- /* Copyright (c) 2016, Google Inc.
- *
- * Permission to use, copy, modify, and/or distribute this software for any
- * purpose with or without fee is hereby granted, provided that the above
- * copyright notice and this permission notice appear in all copies.
- *
- * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
- * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
- * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
- * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
- * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
- * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
- * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
-
- #include <assert.h>
- #include <string.h>
-
- #include <openssl/aes.h>
- #include <openssl/rand.h>
-
- #include "internal.h"
-
-
- extern uint16_t newhope_omegas_montgomery[];
- extern uint16_t newhope_omegas_inv_montgomery[];
-
- extern uint16_t newhope_psis_bitrev_montgomery[];
- extern uint16_t newhope_psis_inv_montgomery[];
-
- void NEWHOPE_POLY_frombytes(NEWHOPE_POLY* r, const uint8_t* a) {
- for (int i = 0; i < PARAM_N / 4; i++) {
- r->coeffs[4 * i + 0] =
- a[7 * i + 0] | (((uint16_t)a[7 * i + 1] & 0x3f) << 8);
- r->coeffs[4 * i + 1] = (a[7 * i + 1] >> 6) |
- (((uint16_t)a[7 * i + 2]) << 2) |
- (((uint16_t)a[7 * i + 3] & 0x0f) << 10);
- r->coeffs[4 * i + 2] = (a[7 * i + 3] >> 4) |
- (((uint16_t)a[7 * i + 4]) << 4) |
- (((uint16_t)a[7 * i + 5] & 0x03) << 12);
- r->coeffs[4 * i + 3] =
- (a[7 * i + 5] >> 2) | (((uint16_t)a[7 * i + 6]) << 6);
- }
- }
-
- void NEWHOPE_POLY_tobytes(uint8_t* r, const NEWHOPE_POLY* p) {
- uint16_t t0, t1, t2, t3, m;
- int16_t c;
- for (int i = 0; i < PARAM_N / 4; i++) {
- t0 = newhope_barrett_reduce(
- p->coeffs[4 * i + 0]); /* Make sure that coefficients
- have only 14 bits */
- t1 = newhope_barrett_reduce(p->coeffs[4 * i + 1]);
- t2 = newhope_barrett_reduce(p->coeffs[4 * i + 2]);
- t3 = newhope_barrett_reduce(p->coeffs[4 * i + 3]);
-
- m = t0 - PARAM_Q;
- c = m;
- c >>= 15;
- t0 = m ^ ((t0 ^ m) & c); /* Make sure that coefficients are in [0,q] */
-
- m = t1 - PARAM_Q;
- c = m;
- c >>= 15;
- t1 = m ^ ((t1 ^ m) & c); /* <Make sure that coefficients are in [0,q] */
-
- m = t2 - PARAM_Q;
- c = m;
- c >>= 15;
- t2 = m ^ ((t2 ^ m) & c); /* <Make sure that coefficients are in [0,q] */
-
- m = t3 - PARAM_Q;
- c = m;
- c >>= 15;
- t3 = m ^ ((t3 ^ m) & c); /* Make sure that coefficients are in [0,q] */
-
- r[7 * i + 0] = t0 & 0xff;
- r[7 * i + 1] = (t0 >> 8) | (t1 << 6);
- r[7 * i + 2] = (t1 >> 2);
- r[7 * i + 3] = (t1 >> 10) | (t2 << 4);
- r[7 * i + 4] = (t2 >> 4);
- r[7 * i + 5] = (t2 >> 12) | (t3 << 2);
- r[7 * i + 6] = (t3 >> 6);
- }
- }
-
- void newhope_poly_uniform(NEWHOPE_POLY* a, const uint8_t* seed) {
- /* The reference implementation uses SHAKE-128 here; this implementation uses
- * AES-CTR. Use half the seed for the initialization vector and half for the
- * key. */
- #if SEED_LENGTH != 2 * AES_BLOCK_SIZE
- #error "2 * seed length != AES_BLOCK_SIZE"
- #endif
- uint8_t ivec[AES_BLOCK_SIZE];
- memcpy(ivec, &seed[SEED_LENGTH / 2], SEED_LENGTH / 2);
- AES_KEY key;
- AES_set_encrypt_key(seed, 8 * SEED_LENGTH / 2, &key);
-
- /* AES state. */
- uint8_t ecount[AES_BLOCK_SIZE];
- memset(ecount, 0, AES_BLOCK_SIZE);
-
- /* Encrypt a block of zeros just to get the random bytes. With luck, 2688
- * bytes is enough. */
- uint8_t buf[AES_BLOCK_SIZE * 168];
- memset(buf, 0, sizeof(buf));
-
- unsigned int block_num = 0;
- AES_ctr128_encrypt(buf, buf, sizeof(buf), &key, ivec, ecount, &block_num);
-
- size_t pos = 0, coeff_num = 0;
- while (coeff_num < PARAM_N) {
- /* Specialized for q = 12889 */
- uint16_t val = (buf[pos] | ((uint16_t)buf[pos + 1] << 8)) & 0x3fff;
- if (val < PARAM_Q) {
- a->coeffs[coeff_num++] = val;
- }
-
- pos += 2;
- if (pos > sizeof(buf) - 2) {
- memset(buf, 0, sizeof(buf));
- AES_ctr128_encrypt(buf, buf, sizeof(buf), &key, ivec, ecount, &block_num);
- pos = 0;
- }
- }
- }
-
- void NEWHOPE_POLY_noise(NEWHOPE_POLY* r) {
- #if PARAM_K != 16
- #error "poly_getnoise in poly.c only supports k=16"
- #endif
-
- uint32_t tp[PARAM_N];
-
- /* The reference implementation calls ChaCha20 here. */
- RAND_bytes((uint8_t *) tp, sizeof(tp));
-
- for (size_t i = 0; i < PARAM_N; i++) {
- const uint32_t t = tp[i];
-
- uint32_t d = 0;
- for (size_t j = 0; j < 8; j++) {
- d += (t >> j) & 0x01010101;
- }
-
- const uint32_t a = ((d >> 8) & 0xff) + (d & 0xff);
- const uint32_t b = (d >> 24) + ((d >> 16) & 0xff);
- r->coeffs[i] = a + PARAM_Q - b;
- }
- }
-
- void newhope_poly_pointwise(NEWHOPE_POLY* r, const NEWHOPE_POLY* a,
- const NEWHOPE_POLY* b) {
- for (size_t i = 0; i < PARAM_N; i++) {
- uint16_t t = newhope_montgomery_reduce(3186 * b->coeffs[i]);
- /* t is now in Montgomery domain */
- r->coeffs[i] = newhope_montgomery_reduce(a->coeffs[i] * t);
- /* r->coeffs[i] is back in normal domain */
- }
- }
-
- void newhope_poly_add(NEWHOPE_POLY* r, const NEWHOPE_POLY* a,
- const NEWHOPE_POLY* b) {
- for (size_t i = 0; i < PARAM_N; i++) {
- r->coeffs[i] = newhope_barrett_reduce(a->coeffs[i] + b->coeffs[i]);
- }
- }
-
- void NEWHOPE_POLY_noise_ntt(NEWHOPE_POLY* r) {
- NEWHOPE_POLY_noise(r);
- /* Forward NTT transformation. Because we're operating on a noise polynomial,
- * we can regard the bits as already reversed and skip the bit-reversal
- * step:
- *
- * newhope_bitrev_vector(r->coeffs); */
- newhope_mul_coefficients(r->coeffs, newhope_psis_bitrev_montgomery);
- newhope_ntt((uint16_t *) r->coeffs, newhope_omegas_montgomery);
- }
-
- void newhope_poly_invntt(NEWHOPE_POLY* r) {
- newhope_bitrev_vector(r->coeffs);
- newhope_ntt((uint16_t *) r->coeffs, newhope_omegas_inv_montgomery);
- newhope_mul_coefficients(r->coeffs, newhope_psis_inv_montgomery);
- }
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