://github.com/basho/skerl.git cd skerl make

+END_SRC

Start up an Erlang shell with the path to =skerl= included.

+BEGIN_SRC shell

cd path/to/skerl/ebin erl

+END_SRC

Hash a binary by calling =skerl:hash/2= with the desired number of bits for the resulting hash:

+BEGIN_SRC erlang

1> Bits = 256. 256 2> Data = <<"foobarbazquux">>. <<"foobarbazquux">> 3> {ok, Hash} = skerl:hash(Bits, Data). {ok,<<206,36,175,108,168,91,124,11,181,108,144,164,36, 216,130,110,241,197,98,180,65,120,56,225,1,255,54, ...>>} 4> bit_size(Hash). 256

+END_SRC

You may find =skerl:hexhash/2= more useful, as it returns a hexadecimal-encoded string representing the hash:

+BEGIN_SRC erlang

5> HexHash = skerl:hexhash(Bits, Data).
<<"ce24af6ca85b7c0bb56c90a424d8826ef1c562b4417838e101ff3627dcc000bc">>

+END_SRC

** The Skein Hash

The underlying hashing code in Skerl is the reference implementation of Skein from the official NIST submission.

Skein is a [[http://csrc.nist.gov/groups/ST/hash/sha-3/Round3/submissions_rnd3.html][finalist candidate in the NIST competition to become SHA-3]].

It is a hash function designed by Niels Ferguson, Stefan Lucks, Bruce Schneier, Doug Whiting, Mihir Bellare, Tadayoshi Kohno, Jon Callas, and Jesse Walker.

Details on the algorithm as submitted and known analysis can be found at [[http://ehash.iaik.tugraz.at/wiki/Skein][ecrypt]].

A [[http://www.schneier.com/skein1.3.pdf][full paper on Skein]] by the designers has been published.

The [[http://www.skein-hash.info/][official Skein page]] uses the headline:

Fast, Secure, Simple, Flexible, Efficient. And it rhymes with "rain."

** Contributing We encourage contributions to =skerl= from the community.

1. Fork the =skerl= repository on [[https://github.com/basho/skerl][Github]].
2. Clone your fork or add the remote if you already have a clone of the repository.

   +BEGIN_SRC shell

   git clone [email protected]:yourusername/skerl.git

   or

   git remote add mine [email protected]:yourusername/skerl.git

   +END_SRC

3. Create a topic branch for your change.

   +BEGIN_SRC shell

   git checkout -b some-topic-branch

   +END_SRC

4. Make your change and commit. Use a clear and descriptive commit message, spanning multiple lines if detailed explanation is needed.
5. Push to your fork of the repository and then send a pull-request through Github.

   +BEGIN_SRC shell

   git push mine some-topic-branch

   +END_SRC

6. A Basho engineer or community maintainer will review your patch and merge it into the main repository or send you feedback.