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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

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


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

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


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;


Type make:

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