sha3.c

//  sha3.c
//  2018-06-29  Markku-Juhani O. Saarinen <markku@teserakt.io>

//  (c) 2018 Copyright Teserakt AG

//  From tiny_sha3 (dated 2011-11-19)

#include "sha3.h"
#include "string.h"

// Initialize the context for SHA3

int sha3_init(sha3_ctx_t *c, int mdlen)
{
    memset(c->b, 0, 200);
    c->mdlen = mdlen;
    c->rsiz = 200 - 2 * mdlen;
    c->pt = 0;

    return 0;
}

// update state with more data

int 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->b[j++] ^= ((const uint8_t *) data)[i];
        if (j >= c->rsiz) {
            keccak_f1600(c->b, KECCAKF_ROUNDS);
            j = 0;
        }
    }
    c->pt = j;

    return 0;
}

// finalize and output a hash

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

    c->b[c->pt] ^= 0x06;
    c->b[c->rsiz - 1] ^= 0x80;
    keccak_f1600(c->b, KECCAKF_ROUNDS);

    for (i = 0; i < c->mdlen; i++) {
        ((uint8_t *) md)[i] = c->b[i];
    }

    return 0;
}


// compute a SHA-3 hash (md) of given byte length from "in"

void *sha3(const void *in, size_t inlen, void *md, int mdlen)
{
    sha3_init(&common_sha3_ctx, mdlen);
    sha3_update(&common_sha3_ctx, in, inlen);
    sha3_final(md, &common_sha3_ctx);

    return md;
}

// SHAKE128 and SHAKE256 extensible-output functionality

void shake_xof(sha3_ctx_t *c)
{
    c->b[c->pt] ^= 0x1F;
    c->b[c->rsiz - 1] ^= 0x80;
    keccak_f1600(c->b, KECCAKF_ROUNDS);
    c->pt = 0;
}

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

    j = c->pt;
    for (i = 0; i < len; i++) {
        if (j >= c->rsiz) {
            keccak_f1600(c->b, KECCAKF_ROUNDS);
            j = 0;
        }
        ((uint8_t *) out)[i] = c->b[j++];
    }
    c->pt = j;
}