C11 SHA-3

September 5, 2023

This weekend I put together a C11 implementation of the following SHA-3 algorithms from FIPS 202, SP 800-185, and the draft KangarooTwelve and TurboSHAKE specification:

  • SHA3-224, SHA3-256, SHA3-384, and SHA3-512
  • SHAKE128 and SHAKE256
  • HMAC-SHA3-224, HMAC-SHA3-256, HMAC-SHA3-384, and HMAC-SHA3-512
  • cSHAKE128, cSHAKE128-XOF, cSHAKE256, and cSHAKE256-XOF
  • KMAC128, KMAC128-XOF, KMAC256, and KMAC256-XOF
  • TupleHash128, TupleHash128-XOF, TupleHash256, and TupleHash256-XOF
  • ParallelHash128, ParallelHash128-XOF, ParallelHash256, and ParallelHash256-XOF
  • TurboSHAKE128 and TurboSHAKE256
  • KangarooTwelve

Git Repository, API Documentation



// example.c: print hex-encode sha3-256 hash of each command-line argument
// build:
//   cc -o example -std=c11 -O3 -W -Wall -Wextra -Werror -pedantic -march=native -mtune=native example.c sha3.c
#include <stdint.h> // uint8_t
#include <stdio.h> // printf()
#include <string.h> // strlen()
#include "sha3.h" // sha3_256()

// print hex-encoded buffer to stdout.
static void print_hex(const uint8_t * const buf, const size_t len) {
  for (size_t i = 0; i < len; i++) {
    printf("%02x", buf[i]);

int main(int argc, char *argv[]) {
  // loop over command-line arguments
  for (int i = 1; i < argc; i++) {
    // hash argument
    uint8_t buf[32] = { 0 };
    sha3_256((uint8_t*) argv[i], strlen(argv[i]), buf);

    // print argument and hex-encoded hash
    printf("\"%s\",", argv[i]);
    print_hex(buf, sizeof(buf));
    fputs("\n", stdout);

  // return success
  return 0;



> ./example asdf foo bar


Update (2023-09-07): Released v0.2 with TurboSHAKE128, TurboSHAKE256, KangarooTwelve, and an examples/ directory.

Update (2023-09-18): Released v0.3 with AVX-512 support (~3x faster) and miscellaneous small fixes.

Update (2023-10-15): Released v0.4 with lots of documentation improvements.

Update (2023-10-19): Released v0.5 with more documentation improvements and additional examples. added online API documentation.

Update (2024-03-02): Released v0.6 with speed improvements, simplified SHAKE API, and documentation updates. Added CAVP test vectors.