pysiphash

A Python implementation of SipHash-2-4, a fast short-input PRF with a 128-bit key and 64-bit output.

Extract from the description:

SipHash is a family of pseudorandom functions (a.k.a. keyed hash
functions) optimized for speed on short messages.

Target applications include network traffic authentication and defense
against hash-flooding DoS attacks.

SipHash is secure, fast, and simple (for real):
* SipHash is simpler and faster than previous cryptographic algorithms
  (e.g. MACs based on universal hashing)
* SipHash is competitive in performance with insecure
  non-cryptographic algorithms (e.g. MurmurHash)
* We propose that hash tables switch to SipHash as a hash
  function. Users of SipHash already include OpenDNS, Perl 5, Ruby, or
  Rust.

Pysiphash is tested on Python 2.7 and Python 3.2.

Introductory blog post: https://idea.popcount.org/2013-01-24-siphash/

installation

Released pysiphash versions are available on pypi. To install it use easy_install or pip:

$ pip install siphash

or

$ easy_install siphash

usage

Pysiphash tries to follow the hashlib API. You can add data to the hash by calling an update method, or feed data directly to the constructor:

>>> import siphash
>>> key = '0123456789ABCDEF'
>>> sip = siphash.SipHash_2_4(key)
>>> sip.update('a')
>>> sip.hash()
12398370950267227270L

>>> siphash.SipHash_2_4(key, 'a').hash()
12398370950267227270L

To extract the hash as a numeric value call hash():

>>> siphash.SipHash_2_4(key, 'a').hash()
12398370950267227270L

Or digest() to get a raw 8-bytes string:

>>> siphash.SipHash_2_4(key, 'a').digest()
'\x86L3\x9c\xb0\xdc\x0f\xac'

Or hexdigest() for a 16-bytes hex encoding:

>>> siphash.SipHash_2_4(key, 'a').hexdigest()
'864c339cb0dc0fac'

testing

A series of sanity checks are present inline the main pysiphash code, to run it type:

$ python siphash/__init__.py
all tests ok

speed

Currently pysiphash is a pure-python code, so don't expect blazing speed. On my machine computing a hash from a ten byte string takes around 0.31 ms, and hashing 1MiB blob takes 770 ms.