 supported by the library. The curve name is returned as a <b>NID</b> if it matches. If the group&#39;s domain parameters have been modified then no match will be found. If the curve name of the given group is <b>NID_undef</b> (e.g. it has been created by using explicit parameters with no curve name), then this method can be used to lookup the name of the curve that matches the group domain parameters. The built-in curves contain aliases, so that multiple NID&#39;s can map to the same domain parameters. For