Commit 13744514 authored by Bodo Möller's avatar Bodo Möller
Browse files

Make ec_GFp_simple_point_get_affine_coordinates() faster 

for Montgomery representations.

Submitted by: Sheueling Chang, Bodo Moeller
parent 6a8afe22

crypto/ec/ecp_smpl.c

+26 −25
Original line number Diff line number Diff line
@@ -505,8 +505,8 @@ int ec_GFp_simple_point_get_affine_coordinates(const EC_GROUP *group, const EC_P 
	BIGNUM *x, BIGNUM *y, BN_CTX *ctx)

	{

	BN_CTX *new_ctx = NULL;

	BIGNUM *X, *Y, *Z, *Z_1, *Z_2, *Z_3;

	const BIGNUM *X_, *Y_, *Z_;

	BIGNUM *Z, *Z_1, *Z_2, *Z_3;

	const BIGNUM *Z_;

	int ret = 0;



	if (EC_POINT_is_at_infinity(group, point))
@@ -523,8 +523,6 @@ int ec_GFp_simple_point_get_affine_coordinates(const EC_GROUP *group, const EC_P 
		}



	BN_CTX_start(ctx);

	X = BN_CTX_get(ctx);

	Y = BN_CTX_get(ctx);

	Z = BN_CTX_get(ctx);

	Z_1 = BN_CTX_get(ctx);

	Z_2 = BN_CTX_get(ctx);
@@ -535,27 +533,37 @@ int ec_GFp_simple_point_get_affine_coordinates(const EC_GROUP *group, const EC_P 
	

	if (group->meth->field_decode)

		{

		if (!group->meth->field_decode(group, X, &point->X, ctx)) goto err;

		if (!group->meth->field_decode(group, Y, &point->Y, ctx)) goto err;

		if (!group->meth->field_decode(group, Z, &point->Z, ctx)) goto err;

		X_ = X; Y_ = Y;	Z_ = Z;

		Z_ = Z;

		}

	else

		{

		X_ = &point->X;

		Y_ = &point->Y;

		Z_ = &point->Z;

		}

	

	if (BN_is_one(Z_))

		{

		if (group->meth->field_decode)

			{

			if (x != NULL)

				{

			if (!BN_copy(x, X_)) goto err;

				if (!group->meth->field_decode(group, x, &point->X, ctx)) goto err;

				}

			if (y != NULL)

				{

			if (!BN_copy(y, Y_)) goto err;

				if (!group->meth->field_decode(group, y, &point->Y, ctx)) goto err;

				}

			}

		else

			{

			if (x != NULL)

				{

				if (!BN_copy(x, &point->X)) goto err;

				}

			if (y != NULL)

				{

				if (!BN_copy(y, &point->Y)) goto err;

				}

			}

		}

	else
@@ -578,15 +586,8 @@ int ec_GFp_simple_point_get_affine_coordinates(const EC_GROUP *group, const EC_P 
	

		if (x != NULL)

			{

			if (group->meth->field_encode == 0)

				{

				/* field_mul works on standard representation */

				if (!group->meth->field_mul(group, x, X_, Z_2, ctx)) goto err;

				}

			else

				{

				if (!BN_mod_mul(x, X_, Z_2, &group->field, ctx)) goto err;

				}

			/* in the Montgomery case, field_mul will cancel out Montgomery factor in X: */

			if (!group->meth->field_mul(group, x, &point->X, Z_2, ctx)) goto err;

			}



		if (y != NULL)
@@ -595,14 +596,14 @@ int ec_GFp_simple_point_get_affine_coordinates(const EC_GROUP *group, const EC_P 
				{

				/* field_mul works on standard representation */

				if (!group->meth->field_mul(group, Z_3, Z_2, Z_1, ctx)) goto err;

				if (!group->meth->field_mul(group, y, Y_, Z_3, ctx)) goto err;

				

				}

			else

				{

				if (!BN_mod_mul(Z_3, Z_2, Z_1, &group->field, ctx)) goto err;

				if (!BN_mod_mul(y, Y_, Z_3, &group->field, ctx)) goto err;

				}



			/* in the Montgomery case, field_mul will cancel out Montgomery factor in Y: */

			if (!group->meth->field_mul(group, y, &point->Y, Z_3, ctx)) goto err;

			}

		}