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README.md

SipHash in C

A pure C 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.

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

installation

Copy csiphash.c to your code directory and add the declaration somewhere:

uint64_t siphash24(const void *src,
                   unsigned long src_sz,
                   const char k[16]);

usage

Shortest program:

#include <stdio.h>
#include <stdint.h>
#include <string.h>

uint64_t siphash24(const void *src,
                   unsigned long src_sz,
                   const char key[16]);

int main() {
    char key[16] = {0,1,2,3,4,5,6,7,8,9,0xa,0xb,0xc,0xd,0xe,0xf};
    char *pt = "hello world!";
    uint64_t hash = siphash24(pt, strlen(pt), key);
    printf("plaintext=%s hash=%llu\n", pt, hash);
    return 0;
}

testing

Type make:

$ make
64 tests passed in 0.008ms, 125ns per test

license

This code is released under the MIT License, the full text of which can be found is in the header of csiphash.c.