sha3_api.c

//  sha3_api.c
//  Markku-Juhani O. Saarinen <mjos@iki.fi>.  See LICENSE.

//  === FIPS 202: SHA-3 hash and SHAKE eXtensible Output Functions (XOF)
//      Hash padding mode code for testing permutation implementations.

#ifndef SLOTH_NO_SHA3
#include "sha3_api.h"

//  These functions have not been optimized for performance -- they are
//  here just to facilitate testing of the permutation code implementations.

//  initialize the context for SHA3

void sha3_init(sha3_ctx_t *c, int mdlen)
{
    int i;

    for (i = 0; i < 25; i++)
        c->st.d[i] = 0;
    c->mdlen = mdlen;           //  in SHAKE; if 0, padding done
    c->rsiz = 200 - 2 * mdlen;
    c->pt = 0;
}

//  update state with more data

void sha3_update(sha3_ctx_t *c, const void *data, size_t len)
{
    size_t i;
    int j;

    j = c->pt;
    for (i = 0; i < len; i++) {
        c->st.b[j++] ^= ((const uint8_t *) data)[i];
        if (j >= c->rsiz) {
            keccak_f1600(c->st.d);
            j = 0;
        }
    }
    c->pt = j;
}

//  finalize and output a hash

void sha3_final(sha3_ctx_t *c, uint8_t *md)
{
    int i;

    c->st.b[c->pt] ^= 0x06;
    c->st.b[c->rsiz - 1] ^= 0x80;
    keccak_f1600(c->st.d);

    for (i = 0; i < c->mdlen; i++) {
        md[i] = c->st.b[i];
    }
}

//  compute a SHA-3 hash "md" of "mdlen" bytes from data in "in"

void *sha3(uint8_t *md, int mdlen, const void *in, size_t inlen)
{
    sha3_ctx_t sha3;

    sha3_init(&sha3, mdlen);
    sha3_update(&sha3, in, inlen);
    sha3_final(&sha3, md);

    return md;
}

//  SHAKE128 and SHAKE256 extensible-output functionality
//  squeeze output

void shake_out(sha3_ctx_t *c, uint8_t *out, size_t len)
{
    size_t  i;
    int j;

    //  add padding on the first call
    if (c->mdlen != 0) {
        c->st.b[c->pt] ^= 0x1F;
        c->st.b[c->rsiz - 1] ^= 0x80;
        keccak_f1600(c->st.d);
        c->pt = 0;
        c->mdlen = 0;
    }

    j = c->pt;
    for (i = 0; i < len; i++) {
        if (j >= c->rsiz) {
            keccak_f1600(c->st.d);
            j = 0;
        }
        out[i] = c->st.b[j++];
    }
    c->pt = j;
}

//  SLOTH_NO_SHA3
#endif