Haris's example shows use of the procedures without output. I think he could have made the example a little more useful by showing it actually working.
10g improves the encryption and decryption possibilities in the database by providing the DBMS_CRYPTO package that supports more algorithms including AES and also manages the padding better. This new package will replace DBMS_OBFUSCATION_TOOLKIT. There are commercial alternatives as well as free ones to the Oracle provided packages. Details of which can be found on my tools page. Haris's example is worth looking at if you are contemplating use of this package as it shows a simple example.