コード例 #1
0
ファイル: ge25519.c プロジェクト: piyushpandey013/bailingwire
void ge25519_pack(unsigned char r[32], const ge25519_p3 *p)
{
  fe25519 tx, ty, zi;
  fe25519_invert(&zi, &p->z); 
  fe25519_mul(&tx, &p->x, &zi);
  fe25519_mul(&ty, &p->y, &zi);
  fe25519_pack(r, &ty);
  r[31] ^= fe25519_getparity(&tx) << 7;
}
コード例 #2
0
ファイル: ge25519.c プロジェクト: Alexey-T/SynFTP
/* return 0 on success, -1 otherwise */
int ge25519_unpackneg_vartime(ge25519_p3 *r, const unsigned char p[32])
{
    unsigned char par;

    fe25519 t, chk, num, den, den2, den4, den6;
    fe25519_setone(&r->z);
    par = p[31] >> 7;
    fe25519_unpack(&r->y, p);
    fe25519_square(&num, &r->y); /* x = y^2 */
    fe25519_mul(&den, &num, &ge25519_ecd); /* den = dy^2 */
    fe25519_sub(&num, &num, &r->z); /* x = y^2-1 */
    fe25519_add(&den, &r->z, &den); /* den = dy^2+1 */

    /* Computation of sqrt(num/den) */
    /* 1.: computation of num^((p-5)/8)*den^((7p-35)/8) = (num*den^7)^((p-5)/8) */
    fe25519_square(&den2, &den);
    fe25519_square(&den4, &den2);
    fe25519_mul(&den6, &den4, &den2);
    fe25519_mul(&t, &den6, &num);
    fe25519_mul(&t, &t, &den);

    fe25519_pow2523(&t, &t);
    /* 2. computation of r->x = t * num * den^3 */
    fe25519_mul(&t, &t, &num);
    fe25519_mul(&t, &t, &den);
    fe25519_mul(&t, &t, &den);
    fe25519_mul(&r->x, &t, &den);

    /* 3. Check whether sqrt computation gave correct result, multiply by sqrt(-1) if not: */
    fe25519_square(&chk, &r->x);
    fe25519_mul(&chk, &chk, &den);
    if (!fe25519_iseq_vartime(&chk, &num)) {
        fe25519_mul(&r->x, &r->x, &ge25519_sqrtm1);
    }

    /* 4. Now we have one of the two square roots, except if input was not a square */
    fe25519_square(&chk, &r->x);
    fe25519_mul(&chk, &chk, &den);
    if (!fe25519_iseq_vartime(&chk, &num)) {
        return -1;
    }

    /* 5. Choose the desired square root according to parity: */
    if(fe25519_getparity(&r->x) != (1-par)) {
        fe25519_neg(&r->x, &r->x);
    }

    fe25519_mul(&r->t, &r->x, &r->y);

    return 0;
}