text: /* 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) {
    int i;
    for (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) {
    int i;
    uint16_t t0, t1, t2, t3, m;
    int16_t c;
    for (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));
  
    size_t i;
    for (i = 0; i < PARAM_N; i++) {
      const uint32_t t = tp[i];
  
      size_t j;
      uint32_t d = 0;
      for (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) {
    size_t i;
    for (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) {
    size_t i;
    for (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);
  }
  