csiphash 0.0.5
A CFFI-based implementation of SipHash24
License: UNLICENSE

csiphash.py
===========

`SipHash <https://131002.net/siphash/>`__ is a hash function and message
authentication code that is secure, fast and simple. It accepts a
128-bit secret key and a variable-length message, and returns a 64-bit
hash. It performs better than most cryptographic hash function-based
MACs (especially for short inputs), and offers much better security than
non-cryptographic hash functions, providing resistance against
hash-flooding DoS attacks. As a result, it is now used as the hash
function of choice for hash tables in Python, Ruby, Rust and Redis.

This Python package is the SipHash-2-4 `C reference
implementation <https://github.com/veorq/SipHash>`__, wrapped with
`CFFI <http://cffi.readthedocs.io>`__. It's incredibly fast: amortized
hashing times tested as follows on a mid-2015 MacBook Pro:

+----------------+-------------------------------------+
| Message Size   | Time per Hash (Amortized over 1M)   |
+================+=====================================+
| 43 bytes       | 4.89 microseconds                   |
+----------------+-------------------------------------+
| 256 bytes      | 5.00 microseconds                   |
+----------------+-------------------------------------+
| 1500 bytes     | 6.12 microseconds                   |
+----------------+-------------------------------------+
| 1 MiB          | 0.88 milliseconds                   |
+----------------+-------------------------------------+

Installation
------------

You can get this library with pip:

::

    pip install csiphash

Usage
-----

Currently there's just a single function, ``siphash24()``, that accepts
a secret key bytestring of length 16 and an arbitrary length bytestring
for the message, and returns an 8-byte digest bytestring:

.. code:: pycon

    >>> from csiphash import siphash24
    >>> siphash24(b'\x00' * 16, b'hello, world!\n')
    b'\xf1G4\x95\xa5\xaa\xc2b'

If you want to specify keys in hexadecimal, use ``.decode('hex')``:

.. code:: pycon

    >>> siphash24('abcdef01234567899876543210fedcba'.decode('hex'), b'hello, world!\n')
    '\xd3\xd4N\x1dk\x1f$='

If you want digests in hexadecimal, use ``.encode('hex')``:

.. code:: pycon

    >>> siphash24(b'\x00' * 16, b'hello, world!\n').encode('hex')
    'f1473495a5aac262'

License
-------

The reference C implementation of SipHash is bundled with this library.
It was written by Jean-Philippe Aumasson and Daniel J. Bernstein, and is
released under the
`CC0 <https://creativecommons.org/publicdomain/zero/1.0/>`__.

`Six <https://pythonhosted.org/six/>`__ is bundled with this library. It
was written by Benjamin Peterson, and is licensed under the `MIT
License <https://bitbucket.org/gutworth/six/raw/ca4580a5a648fc75abc568907e81abc80b05d58c/LICENSE>`__.

All other software in this library is released under the
`UNLICENSE <https://unlicense.org/>`__:

    This is free and unencumbered software released into the public
    domain.

    Anyone is free to copy, modify, publish, use, compile, sell, or
    distribute this software, either in source code form or as a
    compiled binary, for any purpose, commercial or non-commercial, and
    by any means.

    In jurisdictions that recognize copyright laws, the author or
    authors of this software dedicate any and all copyright interest in
    the software to the public domain. We make this dedication for the
    benefit of the public at large and to the detriment of our heirs and
    successors. We intend this dedication to be an overt act of
    relinquishment in perpetuity of all present and future rights to
    this software under copyright law.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
    EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
    NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
    CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
    TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
    SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

    For more information, please refer to http://unlicense.org/