High-speed pseudorandom function (reference code)
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Reference implementation of SipHash, a family of pseudorandom functions optimized for speed on short messages.

SipHash was designed as a mitigation to hash-flooding DoS attacks. It is now used in the hash tables implementation of Python, Ruby, Perl 5, etc.

SipHash was designed by Jean-Philippe Aumasson and Daniel J. Bernstein.




will build tests for

  • SipHash-2-4, the default version of SipHash returning 64-bit tags
  • SipHash-2-4 with doubled tag size, i.e. 128-bit tags
  • HalfSipHash-2-4, a version of SipHash working with 32-bit words and returning 32-bit tags by default
  • HalfSipHash-2-4 with doubled tag size, i.e. 64-bit tags

verifies 64 test vectors, and


does the same and prints intermediate values.

The code can be adapted to implement SipHash-c-d, the version of SipHash with c compression rounds and d finalization rounds, by tweaking the lines

#define cROUNDS 2
#define dROUNDS 4

Obviously, if the number of rounds is modified then the test vectors won't verify.

Intellectual property

The SipHash reference code is released under CC0 license, a public domain-like licence.

We aren't aware of any patents or patent applications relevant to SipHash, and we aren't planning to apply for any.


The SipHash page includes

  • a list of third-party implementations and modules
  • a list of projects using SipHash
  • references to cryptanalysis results