SipHash: a fast short-input PRF

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): We propose that hash tables switch to SipHash as a hash function. Users of SipHash already include FreeBSD, OpenDNS, Perl 5, Ruby, or Rust.

The original SipHash returns 64-bit strings. An experimental version returning 128-bit strings was later created, based on demand from users.

Intellectual property: We aren't aware of any patents or patent applications relevant to SipHash, and we aren't planning to apply for any. The reference code of SipHash is released under CC0 license, a public domain-like license.

SipHash was designed by Contact:



Jointly with Martin Boßlet, we demonstrated weaknesses in MurmurHash (used in Ruby, Java, etc.), CityHash (used in Google), and in Python's hash. Some of the technologies affected have switched to SipHash. See this oCERT advisory, and the following resources:


Users of SipHash include:


Third-party implementations