'Verifies files.'

def perform_operation(self, indata, pub_key, cli_args):

    signature_file = cli_args[1]
    with open(signature_file, 'rb') as sigfile:
        signature = sigfile.read()
    try:
        rsa.verify(indata, signature, pub_key)
    except rsa.VerificationError:
        raise SystemExit('Verification    failed.')
    print('Verification    OK', file=sys.stderr)
