/*
* Perform a deterministic walk on the curve, by starting from |point| and
* using the X-coordinate of the previous point as the next scalar for
* point multiplication.
* Returns the X-coordinate of the end result or NULL on error.
*/
static BIGNUM *walk_curve(const EC_GROUP *group, EC_POINT *point, intmax_t num)
{
BIGNUM *scalar = NULL;
intmax_t i;
if (!TEST_ptr(scalar = BN_new())
|| !TEST_true(EC_POINT_get_affine_coordinates(group, point, scalar,
NULL, NULL)))
goto err;
for (i = 0; i < num; i++) {
if (!TEST_true(EC_POINT_mul(group, point, NULL, point, scalar, NULL))
|| !TEST_true(EC_POINT_get_affine_coordinates(group, point,
scalar,
NULL, NULL)))
goto err;
}
return scalar;
err:
BN_free(scalar);
return NULL;
}
int ec_GFp_simple_make_affine(const EC_GROUP *group, EC_POINT *point,
BN_CTX *ctx)
{
BN_CTX *new_ctx = NULL;
BIGNUM *x, *y;
int ret = 0;
if (point->Z_is_one || EC_POINT_is_at_infinity(group, point))
return 1;
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL)
return 0;
}
BN_CTX_start(ctx);
x = BN_CTX_get(ctx);
y = BN_CTX_get(ctx);
if (y == NULL)
goto err;
if (!EC_POINT_get_affine_coordinates(group, point, x, y, ctx))
goto err;
if (!EC_POINT_set_affine_coordinates(group, point, x, y, ctx))
goto err;
if (!point->Z_is_one) {
ECerr(EC_F_EC_GFP_SIMPLE_MAKE_AFFINE, ERR_R_INTERNAL_ERROR);
goto err;
}
ret = 1;
err:
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
return ret;
}
int EC_POINT_get_affine_coordinates_GF2m(const EC_GROUP *group,
const EC_POINT *point, BIGNUM *x,
BIGNUM *y, BN_CTX *ctx)
{
return EC_POINT_get_affine_coordinates(group, point, x, y, ctx);
}
