src/sig/falcon/pqclean_falcon-padded-512_avx2/rng.c

/*
 * PRNG and interface to the system RNG.
 *
 * ==========================(LICENSE BEGIN)============================
 *
 * Copyright (c) 2017-2019  Falcon Project
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * ===========================(LICENSE END)=============================
 *
 * @author   Thomas Pornin <thomas.pornin@nccgroup.com>
 */

#include <assert.h>

#include "inner.h"

/* see inner.h */
void
PQCLEAN_FALCONPADDED512_AVX2_prng_init(prng *p, inner_shake256_context *src) {
    inner_shake256_extract(src, p->state.d, 56);
    PQCLEAN_FALCONPADDED512_AVX2_prng_refill(p);
}

/*
 * PRNG based on ChaCha20.
 *
 * State consists in key (32 bytes) then IV (16 bytes) and block counter
 * (8 bytes). Normally, we should not care about local endianness (this
 * is for a PRNG), but for the NIST competition we need reproducible KAT
 * vectors that work across architectures, so we enforce little-endian
 * interpretation where applicable. Moreover, output words are "spread
 * out" over the output buffer with the interleaving pattern that is
 * naturally obtained from the AVX2 implementation that runs eight
 * ChaCha20 instances in parallel.
 *
 * The block counter is XORed into the first 8 bytes of the IV.
 */
void
PQCLEAN_FALCONPADDED512_AVX2_prng_refill(prng *p) {

    static const uint32_t CW[] = {
        0x61707865, 0x3320646e, 0x79622d32, 0x6b206574
    };

    uint64_t cc;
    size_t u;
    int i;
    uint32_t *sw;
    union {
        uint32_t w[16];
        __m256i y[2];  /* for alignment */
    } t;
    __m256i state[16], init[16];

    sw = (uint32_t *)p->state.d;

    /*
     * XOR next counter values into state.
     */
    cc = *(uint64_t *)(p->state.d + 48);
    for (u = 0; u < 8; u ++) {
        t.w[u] = (uint32_t)(cc + u);
        t.w[u + 8] = (uint32_t)((cc + u) >> 32);
    }
    *(uint64_t *)(p->state.d + 48) = cc + 8;

    /*
     * Load state.
     */
    for (u = 0; u < 4; u ++) {
        state[u] = init[u] =
                       _mm256_broadcastd_epi32(_mm_cvtsi32_si128((int)CW[u]));
    }
    for (u = 0; u < 10; u ++) {
        state[u + 4] = init[u + 4] =
                           _mm256_broadcastd_epi32(_mm_cvtsi32_si128((int)sw[u]));
    }
    state[14] = init[14] = _mm256_xor_si256(
                               _mm256_broadcastd_epi32(_mm_cvtsi32_si128((int)sw[10])),
                               _mm256_loadu_si256((__m256i *)&t.w[0]));
    state[15] = init[15] = _mm256_xor_si256(
                               _mm256_broadcastd_epi32(_mm_cvtsi32_si128((int)sw[11])),
                               _mm256_loadu_si256((__m256i *)&t.w[8]));

    /*
     * Do all rounds.
     */
    for (i = 0; i < 10; i ++) {

#define QROUND(a, b, c, d)   do { \
        state[a] = _mm256_add_epi32(state[a], state[b]); \
        state[d] = _mm256_xor_si256(state[d], state[a]); \
        state[d] = _mm256_or_si256( \
                                    _mm256_slli_epi32(state[d], 16), \
                                    _mm256_srli_epi32(state[d], 16)); \
        state[c] = _mm256_add_epi32(state[c], state[d]); \
        state[b] = _mm256_xor_si256(state[b], state[c]); \
        state[b] = _mm256_or_si256( \
                                    _mm256_slli_epi32(state[b], 12), \
                                    _mm256_srli_epi32(state[b], 20)); \
        state[a] = _mm256_add_epi32(state[a], state[b]); \
        state[d] = _mm256_xor_si256(state[d], state[a]); \
        state[d] = _mm256_or_si256( \
                                    _mm256_slli_epi32(state[d],  8), \
                                    _mm256_srli_epi32(state[d], 24)); \
        state[c] = _mm256_add_epi32(state[c], state[d]); \
        state[b] = _mm256_xor_si256(state[b], state[c]); \
        state[b] = _mm256_or_si256( \
                                    _mm256_slli_epi32(state[b], 7), \
                                    _mm256_srli_epi32(state[b], 25)); \
    } while (0)

        QROUND( 0,  4,  8, 12);
        QROUND( 1,  5,  9, 13);
        QROUND( 2,  6, 10, 14);
        QROUND( 3,  7, 11, 15);
        QROUND( 0,  5, 10, 15);
        QROUND( 1,  6, 11, 12);
        QROUND( 2,  7,  8, 13);
        QROUND( 3,  4,  9, 14);

#undef QROUND

    }

    /*
     * Add initial state back and encode the result in the destination
     * buffer. We can dump the AVX2 values "as is" because the non-AVX2
     * code uses a compatible order of values.
     */
    for (u = 0; u < 16; u ++) {
        _mm256_storeu_si256((__m256i *)&p->buf.d[u << 5],
                            _mm256_add_epi32(state[u], init[u]));
    }

    p->ptr = 0;
}

/* see inner.h */
void
PQCLEAN_FALCONPADDED512_AVX2_prng_get_bytes(prng *p, void *dst, size_t len) {
    uint8_t *buf;

    buf = dst;
    while (len > 0) {
        size_t clen;

        clen = (sizeof p->buf.d) - p->ptr;
        if (clen > len) {
            clen = len;
        }
        memcpy(buf, p->buf.d, clen);
        buf += clen;
        len -= clen;
        p->ptr += clen;
        if (p->ptr == sizeof p->buf.d) {
            PQCLEAN_FALCONPADDED512_AVX2_prng_refill(p);
        }
    }
}