siphash

pysiphash

A Python implementation of SipHash, a fast short-input PRF.

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.

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.