I'm going to wrap database trigger's source code, command properly run but source not encrypt

I'm going to wrap my source of database logon trigger. i run the command, "wrap iname='E:\block_tools_trigger_HR.sql' oname='E:\block_tools_trigger_HR.plb'". plb file created without any error but code not encrypted. Source code of trigger is given blow: CREATE OR REPLACE TRIGGER block_tools_trigger_HR AFTER LOGON ON HRMS.SCHEMA DECLARE v_prog sys.v_$session.program%TYPE; BEGIN SELECT upper(program) INTO v_prog FROM sys.v_$session WHERE audsid = USERENV('SESSIONID') AND audsid != 0 AND ROWNUM = 1; IF UPPER(USERENV('TERMINAL')) NOT IN ('MOAZZAM-LT') THEN IF UPPER(v_prog) LIKE '%TOAD%' OR UPPER(v_prog) LIKE '%T.O.A.D%' OR --OR — Toad UPPER(v_prog) LIKE '%SQLNAV%' OR -- — SQL Navigator UPPER(v_prog) LIKE '%PLSQLDEV%' OR --— PLSQL Developer UPPER(v_prog) LIKE '%BUSOBJ%' OR -- — Business Objects UPPER(v_prog) LIKE '%EXCEL%' OR -- — MS-Excel plug-in UPPER(v_prog) LIKE '%SQLPLUS%' OR -- — SQLPLUS UPPER(v_prog) LIKE '%FRMBLD%' OR UPPER(v_prog) LIKE '%IFBLD60%' or upper(v_prog) is null THEN RAISE_APPLICATION_ERROR(-20983, 'You are not allowed to login in '||v_prog); END IF; END IF; END;