+ BN_CTX *ctx;
+ BIGNUM *order, *u1, *u2, *m, *X;
+ EC_POINT *point = NULL;
+ const EC_GROUP *group;
+ const EC_POINT *pub_key;
+
+ /* check input values */
+ if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
+ (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL)