July 15 (Reuters) - Federal Reserve Chair Jerome Powell on Thursday said he had not made up his own mind on the merits or demerits of a central bank digital currency, but he would want authorization from Congress before taking any action to create one. “I am legitimately undecided on whether the benefits outweigh the costs or vice versa,” Powell said during a hearing before the Senate Banking Committee. If the Fed were to issue its own digital currency, he said, “we would want very broad support in society and in Congress and ideally that would take the form of authorizing legislation as opposed to a very careful reading of ambiguous law.” (Reporting by Ann Saphir Editing by Chizu Nomiyama)