/**
Double an ECC point
@param P The point to double
@param R [out] The destination of the double
@param modulus The modulus of the field the ECC curve is in
@param mp The "b" value from montgomery_setup()
@return CRYPT_OK on success
*/
int ltc_ecc_projective_dbl_point(ecc_point *P, ecc_point *R, void *modulus, void *mp)
{
void *t1, *t2;
int err;
LTC_ARGCHK(P != NULL);
LTC_ARGCHK(R != NULL);
LTC_ARGCHK(modulus != NULL);
LTC_ARGCHK(mp != NULL);
if ((err = mp_init_multi(&t1, &t2, NULL)) != CRYPT_OK) {
return err;
}
if (P != R) {
if ((err = mp_copy(P->x, R->x)) != CRYPT_OK) { goto done; }
if ((err = mp_copy(P->y, R->y)) != CRYPT_OK) { goto done; }
if ((err = mp_copy(P->z, R->z)) != CRYPT_OK) { goto done; }
}
/* t1 = Z * Z */
if ((err = mp_sqr(R->z, t1)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(t1, modulus, mp)) != CRYPT_OK) { goto done; }
/* Z = Y * Z */
if ((err = mp_mul(R->z, R->y, R->z)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(R->z, modulus, mp)) != CRYPT_OK) { goto done; }
/* Z = 2Z */
if ((err = mp_add(R->z, R->z, R->z)) != CRYPT_OK) { goto done; }
if (mp_cmp(R->z, modulus) != LTC_MP_LT) {
if ((err = mp_sub(R->z, modulus, R->z)) != CRYPT_OK) { goto done; }
}
/* T2 = X - T1 */
if ((err = mp_sub(R->x, t1, t2)) != CRYPT_OK) { goto done; }
if (mp_cmp_d(t2, 0) == LTC_MP_LT) {
if ((err = mp_add(t2, modulus, t2)) != CRYPT_OK) { goto done; }
}
/* T1 = X + T1 */
if ((err = mp_add(t1, R->x, t1)) != CRYPT_OK) { goto done; }
if (mp_cmp(t1, modulus) != LTC_MP_LT) {
if ((err = mp_sub(t1, modulus, t1)) != CRYPT_OK) { goto done; }
}
/* T2 = T1 * T2 */
if ((err = mp_mul(t1, t2, t2)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(t2, modulus, mp)) != CRYPT_OK) { goto done; }
/* T1 = 2T2 */
if ((err = mp_add(t2, t2, t1)) != CRYPT_OK) { goto done; }
if (mp_cmp(t1, modulus) != LTC_MP_LT) {
if ((err = mp_sub(t1, modulus, t1)) != CRYPT_OK) { goto done; }
}
/* T1 = T1 + T2 */
if ((err = mp_add(t1, t2, t1)) != CRYPT_OK) { goto done; }
if (mp_cmp(t1, modulus) != LTC_MP_LT) {
if ((err = mp_sub(t1, modulus, t1)) != CRYPT_OK) { goto done; }
}
/* Y = 2Y */
if ((err = mp_add(R->y, R->y, R->y)) != CRYPT_OK) { goto done; }
if (mp_cmp(R->y, modulus) != LTC_MP_LT) {
if ((err = mp_sub(R->y, modulus, R->y)) != CRYPT_OK) { goto done; }
}
/* Y = Y * Y */
if ((err = mp_sqr(R->y, R->y)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(R->y, modulus, mp)) != CRYPT_OK) { goto done; }
/* T2 = Y * Y */
if ((err = mp_sqr(R->y, t2)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(t2, modulus, mp)) != CRYPT_OK) { goto done; }
/* T2 = T2/2 */
if (mp_isodd(t2)) {
if ((err = mp_add(t2, modulus, t2)) != CRYPT_OK) { goto done; }
}
if ((err = mp_div_2(t2, t2)) != CRYPT_OK) { goto done; }
/* Y = Y * X */
if ((err = mp_mul(R->y, R->x, R->y)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(R->y, modulus, mp)) != CRYPT_OK) { goto done; }
/* X = T1 * T1 */
if ((err = mp_sqr(t1, R->x)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(R->x, modulus, mp)) != CRYPT_OK) { goto done; }
/* X = X - Y */
if ((err = mp_sub(R->x, R->y, R->x)) != CRYPT_OK) { goto done; }
if (mp_cmp_d(R->x, 0) == LTC_MP_LT) {
if ((err = mp_add(R->x, modulus, R->x)) != CRYPT_OK) { goto done; }
}
/* X = X - Y */
if ((err = mp_sub(R->x, R->y, R->x)) != CRYPT_OK) { goto done; }
if (mp_cmp_d(R->x, 0) == LTC_MP_LT) {
if ((err = mp_add(R->x, modulus, R->x)) != CRYPT_OK) { goto done; }
}
/* Y = Y - X */
if ((err = mp_sub(R->y, R->x, R->y)) != CRYPT_OK) { goto done; }
if (mp_cmp_d(R->y, 0) == LTC_MP_LT) {
if ((err = mp_add(R->y, modulus, R->y)) != CRYPT_OK) { goto done; }
}
/* Y = Y * T1 */
if ((err = mp_mul(R->y, t1, R->y)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(R->y, modulus, mp)) != CRYPT_OK) { goto done; }
/* Y = Y - T2 */
if ((err = mp_sub(R->y, t2, R->y)) != CRYPT_OK) { goto done; }
if (mp_cmp_d(R->y, 0) == LTC_MP_LT) {
if ((err = mp_add(R->y, modulus, R->y)) != CRYPT_OK) { goto done; }
}
err = CRYPT_OK;
done:
mp_clear_multi(t1, t2, NULL);
return err;
}
/* this is a shell function that calls either the normal or Montgomery
* exptmod functions. Originally the call to the montgomery code was
* embedded in the normal function but that wasted alot of stack space
* for nothing (since 99% of the time the Montgomery code would be called)
*/
int mp_exptmod(const mp_int *G, const mp_int *X, const mp_int *P, mp_int *Y)
{
int dr;
/* modulus P must be positive */
if (P->sign == MP_NEG) {
return MP_VAL;
}
/* if exponent X is negative we have to recurse */
if (X->sign == MP_NEG) {
#ifdef BN_MP_INVMOD_C
mp_int tmpG, tmpX;
int err;
/* first compute 1/G mod P */
if ((err = mp_init(&tmpG)) != MP_OKAY) {
return err;
}
if ((err = mp_invmod(G, P, &tmpG)) != MP_OKAY) {
mp_clear(&tmpG);
return err;
}
/* now get |X| */
if ((err = mp_init(&tmpX)) != MP_OKAY) {
mp_clear(&tmpG);
return err;
}
if ((err = mp_abs(X, &tmpX)) != MP_OKAY) {
mp_clear_multi(&tmpG, &tmpX, NULL);
return err;
}
/* and now compute (1/G)**|X| instead of G**X [X < 0] */
err = mp_exptmod(&tmpG, &tmpX, P, Y);
mp_clear_multi(&tmpG, &tmpX, NULL);
return err;
#else
/* no invmod */
return MP_VAL;
#endif
}
/* modified diminished radix reduction */
#if defined(BN_MP_REDUCE_IS_2K_L_C) && defined(BN_MP_REDUCE_2K_L_C) && defined(BN_S_MP_EXPTMOD_C)
if (mp_reduce_is_2k_l(P) == MP_YES) {
return s_mp_exptmod(G, X, P, Y, 1);
}
#endif
#ifdef BN_MP_DR_IS_MODULUS_C
/* is it a DR modulus? */
dr = mp_dr_is_modulus(P);
#else
/* default to no */
dr = 0;
#endif
#ifdef BN_MP_REDUCE_IS_2K_C
/* if not, is it a unrestricted DR modulus? */
if (dr == 0) {
dr = mp_reduce_is_2k(P) << 1;
}
#endif
/* if the modulus is odd or dr != 0 use the montgomery method */
#ifdef BN_MP_EXPTMOD_FAST_C
if ((mp_isodd(P) == MP_YES) || (dr != 0)) {
return mp_exptmod_fast(G, X, P, Y, dr);
} else {
#endif
#ifdef BN_S_MP_EXPTMOD_C
/* otherwise use the generic Barrett reduction technique */
return s_mp_exptmod(G, X, P, Y, 0);
#else
/* no exptmod for evens */
return MP_VAL;
#endif
#ifdef BN_MP_EXPTMOD_FAST_C
}
#endif
}
/* hac 14.61, pp608 */
int mp_invmod_slow (mp_int * a, mp_int * b, mp_int * c)
{
mp_int x, y, u, v, A, B, C, D;
int res;
/* b cannot be negative */
if (b->sign == MP_NEG || mp_iszero(b) == 1) {
return MP_VAL;
}
/* init temps */
if ((res = mp_init_multi(&x, &y, &u, &v,
&A, &B, &C, &D, NULL)) != MP_OKAY) {
return res;
}
/* x = a, y = b */
if ((res = mp_mod(a, b, &x)) != MP_OKAY) {
goto LBL_ERR;
}
if ((res = mp_copy (b, &y)) != MP_OKAY) {
goto LBL_ERR;
}
/* 2. [modified] if x,y are both even then return an error! */
if (mp_iseven (&x) == 1 && mp_iseven (&y) == 1) {
res = MP_VAL;
goto LBL_ERR;
}
/* 3. u=x, v=y, A=1, B=0, C=0,D=1 */
if ((res = mp_copy (&x, &u)) != MP_OKAY) {
goto LBL_ERR;
}
if ((res = mp_copy (&y, &v)) != MP_OKAY) {
goto LBL_ERR;
}
mp_set (&A, 1);
mp_set (&D, 1);
top:
/* 4. while u is even do */
while (mp_iseven (&u) == 1) {
/* 4.1 u = u/2 */
if ((res = mp_div_2 (&u, &u)) != MP_OKAY) {
goto LBL_ERR;
}
/* 4.2 if A or B is odd then */
if (mp_isodd (&A) == 1 || mp_isodd (&B) == 1) {
/* A = (A+y)/2, B = (B-x)/2 */
if ((res = mp_add (&A, &y, &A)) != MP_OKAY) {
goto LBL_ERR;
}
if ((res = mp_sub (&B, &x, &B)) != MP_OKAY) {
goto LBL_ERR;
}
}
/* A = A/2, B = B/2 */
if ((res = mp_div_2 (&A, &A)) != MP_OKAY) {
goto LBL_ERR;
}
if ((res = mp_div_2 (&B, &B)) != MP_OKAY) {
goto LBL_ERR;
}
}
/* 5. while v is even do */
while (mp_iseven (&v) == 1) {
/* 5.1 v = v/2 */
if ((res = mp_div_2 (&v, &v)) != MP_OKAY) {
goto LBL_ERR;
}
/* 5.2 if C or D is odd then */
if (mp_isodd (&C) == 1 || mp_isodd (&D) == 1) {
/* C = (C+y)/2, D = (D-x)/2 */
if ((res = mp_add (&C, &y, &C)) != MP_OKAY) {
goto LBL_ERR;
}
if ((res = mp_sub (&D, &x, &D)) != MP_OKAY) {
goto LBL_ERR;
}
}
/* C = C/2, D = D/2 */
if ((res = mp_div_2 (&C, &C)) != MP_OKAY) {
goto LBL_ERR;
}
if ((res = mp_div_2 (&D, &D)) != MP_OKAY) {
goto LBL_ERR;
}
}
/* 6. if u >= v then */
if (mp_cmp (&u, &v) != MP_LT) {
/* u = u - v, A = A - C, B = B - D */
if ((res = mp_sub (&u, &v, &u)) != MP_OKAY) {
goto LBL_ERR;
}
if ((res = mp_sub (&A, &C, &A)) != MP_OKAY) {
goto LBL_ERR;
}
if ((res = mp_sub (&B, &D, &B)) != MP_OKAY) {
goto LBL_ERR;
}
} else {
/* v - v - u, C = C - A, D = D - B */
if ((res = mp_sub (&v, &u, &v)) != MP_OKAY) {
goto LBL_ERR;
}
if ((res = mp_sub (&C, &A, &C)) != MP_OKAY) {
goto LBL_ERR;
}
if ((res = mp_sub (&D, &B, &D)) != MP_OKAY) {
goto LBL_ERR;
}
}
/* if not zero goto step 4 */
if (mp_iszero (&u) == 0)
goto top;
/* now a = C, b = D, gcd == g*v */
/* if v != 1 then there is no inverse */
if (mp_cmp_d (&v, 1) != MP_EQ) {
res = MP_VAL;
goto LBL_ERR;
}
/* if its too low */
while (mp_cmp_d(&C, 0) == MP_LT) {
if ((res = mp_add(&C, b, &C)) != MP_OKAY) {
goto LBL_ERR;
}
}
/* too big */
while (mp_cmp_mag(&C, b) != MP_LT) {
if ((res = mp_sub(&C, b, &C)) != MP_OKAY) {
goto LBL_ERR;
}
}
/* C is now the inverse */
mp_exch (&C, c);
res = MP_OKAY;
LBL_ERR:mp_clear_multi (&x, &y, &u, &v, &A, &B, &C, &D, NULL);
return res;
}
/**
Add two ECC points
@param P The point to add
@param Q The point to add
@param R [out] The destination of the double
@param modulus The modulus of the field the ECC curve is in
@param mp The "b" value from montgomery_setup()
@return CRYPT_OK on success
*/
int ltc_ecc_projective_add_point(ecc_point *P, ecc_point *Q, ecc_point *R, void *modulus, void *mp)
{
void *t1, *t2, *x, *y, *z;
int err;
LTC_ARGCHK(P != NULL);
LTC_ARGCHK(Q != NULL);
LTC_ARGCHK(R != NULL);
LTC_ARGCHK(modulus != NULL);
LTC_ARGCHK(mp != NULL);
if ((err = mp_init_multi(&t1, &t2, &x, &y, &z, NULL)) != CRYPT_OK) {
return err;
}
/* should we dbl instead? */
if ((err = mp_sub(modulus, Q->y, t1)) != CRYPT_OK) { goto done; }
if ( (mp_cmp(P->x, Q->x) == LTC_MP_EQ) &&
(Q->z != NULL && mp_cmp(P->z, Q->z) == LTC_MP_EQ) &&
(mp_cmp(P->y, Q->y) == LTC_MP_EQ || mp_cmp(P->y, t1) == LTC_MP_EQ)) {
mp_clear_multi(t1, t2, x, y, z, NULL);
return ltc_ecc_projective_dbl_point(P, R, modulus, mp);
}
if ((err = mp_copy(P->x, x)) != CRYPT_OK) { goto done; }
if ((err = mp_copy(P->y, y)) != CRYPT_OK) { goto done; }
if ((err = mp_copy(P->z, z)) != CRYPT_OK) { goto done; }
/* if Z is one then these are no-operations */
if (Q->z != NULL) {
/* T1 = Z' * Z' */
if ((err = mp_sqr(Q->z, t1)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(t1, modulus, mp)) != CRYPT_OK) { goto done; }
/* X = X * T1 */
if ((err = mp_mul(t1, x, x)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(x, modulus, mp)) != CRYPT_OK) { goto done; }
/* T1 = Z' * T1 */
if ((err = mp_mul(Q->z, t1, t1)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(t1, modulus, mp)) != CRYPT_OK) { goto done; }
/* Y = Y * T1 */
if ((err = mp_mul(t1, y, y)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(y, modulus, mp)) != CRYPT_OK) { goto done; }
}
/* T1 = Z*Z */
if ((err = mp_sqr(z, t1)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(t1, modulus, mp)) != CRYPT_OK) { goto done; }
/* T2 = X' * T1 */
if ((err = mp_mul(Q->x, t1, t2)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(t2, modulus, mp)) != CRYPT_OK) { goto done; }
/* T1 = Z * T1 */
if ((err = mp_mul(z, t1, t1)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(t1, modulus, mp)) != CRYPT_OK) { goto done; }
/* T1 = Y' * T1 */
if ((err = mp_mul(Q->y, t1, t1)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(t1, modulus, mp)) != CRYPT_OK) { goto done; }
/* Y = Y - T1 */
if ((err = mp_sub(y, t1, y)) != CRYPT_OK) { goto done; }
if (mp_cmp_d(y, 0) == LTC_MP_LT) {
if ((err = mp_add(y, modulus, y)) != CRYPT_OK) { goto done; }
}
/* T1 = 2T1 */
if ((err = mp_add(t1, t1, t1)) != CRYPT_OK) { goto done; }
if (mp_cmp(t1, modulus) != LTC_MP_LT) {
if ((err = mp_sub(t1, modulus, t1)) != CRYPT_OK) { goto done; }
}
/* T1 = Y + T1 */
if ((err = mp_add(t1, y, t1)) != CRYPT_OK) { goto done; }
if (mp_cmp(t1, modulus) != LTC_MP_LT) {
if ((err = mp_sub(t1, modulus, t1)) != CRYPT_OK) { goto done; }
}
/* X = X - T2 */
if ((err = mp_sub(x, t2, x)) != CRYPT_OK) { goto done; }
if (mp_cmp_d(x, 0) == LTC_MP_LT) {
if ((err = mp_add(x, modulus, x)) != CRYPT_OK) { goto done; }
}
/* T2 = 2T2 */
if ((err = mp_add(t2, t2, t2)) != CRYPT_OK) { goto done; }
if (mp_cmp(t2, modulus) != LTC_MP_LT) {
if ((err = mp_sub(t2, modulus, t2)) != CRYPT_OK) { goto done; }
}
/* T2 = X + T2 */
if ((err = mp_add(t2, x, t2)) != CRYPT_OK) { goto done; }
if (mp_cmp(t2, modulus) != LTC_MP_LT) {
if ((err = mp_sub(t2, modulus, t2)) != CRYPT_OK) { goto done; }
}
/* if Z' != 1 */
if (Q->z != NULL) {
/* Z = Z * Z' */
if ((err = mp_mul(z, Q->z, z)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(z, modulus, mp)) != CRYPT_OK) { goto done; }
}
/* Z = Z * X */
if ((err = mp_mul(z, x, z)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(z, modulus, mp)) != CRYPT_OK) { goto done; }
/* T1 = T1 * X */
if ((err = mp_mul(t1, x, t1)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(t1, modulus, mp)) != CRYPT_OK) { goto done; }
/* X = X * X */
if ((err = mp_sqr(x, x)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(x, modulus, mp)) != CRYPT_OK) { goto done; }
/* T2 = T2 * x */
if ((err = mp_mul(t2, x, t2)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(t2, modulus, mp)) != CRYPT_OK) { goto done; }
/* T1 = T1 * X */
if ((err = mp_mul(t1, x, t1)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(t1, modulus, mp)) != CRYPT_OK) { goto done; }
/* X = Y*Y */
if ((err = mp_sqr(y, x)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(x, modulus, mp)) != CRYPT_OK) { goto done; }
/* X = X - T2 */
if ((err = mp_sub(x, t2, x)) != CRYPT_OK) { goto done; }
if (mp_cmp_d(x, 0) == LTC_MP_LT) {
if ((err = mp_add(x, modulus, x)) != CRYPT_OK) { goto done; }
}
/* T2 = T2 - X */
if ((err = mp_sub(t2, x, t2)) != CRYPT_OK) { goto done; }
if (mp_cmp_d(t2, 0) == LTC_MP_LT) {
if ((err = mp_add(t2, modulus, t2)) != CRYPT_OK) { goto done; }
}
/* T2 = T2 - X */
if ((err = mp_sub(t2, x, t2)) != CRYPT_OK) { goto done; }
if (mp_cmp_d(t2, 0) == LTC_MP_LT) {
if ((err = mp_add(t2, modulus, t2)) != CRYPT_OK) { goto done; }
}
/* T2 = T2 * Y */
if ((err = mp_mul(t2, y, t2)) != CRYPT_OK) { goto done; }
if ((err = mp_montgomery_reduce(t2, modulus, mp)) != CRYPT_OK) { goto done; }
/* Y = T2 - T1 */
if ((err = mp_sub(t2, t1, y)) != CRYPT_OK) { goto done; }
if (mp_cmp_d(y, 0) == LTC_MP_LT) {
if ((err = mp_add(y, modulus, y)) != CRYPT_OK) { goto done; }
}
/* Y = Y/2 */
if (mp_isodd(y)) {
if ((err = mp_add(y, modulus, y)) != CRYPT_OK) { goto done; }
}
if ((err = mp_div_2(y, y)) != CRYPT_OK) { goto done; }
if ((err = mp_copy(x, R->x)) != CRYPT_OK) { goto done; }
if ((err = mp_copy(y, R->y)) != CRYPT_OK) { goto done; }
if ((err = mp_copy(z, R->z)) != CRYPT_OK) { goto done; }
err = CRYPT_OK;
done:
mp_clear_multi(t1, t2, x, y, z, NULL);
return err;
}
/* Computes R = 2P. Elliptic curve points P and R can be identical. Uses
* Jacobian coordinates.
*
* Assumes input is already field-encoded using field_enc, and returns
* output that is still field-encoded.
*
* This routine implements Point Doubling in the Jacobian Projective
* space as described in the paper "Efficient elliptic curve exponentiation
* using mixed coordinates", by H. Cohen, A Miyaji, T. Ono.
*/
mp_err
ec_GFp_pt_dbl_jac(const mp_int *px, const mp_int *py, const mp_int *pz,
mp_int *rx, mp_int *ry, mp_int *rz, const ECGroup *group)
{
mp_err res = MP_OKAY;
mp_int t0, t1, M, S;
MP_DIGITS(&t0) = 0;
MP_DIGITS(&t1) = 0;
MP_DIGITS(&M) = 0;
MP_DIGITS(&S) = 0;
MP_CHECKOK(mp_init(&t0));
MP_CHECKOK(mp_init(&t1));
MP_CHECKOK(mp_init(&M));
MP_CHECKOK(mp_init(&S));
/* P == inf or P == -P */
if (ec_GFp_pt_is_inf_jac(px, py, pz) == MP_YES || mp_cmp_z(py) == 0) {
MP_CHECKOK(ec_GFp_pt_set_inf_jac(rx, ry, rz));
goto CLEANUP;
}
if (mp_cmp_d(pz, 1) == 0) {
/* M = 3 * px^2 + a */
MP_CHECKOK(group->meth->field_sqr(px, &t0, group->meth));
MP_CHECKOK(group->meth->field_add(&t0, &t0, &M, group->meth));
MP_CHECKOK(group->meth->field_add(&t0, &M, &t0, group->meth));
MP_CHECKOK(group->meth->
field_add(&t0, &group->curvea, &M, group->meth));
} else if (MP_SIGN(&group->curvea) == MP_NEG &&
MP_USED(&group->curvea) == 1 &&
MP_DIGIT(&group->curvea, 0) == 3) {
/* M = 3 * (px + pz^2) * (px - pz^2) */
MP_CHECKOK(group->meth->field_sqr(pz, &M, group->meth));
MP_CHECKOK(group->meth->field_add(px, &M, &t0, group->meth));
MP_CHECKOK(group->meth->field_sub(px, &M, &t1, group->meth));
MP_CHECKOK(group->meth->field_mul(&t0, &t1, &M, group->meth));
MP_CHECKOK(group->meth->field_add(&M, &M, &t0, group->meth));
MP_CHECKOK(group->meth->field_add(&t0, &M, &M, group->meth));
} else {
/* M = 3 * (px^2) + a * (pz^4) */
MP_CHECKOK(group->meth->field_sqr(px, &t0, group->meth));
MP_CHECKOK(group->meth->field_add(&t0, &t0, &M, group->meth));
MP_CHECKOK(group->meth->field_add(&t0, &M, &t0, group->meth));
MP_CHECKOK(group->meth->field_sqr(pz, &M, group->meth));
MP_CHECKOK(group->meth->field_sqr(&M, &M, group->meth));
MP_CHECKOK(group->meth->
field_mul(&M, &group->curvea, &M, group->meth));
MP_CHECKOK(group->meth->field_add(&M, &t0, &M, group->meth));
}
/* rz = 2 * py * pz */
/* t0 = 4 * py^2 */
if (mp_cmp_d(pz, 1) == 0) {
MP_CHECKOK(group->meth->field_add(py, py, rz, group->meth));
MP_CHECKOK(group->meth->field_sqr(rz, &t0, group->meth));
} else {
MP_CHECKOK(group->meth->field_add(py, py, &t0, group->meth));
MP_CHECKOK(group->meth->field_mul(&t0, pz, rz, group->meth));
MP_CHECKOK(group->meth->field_sqr(&t0, &t0, group->meth));
}
/* S = 4 * px * py^2 = px * (2 * py)^2 */
MP_CHECKOK(group->meth->field_mul(px, &t0, &S, group->meth));
/* rx = M^2 - 2 * S */
MP_CHECKOK(group->meth->field_add(&S, &S, &t1, group->meth));
MP_CHECKOK(group->meth->field_sqr(&M, rx, group->meth));
MP_CHECKOK(group->meth->field_sub(rx, &t1, rx, group->meth));
/* ry = M * (S - rx) - 8 * py^4 */
MP_CHECKOK(group->meth->field_sqr(&t0, &t1, group->meth));
if (mp_isodd(&t1)) {
MP_CHECKOK(mp_add(&t1, &group->meth->irr, &t1));
}
MP_CHECKOK(mp_div_2(&t1, &t1));
MP_CHECKOK(group->meth->field_sub(&S, rx, &S, group->meth));
MP_CHECKOK(group->meth->field_mul(&M, &S, &M, group->meth));
MP_CHECKOK(group->meth->field_sub(&M, &t1, ry, group->meth));
CLEANUP:
mp_clear(&t0);
mp_clear(&t1);
mp_clear(&M);
mp_clear(&S);
return res;
}
/**
Create DSA parameters (INTERNAL ONLY, not part of public API)
@param prng An active PRNG state
@param wprng The index of the PRNG desired
@param group_size Size of the multiplicative group (octets)
@param modulus_size Size of the modulus (octets)
@param p [out] bignum where generated 'p' is stored (must be initialized by caller)
@param q [out] bignum where generated 'q' is stored (must be initialized by caller)
@param g [out] bignum where generated 'g' is stored (must be initialized by caller)
@return CRYPT_OK if successful, upon error this function will free all allocated memory
*/
static int _dsa_make_params(prng_state *prng, int wprng, int group_size, int modulus_size, void *p, void *q, void *g)
{
unsigned long L, N, n, outbytes, seedbytes, counter, j, i;
int err, res, mr_tests_q, mr_tests_p, found_p, found_q, hash;
unsigned char *wbuf, *sbuf, digest[MAXBLOCKSIZE];
void *t2L1, *t2N1, *t2q, *t2seedlen, *U, *W, *X, *c, *h, *e, *seedinc;
/* check size */
if (group_size >= LTC_MDSA_MAX_GROUP || group_size < 1 || group_size >= modulus_size) {
return CRYPT_INVALID_ARG;
}
/* FIPS-186-4 A.1.1.2 Generation of the Probable Primes p and q Using an Approved Hash Function
*
* L = The desired length of the prime p (in bits e.g. L = 1024)
* N = The desired length of the prime q (in bits e.g. N = 160)
* seedlen = The desired bit length of the domain parameter seed; seedlen shallbe equal to or greater than N
* outlen = The bit length of Hash function
*
* 1. Check that the (L, N)
* 2. If (seedlen <N), then return INVALID.
* 3. n = ceil(L / outlen) - 1
* 4. b = L- 1 - (n * outlen)
* 5. domain_parameter_seed = an arbitrary sequence of seedlen bits
* 6. U = Hash (domain_parameter_seed) mod 2^(N-1)
* 7. q = 2^(N-1) + U + 1 - (U mod 2)
* 8. Test whether or not q is prime as specified in Appendix C.3
* 9. If qis not a prime, then go to step 5.
* 10. offset = 1
* 11. For counter = 0 to (4L- 1) do {
* For j=0 to n do {
* Vj = Hash ((domain_parameter_seed+ offset + j) mod 2^seedlen
* }
* W = V0 + (V1 *2^outlen) + ... + (Vn-1 * 2^((n-1) * outlen)) + ((Vn mod 2^b) * 2^(n * outlen))
* X = W + 2^(L-1) Comment: 0 <= W < 2^(L-1); hence 2^(L-1) <= X < 2^L
* c = X mod 2*q
* p = X - (c - 1) Comment: p ~ 1 (mod 2*q)
* If (p >= 2^(L-1)) {
* Test whether or not p is prime as specified in Appendix C.3.
* If p is determined to be prime, then return VALID and the values of p, qand (optionally) the values of domain_parameter_seed and counter
* }
* offset = offset + n + 1 Comment: Increment offset
* }
*/
seedbytes = group_size;
L = (unsigned long)modulus_size * 8;
N = (unsigned long)group_size * 8;
/* XXX-TODO no Lucas test */
#ifdef LTC_MPI_HAS_LUCAS_TEST
/* M-R tests (when followed by one Lucas test) according FIPS-186-4 - Appendix C.3 - table C.1 */
mr_tests_p = (L <= 2048) ? 3 : 2;
if (N <= 160) { mr_tests_q = 19; }
else if (N <= 224) { mr_tests_q = 24; }
else { mr_tests_q = 27; }
#else
/* M-R tests (without Lucas test) according FIPS-186-4 - Appendix C.3 - table C.1 */
if (L <= 1024) { mr_tests_p = 40; }
else if (L <= 2048) { mr_tests_p = 56; }
else { mr_tests_p = 64; }
if (N <= 160) { mr_tests_q = 40; }
else if (N <= 224) { mr_tests_q = 56; }
else { mr_tests_q = 64; }
#endif
if (N <= 256) {
hash = register_hash(&sha256_desc);
}
else if (N <= 384) {
hash = register_hash(&sha384_desc);
}
else if (N <= 512) {
hash = register_hash(&sha512_desc);
}
else {
return CRYPT_INVALID_ARG; /* group_size too big */
}
if ((err = hash_is_valid(hash)) != CRYPT_OK) { return err; }
outbytes = hash_descriptor[hash].hashsize;
n = ((L + outbytes*8 - 1) / (outbytes*8)) - 1;
if ((wbuf = XMALLOC((n+1)*outbytes)) == NULL) { err = CRYPT_MEM; goto cleanup3; }
if ((sbuf = XMALLOC(seedbytes)) == NULL) { err = CRYPT_MEM; goto cleanup2; }
err = mp_init_multi(&t2L1, &t2N1, &t2q, &t2seedlen, &U, &W, &X, &c, &h, &e, &seedinc, NULL);
if (err != CRYPT_OK) { goto cleanup1; }
if ((err = mp_2expt(t2L1, L-1)) != CRYPT_OK) { goto cleanup; }
/* t2L1 = 2^(L-1) */
if ((err = mp_2expt(t2N1, N-1)) != CRYPT_OK) { goto cleanup; }
/* t2N1 = 2^(N-1) */
if ((err = mp_2expt(t2seedlen, seedbytes*8)) != CRYPT_OK) { goto cleanup; }
/* t2seedlen = 2^seedlen */
for(found_p=0; !found_p;) {
/* q */
for(found_q=0; !found_q;) {
if (prng_descriptor[wprng].read(sbuf, seedbytes, prng) != seedbytes) { err = CRYPT_ERROR_READPRNG; goto cleanup; }
i = outbytes;
if ((err = hash_memory(hash, sbuf, seedbytes, digest, &i)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_read_unsigned_bin(U, digest, outbytes)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_mod(U, t2N1, U)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_add(t2N1, U, q)) != CRYPT_OK) { goto cleanup; }
if (!mp_isodd(q)) mp_add_d(q, 1, q);
if ((err = mp_prime_is_prime(q, mr_tests_q, &res)) != CRYPT_OK) { goto cleanup; }
if (res == LTC_MP_YES) found_q = 1;
}
/* p */
if ((err = mp_read_unsigned_bin(seedinc, sbuf, seedbytes)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_add(q, q, t2q)) != CRYPT_OK) { goto cleanup; }
for(counter=0; counter < 4*L && !found_p; counter++) {
for(j=0; j<=n; j++) {
if ((err = mp_add_d(seedinc, 1, seedinc)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_mod(seedinc, t2seedlen, seedinc)) != CRYPT_OK) { goto cleanup; }
/* seedinc = (seedinc+1) % 2^seed_bitlen */
if ((i = mp_unsigned_bin_size(seedinc)) > seedbytes) { err = CRYPT_INVALID_ARG; goto cleanup; }
zeromem(sbuf, seedbytes);
if ((err = mp_to_unsigned_bin(seedinc, sbuf + seedbytes-i)) != CRYPT_OK) { goto cleanup; }
i = outbytes;
err = hash_memory(hash, sbuf, seedbytes, wbuf+(n-j)*outbytes, &i);
if (err != CRYPT_OK) { goto cleanup; }
}
if ((err = mp_read_unsigned_bin(W, wbuf, (n+1)*outbytes)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_mod(W, t2L1, W)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_add(W, t2L1, X)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_mod(X, t2q, c)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_sub_d(c, 1, p)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_sub(X, p, p)) != CRYPT_OK) { goto cleanup; }
if (mp_cmp(p, t2L1) != LTC_MP_LT) {
/* p >= 2^(L-1) */
if ((err = mp_prime_is_prime(p, mr_tests_p, &res)) != CRYPT_OK) { goto cleanup; }
if (res == LTC_MP_YES) {
found_p = 1;
}
}
}
}
/* FIPS-186-4 A.2.1 Unverifiable Generation of the Generator g
* 1. e = (p - 1)/q
* 2. h = any integer satisfying: 1 < h < (p - 1)
* h could be obtained from a random number generator or from a counter that changes after each use
* 3. g = h^e mod p
* 4. if (g == 1), then go to step 2.
*
*/
if ((err = mp_sub_d(p, 1, e)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_div(e, q, e, c)) != CRYPT_OK) { goto cleanup; }
/* e = (p - 1)/q */
i = mp_count_bits(p);
do {
do {
if ((err = rand_bn_bits(h, i, prng, wprng)) != CRYPT_OK) { goto cleanup; }
} while (mp_cmp(h, p) != LTC_MP_LT || mp_cmp_d(h, 2) != LTC_MP_GT);
if ((err = mp_sub_d(h, 1, h)) != CRYPT_OK) { goto cleanup; }
/* h is randon and 1 < h < (p-1) */
if ((err = mp_exptmod(h, e, p, g)) != CRYPT_OK) { goto cleanup; }
} while (mp_cmp_d(g, 1) == LTC_MP_EQ);
err = CRYPT_OK;
cleanup:
mp_clear_multi(t2L1, t2N1, t2q, t2seedlen, U, W, X, c, h, e, seedinc, NULL);
cleanup1:
XFREE(sbuf);
cleanup2:
XFREE(wbuf);
cleanup3:
return err;
}
/* computes the modular inverse via binary extended euclidean algorithm,
* that is c = 1/a mod b
*
* Based on slow invmod except this is optimized for the case where b is
* odd as per HAC Note 14.64 on pp. 610
*/
int fast_mp_invmod (mp_int * a, mp_int * b, mp_int * c)
{
mp_int x, y, u, v, B, D;
int res, neg;
/* 2. [modified] b must be odd */
if (mp_iseven (b) == 1) {
return MP_VAL;
}
/* init all our temps */
if ((res = mp_init_multi(&x, &y, &u, &v, &B, &D, NULL)) != MP_OKAY) {
return res;
}
/* x == modulus, y == value to invert */
if ((res = mp_copy (b, &x)) != MP_OKAY) {
goto LBL_ERR;
}
/* we need y = |a| */
if ((res = mp_mod (a, b, &y)) != MP_OKAY) {
goto LBL_ERR;
}
/* 3. u=x, v=y, A=1, B=0, C=0,D=1 */
if ((res = mp_copy (&x, &u)) != MP_OKAY) {
goto LBL_ERR;
}
if ((res = mp_copy (&y, &v)) != MP_OKAY) {
goto LBL_ERR;
}
mp_set (&D, 1);
top:
/* 4. while u is even do */
while (mp_iseven (&u) == 1) {
/* 4.1 u = u/2 */
if ((res = mp_div_2 (&u, &u)) != MP_OKAY) {
goto LBL_ERR;
}
/* 4.2 if B is odd then */
if (mp_isodd (&B) == 1) {
if ((res = mp_sub (&B, &x, &B)) != MP_OKAY) {
goto LBL_ERR;
}
}
/* B = B/2 */
if ((res = mp_div_2 (&B, &B)) != MP_OKAY) {
goto LBL_ERR;
}
}
/* 5. while v is even do */
while (mp_iseven (&v) == 1) {
/* 5.1 v = v/2 */
if ((res = mp_div_2 (&v, &v)) != MP_OKAY) {
goto LBL_ERR;
}
/* 5.2 if D is odd then */
if (mp_isodd (&D) == 1) {
/* D = (D-x)/2 */
if ((res = mp_sub (&D, &x, &D)) != MP_OKAY) {
goto LBL_ERR;
}
}
/* D = D/2 */
if ((res = mp_div_2 (&D, &D)) != MP_OKAY) {
goto LBL_ERR;
}
}
/* 6. if u >= v then */
if (mp_cmp (&u, &v) != MP_LT) {
/* u = u - v, B = B - D */
if ((res = mp_sub (&u, &v, &u)) != MP_OKAY) {
goto LBL_ERR;
}
if ((res = mp_sub (&B, &D, &B)) != MP_OKAY) {
goto LBL_ERR;
}
} else {
/* v - v - u, D = D - B */
if ((res = mp_sub (&v, &u, &v)) != MP_OKAY) {
goto LBL_ERR;
}
if ((res = mp_sub (&D, &B, &D)) != MP_OKAY) {
goto LBL_ERR;
}
}
/* if not zero goto step 4 */
if (mp_iszero (&u) == 0) {
goto top;
}
/* now a = C, b = D, gcd == g*v */
/* if v != 1 then there is no inverse */
if (mp_cmp_d (&v, 1) != MP_EQ) {
res = MP_VAL;
goto LBL_ERR;
}
/* b is now the inverse */
neg = a->sign;
while (D.sign == MP_NEG) {
if ((res = mp_add (&D, b, &D)) != MP_OKAY) {
goto LBL_ERR;
}
}
mp_exch (&D, c);
c->sign = neg;
res = MP_OKAY;
LBL_ERR:mp_clear_multi (&x, &y, &u, &v, &B, &D, NULL);
return res;
}
/* Greatest Common Divisor using the binary method [Algorithm B, page 338, vol2 of TAOCP]
*/
int
mp_gcd (mp_int * a, mp_int * b, mp_int * c)
{
mp_int u, v, t;
int k, res, neg;
/* either zero than gcd is the largest */
if (mp_iszero (a) == 1 && mp_iszero (b) == 0) {
return mp_copy (b, c);
}
if (mp_iszero (a) == 0 && mp_iszero (b) == 1) {
return mp_copy (a, c);
}
if (mp_iszero (a) == 1 && mp_iszero (b) == 1) {
mp_set (c, 1);
return MP_OKAY;
}
/* if both are negative they share (-1) as a common divisor */
neg = (a->sign == b->sign) ? a->sign : MP_ZPOS;
if ((res = mp_init_copy (&u, a)) != MP_OKAY) {
return res;
}
if ((res = mp_init_copy (&v, b)) != MP_OKAY) {
goto __U;
}
/* must be positive for the remainder of the algorithm */
u.sign = v.sign = MP_ZPOS;
if ((res = mp_init (&t)) != MP_OKAY) {
goto __V;
}
/* B1. Find power of two */
k = 0;
while (mp_iseven(&u) == 1 && mp_iseven(&v) == 1) {
++k;
if ((res = mp_div_2 (&u, &u)) != MP_OKAY) {
goto __T;
}
if ((res = mp_div_2 (&v, &v)) != MP_OKAY) {
goto __T;
}
}
/* B2. Initialize */
if (mp_isodd(&u) == 1) {
/* t = -v */
if ((res = mp_copy (&v, &t)) != MP_OKAY) {
goto __T;
}
t.sign = MP_NEG;
} else {
/* t = u */
if ((res = mp_copy (&u, &t)) != MP_OKAY) {
goto __T;
}
}
do {
/* B3 (and B4). Halve t, if even */
while (t.used != 0 && mp_iseven(&t) == 1) {
if ((res = mp_div_2 (&t, &t)) != MP_OKAY) {
goto __T;
}
}
/* B5. if t>0 then u=t otherwise v=-t */
if (t.used != 0 && t.sign != MP_NEG) {
if ((res = mp_copy (&t, &u)) != MP_OKAY) {
goto __T;
}
} else {
if ((res = mp_copy (&t, &v)) != MP_OKAY) {
goto __T;
}
v.sign = (v.sign == MP_ZPOS) ? MP_NEG : MP_ZPOS;
}
/* B6. t = u - v, if t != 0 loop otherwise terminate */
if ((res = mp_sub (&u, &v, &t)) != MP_OKAY) {
goto __T;
}
} while (mp_iszero(&t) == 0);
/* multiply by 2^k which we divided out at the beginning */
if ((res = mp_mul_2d (&u, k, &u)) != MP_OKAY) {
goto __T;
}
mp_exch (&u, c);
c->sign = neg;
res = MP_OKAY;
__T:
mp_clear (&t);
__V:
mp_clear (&u);
__U:
mp_clear (&v);
return res;
}
mp_err mp_exptmod(const mp_int *inBase, const mp_int *exponent,
const mp_int *modulus, mp_int *result)
{
const mp_int *base;
mp_size bits_in_exponent, i, window_bits, odd_ints;
mp_err res;
int nLen;
mp_int montBase, goodBase;
mp_mont_modulus mmm;
#ifdef MP_USING_CACHE_SAFE_MOD_EXP
static unsigned int max_window_bits;
#endif
/* function for computing n0prime only works if n0 is odd */
if (!mp_isodd(modulus))
return s_mp_exptmod(inBase, exponent, modulus, result);
MP_DIGITS(&montBase) = 0;
MP_DIGITS(&goodBase) = 0;
if (mp_cmp(inBase, modulus) < 0) {
base = inBase;
} else {
MP_CHECKOK( mp_init(&goodBase) );
base = &goodBase;
MP_CHECKOK( mp_mod(inBase, modulus, &goodBase) );
}
nLen = MP_USED(modulus);
MP_CHECKOK( mp_init_size(&montBase, 2 * nLen + 2) );
mmm.N = *modulus; /* a copy of the mp_int struct */
/* compute n0', given n0, n0' = -(n0 ** -1) mod MP_RADIX
** where n0 = least significant mp_digit of N, the modulus.
*/
mmm.n0prime = 0 - s_mp_invmod_radix( MP_DIGIT(modulus, 0) );
MP_CHECKOK( s_mp_to_mont(base, &mmm, &montBase) );
bits_in_exponent = mpl_significant_bits(exponent);
#ifdef MP_USING_CACHE_SAFE_MOD_EXP
if (mp_using_cache_safe_exp) {
if (bits_in_exponent > 780)
window_bits = 6;
else if (bits_in_exponent > 256)
window_bits = 5;
else if (bits_in_exponent > 20)
window_bits = 4;
/* RSA public key exponents are typically under 20 bits (common values
* are: 3, 17, 65537) and a 4-bit window is inefficient
*/
else
window_bits = 1;
} else
#endif
if (bits_in_exponent > 480)
window_bits = 6;
else if (bits_in_exponent > 160)
window_bits = 5;
else if (bits_in_exponent > 20)
window_bits = 4;
/* RSA public key exponents are typically under 20 bits (common values
* are: 3, 17, 65537) and a 4-bit window is inefficient
*/
else
window_bits = 1;
#ifdef MP_USING_CACHE_SAFE_MOD_EXP
/*
* clamp the window size based on
* the cache line size.
*/
if (!max_window_bits) {
unsigned long cache_size = s_mpi_getProcessorLineSize();
/* processor has no cache, use 'fast' code always */
if (cache_size == 0) {
mp_using_cache_safe_exp = 0;
}
if ((cache_size == 0) || (cache_size >= 64)) {
max_window_bits = 6;
} else if (cache_size >= 32) {
max_window_bits = 5;
} else if (cache_size >= 16) {
max_window_bits = 4;
} else max_window_bits = 1; /* should this be an assert? */
}
/* clamp the window size down before we caclulate bits_in_exponent */
if (mp_using_cache_safe_exp) {
if (window_bits > max_window_bits) {
window_bits = max_window_bits;
}
}
#endif
odd_ints = 1 << (window_bits - 1);
i = bits_in_exponent % window_bits;
if (i != 0) {
bits_in_exponent += window_bits - i;
}
#ifdef MP_USING_MONT_MULF
if (mp_using_mont_mulf) {
MP_CHECKOK( s_mp_pad(&montBase, nLen) );
res = mp_exptmod_f(&montBase, exponent, modulus, result, &mmm, nLen,
bits_in_exponent, window_bits, odd_ints);
} else
#endif
#ifdef MP_USING_CACHE_SAFE_MOD_EXP
if (mp_using_cache_safe_exp) {
res = mp_exptmod_safe_i(&montBase, exponent, modulus, result, &mmm, nLen,
bits_in_exponent, window_bits, 1 << window_bits);
} else
#endif
res = mp_exptmod_i(&montBase, exponent, modulus, result, &mmm, nLen,
bits_in_exponent, window_bits, odd_ints);
CLEANUP:
mp_clear(&montBase);
mp_clear(&goodBase);
/* Don't mp_clear mmm.N because it is merely a copy of modulus.
** Just zap it.
*/
memset(&mmm, 0, sizeof mmm);
return res;
}
/*
Strong Lucas-Selfridge test.
returns MP_YES if it is a strong L-S prime, MP_NO if it is composite
Code ported from Thomas Ray Nicely's implementation of the BPSW test
at http://www.trnicely.net/misc/bpsw.html
Freeware copyright (C) 2016 Thomas R. Nicely <http://www.trnicely.net>.
Released into the public domain by the author, who disclaims any legal
liability arising from its use
The multi-line comments are made by Thomas R. Nicely and are copied verbatim.
Additional comments marked "CZ" (without the quotes) are by the code-portist.
(If that name sounds familiar, he is the guy who found the fdiv bug in the
Pentium (P5x, I think) Intel processor)
*/
int mp_prime_strong_lucas_selfridge(const mp_int *a, int *result)
{
/* CZ TODO: choose better variable names! */
mp_int Dz, gcd, Np1, Uz, Vz, U2mz, V2mz, Qmz, Q2mz, Qkdz, T1z, T2z, T3z, T4z, Q2kdz;
/* CZ TODO: Some of them need the full 32 bit, hence the (temporary) exclusion of MP_8BIT */
int32_t D, Ds, J, sign, P, Q, r, s, u, Nbits;
int e;
int isset;
*result = MP_NO;
/*
Find the first element D in the sequence {5, -7, 9, -11, 13, ...}
such that Jacobi(D,N) = -1 (Selfridge's algorithm). Theory
indicates that, if N is not a perfect square, D will "nearly
always" be "small." Just in case, an overflow trap for D is
included.
*/
if ((e = mp_init_multi(&Dz, &gcd, &Np1, &Uz, &Vz, &U2mz, &V2mz, &Qmz, &Q2mz, &Qkdz, &T1z, &T2z, &T3z, &T4z, &Q2kdz,
NULL)) != MP_OKAY) {
return e;
}
D = 5;
sign = 1;
for (;;) {
Ds = sign * D;
sign = -sign;
if ((e = mp_set_long(&Dz, (unsigned long)D)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if ((e = mp_gcd(a, &Dz, &gcd)) != MP_OKAY) {
goto LBL_LS_ERR;
}
/* if 1 < GCD < N then N is composite with factor "D", and
Jacobi(D,N) is technically undefined (but often returned
as zero). */
if ((mp_cmp_d(&gcd, 1uL) == MP_GT) && (mp_cmp(&gcd, a) == MP_LT)) {
goto LBL_LS_ERR;
}
if (Ds < 0) {
Dz.sign = MP_NEG;
}
if ((e = mp_kronecker(&Dz, a, &J)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if (J == -1) {
break;
}
D += 2;
if (D > (INT_MAX - 2)) {
e = MP_VAL;
goto LBL_LS_ERR;
}
}
P = 1; /* Selfridge's choice */
Q = (1 - Ds) / 4; /* Required so D = P*P - 4*Q */
/* NOTE: The conditions (a) N does not divide Q, and
(b) D is square-free or not a perfect square, are included by
some authors; e.g., "Prime numbers and computer methods for
factorization," Hans Riesel (2nd ed., 1994, Birkhauser, Boston),
p. 130. For this particular application of Lucas sequences,
these conditions were found to be immaterial. */
/* Now calculate N - Jacobi(D,N) = N + 1 (even), and calculate the
odd positive integer d and positive integer s for which
N + 1 = 2^s*d (similar to the step for N - 1 in Miller's test).
The strong Lucas-Selfridge test then returns N as a strong
Lucas probable prime (slprp) if any of the following
conditions is met: U_d=0, V_d=0, V_2d=0, V_4d=0, V_8d=0,
V_16d=0, ..., etc., ending with V_{2^(s-1)*d}=V_{(N+1)/2}=0
(all equalities mod N). Thus d is the highest index of U that
must be computed (since V_2m is independent of U), compared
to U_{N+1} for the standard Lucas-Selfridge test; and no
index of V beyond (N+1)/2 is required, just as in the
standard Lucas-Selfridge test. However, the quantity Q^d must
be computed for use (if necessary) in the latter stages of
the test. The result is that the strong Lucas-Selfridge test
has a running time only slightly greater (order of 10 %) than
that of the standard Lucas-Selfridge test, while producing
only (roughly) 30 % as many pseudoprimes (and every strong
Lucas pseudoprime is also a standard Lucas pseudoprime). Thus
the evidence indicates that the strong Lucas-Selfridge test is
more effective than the standard Lucas-Selfridge test, and a
Baillie-PSW test based on the strong Lucas-Selfridge test
should be more reliable. */
if ((e = mp_add_d(a, 1uL, &Np1)) != MP_OKAY) {
goto LBL_LS_ERR;
}
s = mp_cnt_lsb(&Np1);
/* CZ
* This should round towards zero because
* Thomas R. Nicely used GMP's mpz_tdiv_q_2exp()
* and mp_div_2d() is equivalent. Additionally:
* dividing an even number by two does not produce
* any leftovers.
*/
if ((e = mp_div_2d(&Np1, s, &Dz, NULL)) != MP_OKAY) {
goto LBL_LS_ERR;
}
/* We must now compute U_d and V_d. Since d is odd, the accumulated
values U and V are initialized to U_1 and V_1 (if the target
index were even, U and V would be initialized instead to U_0=0
and V_0=2). The values of U_2m and V_2m are also initialized to
U_1 and V_1; the FOR loop calculates in succession U_2 and V_2,
U_4 and V_4, U_8 and V_8, etc. If the corresponding bits
(1, 2, 3, ...) of t are on (the zero bit having been accounted
for in the initialization of U and V), these values are then
combined with the previous totals for U and V, using the
composition formulas for addition of indices. */
mp_set(&Uz, 1uL); /* U=U_1 */
mp_set(&Vz, (mp_digit)P); /* V=V_1 */
mp_set(&U2mz, 1uL); /* U_1 */
mp_set(&V2mz, (mp_digit)P); /* V_1 */
if (Q < 0) {
Q = -Q;
if ((e = mp_set_long(&Qmz, (unsigned long)Q)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if ((e = mp_mul_2(&Qmz, &Q2mz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
/* Initializes calculation of Q^d */
if ((e = mp_set_long(&Qkdz, (unsigned long)Q)) != MP_OKAY) {
goto LBL_LS_ERR;
}
Qmz.sign = MP_NEG;
Q2mz.sign = MP_NEG;
Qkdz.sign = MP_NEG;
Q = -Q;
} else {
if ((e = mp_set_long(&Qmz, (unsigned long)Q)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if ((e = mp_mul_2(&Qmz, &Q2mz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
/* Initializes calculation of Q^d */
if ((e = mp_set_long(&Qkdz, (unsigned long)Q)) != MP_OKAY) {
goto LBL_LS_ERR;
}
}
Nbits = mp_count_bits(&Dz);
for (u = 1; u < Nbits; u++) { /* zero bit off, already accounted for */
/* Formulas for doubling of indices (carried out mod N). Note that
* the indices denoted as "2m" are actually powers of 2, specifically
* 2^(ul-1) beginning each loop and 2^ul ending each loop.
*
* U_2m = U_m*V_m
* V_2m = V_m*V_m - 2*Q^m
*/
if ((e = mp_mul(&U2mz, &V2mz, &U2mz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if ((e = mp_mod(&U2mz, a, &U2mz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if ((e = mp_sqr(&V2mz, &V2mz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if ((e = mp_sub(&V2mz, &Q2mz, &V2mz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if ((e = mp_mod(&V2mz, a, &V2mz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
/* Must calculate powers of Q for use in V_2m, also for Q^d later */
if ((e = mp_sqr(&Qmz, &Qmz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
/* prevents overflow */ /* CZ still necessary without a fixed prealloc'd mem.? */
if ((e = mp_mod(&Qmz, a, &Qmz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if ((e = mp_mul_2(&Qmz, &Q2mz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if ((isset = mp_get_bit(&Dz, u)) == MP_VAL) {
e = isset;
goto LBL_LS_ERR;
}
if (isset == MP_YES) {
/* Formulas for addition of indices (carried out mod N);
*
* U_(m+n) = (U_m*V_n + U_n*V_m)/2
* V_(m+n) = (V_m*V_n + D*U_m*U_n)/2
*
* Be careful with division by 2 (mod N)!
*/
if ((e = mp_mul(&U2mz, &Vz, &T1z)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if ((e = mp_mul(&Uz, &V2mz, &T2z)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if ((e = mp_mul(&V2mz, &Vz, &T3z)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if ((e = mp_mul(&U2mz, &Uz, &T4z)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if ((e = s_mp_mul_si(&T4z, (long)Ds, &T4z)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if ((e = mp_add(&T1z, &T2z, &Uz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if (mp_isodd(&Uz) != MP_NO) {
if ((e = mp_add(&Uz, a, &Uz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
}
/* CZ
* This should round towards negative infinity because
* Thomas R. Nicely used GMP's mpz_fdiv_q_2exp().
* But mp_div_2() does not do so, it is truncating instead.
*/
if ((e = mp_div_2(&Uz, &Uz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if ((Uz.sign == MP_NEG) && (mp_isodd(&Uz) != MP_NO)) {
if ((e = mp_sub_d(&Uz, 1uL, &Uz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
}
if ((e = mp_add(&T3z, &T4z, &Vz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if (mp_isodd(&Vz) != MP_NO) {
if ((e = mp_add(&Vz, a, &Vz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
}
if ((e = mp_div_2(&Vz, &Vz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if ((Vz.sign == MP_NEG) && (mp_isodd(&Vz) != MP_NO)) {
if ((e = mp_sub_d(&Vz, 1uL, &Vz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
}
if ((e = mp_mod(&Uz, a, &Uz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if ((e = mp_mod(&Vz, a, &Vz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
/* Calculating Q^d for later use */
if ((e = mp_mul(&Qkdz, &Qmz, &Qkdz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if ((e = mp_mod(&Qkdz, a, &Qkdz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
}
}
/* If U_d or V_d is congruent to 0 mod N, then N is a prime or a
strong Lucas pseudoprime. */
if ((mp_iszero(&Uz) != MP_NO) || (mp_iszero(&Vz) != MP_NO)) {
*result = MP_YES;
goto LBL_LS_ERR;
}
/* NOTE: Ribenboim ("The new book of prime number records," 3rd ed.,
1995/6) omits the condition V0 on p.142, but includes it on
p. 130. The condition is NECESSARY; otherwise the test will
return false negatives---e.g., the primes 29 and 2000029 will be
returned as composite. */
/* Otherwise, we must compute V_2d, V_4d, V_8d, ..., V_{2^(s-1)*d}
by repeated use of the formula V_2m = V_m*V_m - 2*Q^m. If any of
these are congruent to 0 mod N, then N is a prime or a strong
Lucas pseudoprime. */
/* Initialize 2*Q^(d*2^r) for V_2m */
if ((e = mp_mul_2(&Qkdz, &Q2kdz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
for (r = 1; r < s; r++) {
if ((e = mp_sqr(&Vz, &Vz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if ((e = mp_sub(&Vz, &Q2kdz, &Vz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if ((e = mp_mod(&Vz, a, &Vz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if (mp_iszero(&Vz) != MP_NO) {
*result = MP_YES;
goto LBL_LS_ERR;
}
/* Calculate Q^{d*2^r} for next r (final iteration irrelevant). */
if (r < (s - 1)) {
if ((e = mp_sqr(&Qkdz, &Qkdz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if ((e = mp_mod(&Qkdz, a, &Qkdz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
if ((e = mp_mul_2(&Qkdz, &Q2kdz)) != MP_OKAY) {
goto LBL_LS_ERR;
}
}
}
LBL_LS_ERR:
mp_clear_multi(&Q2kdz, &T4z, &T3z, &T2z, &T1z, &Qkdz, &Q2mz, &Qmz, &V2mz, &U2mz, &Vz, &Uz, &Np1, &gcd, &Dz, NULL);
return e;
}
