oracle 8.1.6 encryp/decrypt help ??

hi all -I have a linuxbox with oracle 8.1.6 databse installed -I have 2 store function to encrypt and decrypt as follow : encrypt function (input_string varchar2, key_string varchar2) return varchar2 is encrypt_string varchar2(2048); begin sys.dbms_obfuscation_toolkit.DesEncrypt(input_string =>input_string, key_string =>key_string, encrypted_string =>encrypt_string); return encrypt_string; end; decrypt function (encrypt_string_cc varchar2, key_string varchar2) return varchar2 is decrypt_string_cc varchar2(2048); begin sys.dbms_obfuscation_toolkit.DesDecrypt(input_string =>encrypt_string_cc, key_string =>key_string, decrypted_string =>decrypt_string_cc); return decrypt_string_cc; end; and my simple php script like this : $sql = "select encrypt_cc('1234567890123456', 'minh nguyen van') ENCRYPT from dual"; print $sql."<br>"; $stmt=ociparse($conn, $sql); ociexecute($stmt, oci_default); ocifetch($stmt); $encypt = ociresult($stmt,"ENCRYPT"); print "encrypt value -->".$encypt."<--<br>"; $sql = "select encrypt_cc('".$encypt."', 'minh nguyen van') ENCRYPT from dual"; print $sql."<br>"; $stmt=ociparse($conn, $sql); ociexecute($stmt, oci_default); ocifetch($stmt); $encypt = ociresult($stmt,"ENCRYPT"); print "deencrypt value -->".$encypt."<--"; but the result return is quite diffrent one with the original any ideas are helpfull Regards m