SipHash

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.

Usage

Running

  make

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, an experimental 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

  ./test

verifies 64 test vectors, and

  ./debug

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.

References

The SipHash page includes

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