Criptografia

Código:

declare   function digest( p_username in varchar2, p_password in varchar2 ) return varchar2   is   begin     return ltrim( to_char( dbms_utility.get_hash_value(       upper(p_username)||'/'||upper(p_password),       1000000000,       power(2,30) ),       rpad( 'X',29,'X')||'X' ) );   end digest; begin   for x in ( select username from all_users where rownum < 20 )   loop     dbms_output.put_line( 'User: ' || rpad( x.username , 30 ) ||                           ' digest: ' || digest( x.username, 'TIGER' )     );   end loop; end; / User: SYS                            digest: 6869FA1A User: SYSTEM                         digest: 79F08AFC User: OUTLN                          digest: 5ABFB255 User: DBSNMP                         digest: 43415F6B User: TRACESVR                       digest: 49CF26F6 User: CTXSYS                         digest: 4910C297 User: OEM                            digest: 69463BC2 User: ORDSYS                         digest: 6F048B2B User: ORDPLUGINS                     digest: 6547459C User: MDSYS                          digest: 43C0B367 User: AURORA$ORB$UNAUTHENTICATED     digest: 5073BBFC User: WEB$CDEJESUS                   digest: 6FB5CDB6 User: SCOTT                          digest: 4307767C User: WEB$SMAYFIEL                   digest: 71ED5065 User: UTILS                          digest: 5B7912B7 User: OAS_PUBLIC                     digest: 502BAE3A User: WEBDB                          digest: 5A7AC149 User: WEB$RDRISCOL                   digest: 3E72D3F6 User: WEB$KWARREN                    digest: 7123F5A1 PL/SQL procedure successfully completed.

Agora, se você quer criptografar E descriptografar informações (por exemplo, a coluna de salários dos funcionários). Daí você pode usar uma DBMS do oracle. A Obfuscation toolkit. Este exemplo também foi tirado do asktom...
http://asktom.oracle.com/pls/ask/f?p=4950:8:::::F4950_P8_DISPLAYID:791026226790

Código:

ops$tkyte@DEV816> variable x varchar2(25) ops$tkyte@DEV816> ops$tkyte@DEV816> exec :x := 'How Now Brown Cow'; PL/SQL procedure successfully completed. ops$tkyte@DEV816> ops$tkyte@DEV816> declare   2      l_data  varchar2(255);   3  begin   4      l_data := rpad( :x, (trunc(length(:x)/8)+1)*8, chr(0) );   5    6      dbms_obfuscation_toolkit.DESEncrypt   7          ( input_string => l_data,   8        key_string   => 'MagicKey',   9        encrypted_string=> :x ); 10  end; 11  / PL/SQL procedure successfully completed. ops$tkyte@DEV816> ops$tkyte@DEV816> print x X ------------------------- Òr=ðÝw]ð‘SWñ:ÝÐôÊ?T¬ ops$tkyte@DEV816> ops$tkyte@DEV816> declare   2      l_data  varchar2(255);   3  begin   4      dbms_obfuscation_toolkit.DESDecrypt   5          ( input_string => :x,   6        key_string   => 'MagicKey',   7        decrypted_string=> l_data );   8    9      :x := rtrim( l_data, chr(0) ); 10  end; 11  / PL/SQL procedure successfully completed. ops$tkyte@DEV816> ops$tkyte@DEV816> print x X ------------------------- How Now Brown Cow

A "MagicKey" que você deve criar a sua própria. Se alguém descobrir, conseguirá descriptografar sua informação. Por isso, o ideal é criptografar a sua procedure com o WRAP.