C++ (Cpp) s_mp_mul_d_add_offset示例

示例#1

文件： mpmontg.c 项目： emaldona/nss

/*! c <- REDC( a * b ) mod N
    \param a < N  i.e. "reduced"
    \param b < N  i.e. "reduced"
    \param mmm modulus N and n0' of N
*/
mp_err
s_mp_mul_mont(const mp_int *a, const mp_int *b, mp_int *c,
              mp_mont_modulus *mmm)
{
    mp_digit *pb;
    mp_digit m_i;
    mp_err res;
    mp_size ib; /* "index b": index of current digit of B */
    mp_size useda, usedb;

    ARGCHK(a != NULL && b != NULL && c != NULL, MP_BADARG);

    if (MP_USED(a) < MP_USED(b)) {
        const mp_int *xch = b; /* switch a and b, to do fewer outer loops */
        b = a;
        a = xch;
    }

    MP_USED(c) = 1;
    MP_DIGIT(c, 0) = 0;
    ib = (MP_USED(&mmm->N) << 1) + 1;
    if ((res = s_mp_pad(c, ib)) != MP_OKAY)
        goto CLEANUP;

    useda = MP_USED(a);
    pb = MP_DIGITS(b);
    s_mpv_mul_d(MP_DIGITS(a), useda, *pb++, MP_DIGITS(c));
    s_mp_setz(MP_DIGITS(c) + useda + 1, ib - (useda + 1));
    m_i = MP_DIGIT(c, 0) * mmm->n0prime;
    s_mp_mul_d_add_offset(&mmm->N, m_i, c, 0);

    /* Outer loop:  Digits of b */
    usedb = MP_USED(b);
    for (ib = 1; ib < usedb; ib++) {
        mp_digit b_i = *pb++;

        /* Inner product:  Digits of a */
        if (b_i)
            s_mpv_mul_d_add_prop(MP_DIGITS(a), useda, b_i, MP_DIGITS(c) + ib);
        m_i = MP_DIGIT(c, ib) * mmm->n0prime;
        s_mp_mul_d_add_offset(&mmm->N, m_i, c, ib);
    }
    if (usedb < MP_USED(&mmm->N)) {
        for (usedb = MP_USED(&mmm->N); ib < usedb; ++ib) {
            m_i = MP_DIGIT(c, ib) * mmm->n0prime;
            s_mp_mul_d_add_offset(&mmm->N, m_i, c, ib);
        }
    }
    s_mp_clamp(c);
    s_mp_rshd(c, MP_USED(&mmm->N)); /* c /= R */
    if (s_mp_cmp(c, &mmm->N) >= 0) {
        MP_CHECKOK(s_mp_sub(c, &mmm->N));
    }
    res = MP_OKAY;

CLEANUP:
    return res;
}

示例#2

文件： mpmontg.c 项目： AlfredArouna/illumos-gate

/* computes T = REDC(T), 2^b == R */
mp_err s_mp_redc(mp_int *T, mp_mont_modulus *mmm)
{
  mp_err res;
  mp_size i;

  i = MP_USED(T) + MP_USED(&mmm->N) + 2;
  MP_CHECKOK( s_mp_pad(T, i) );
  for (i = 0; i < MP_USED(&mmm->N); ++i ) {
    mp_digit m_i = MP_DIGIT(T, i) * mmm->n0prime;
    /* T += N * m_i * (MP_RADIX ** i); */
    MP_CHECKOK( s_mp_mul_d_add_offset(&mmm->N, m_i, T, i) );
  }
  s_mp_clamp(T);

  /* T /= R */
  s_mp_div_2d(T, mmm->b); 

  if ((res = s_mp_cmp(T, &mmm->N)) >= 0) {
    /* T = T - N */
    MP_CHECKOK( s_mp_sub(T, &mmm->N) );
#ifdef DEBUG
    if ((res = mp_cmp(T, &mmm->N)) >= 0) {
      res = MP_UNDEF;
      goto CLEANUP;
    }
#endif
  }
  res = MP_OKAY;
CLEANUP:
  return res;
}