Make ec_GFp_simple_point_get_affine_coordinates() faster
authorBodo Möller <bodo@openssl.org>
Wed, 20 Nov 2002 10:53:33 +0000 (10:53 +0000)
committerBodo Möller <bodo@openssl.org>
Wed, 20 Nov 2002 10:53:33 +0000 (10:53 +0000)
for Montgomery representations.

Submitted by: Sheueling Chang, Bodo Moeller

crypto/ec/ecp_smpl.c

index ad95b03..7325abf 100644 (file)
@@ -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 (x != NULL)
+               if (group->meth->field_decode)
                        {
-                       if (!BN_copy(x, X_)) goto err;
+                       if (x != NULL)
+                               {
+                               if (!group->meth->field_decode(group, x, &point->X, ctx)) goto err;
+                               }
+                       if (y != NULL)
+                               {
+                               if (!group->meth->field_decode(group, y, &point->Y, ctx)) goto err;
+                               }
                        }
-               if (y != NULL)
+               else
                        {
-                       if (!BN_copy(y, Y_)) goto err;
+                       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;
                        }
                }