How come there is no trigger on select in Oracle

Question

I'm encrypting a value on insert into the table:
insert into table1 (name, ssn) values ('John Smith','123-45-6789');
ssn value gets encrypted and stored either in ssn_enc column or in a separate table on insert trigger.
But now I want to use:
select name, ssn from table1;
And get the decrypted value out. So that's where a select trigger would fit nicely.
Do I really need to complicate it with an overlaying view?
P.S. I have to use this type of encryption, because Oracle Streams do not support TDE in Oracle 10g, and we are replicating encrypted data.

Answer 1

@wateenmooiedag: Sorry didn't see you also mentioned DBMS_ADVANCED_REWRITE. ;)
I made a small testcase to show that DBMS_ADVANCED_REWRITE indeed works as expected:
SQL>  create table table1 (name, ssn) as select 'John Smith' name, to_char(to_clob(dbms_crypto.encrypt(utl_raw.cast_to_raw ('123-45-6789'),1 + 256 + 4096,utl_raw.cast_to_raw('michaels')))) ssn from dual
Table created.
SQL>  select name, ssn from table1
NAME                           SSN                                    
John Smith                     F9B1AEECF8B836BFB4C4B555C3922EE9       
1 row selected.
SQL>  begin
   sys.dbms_advanced_rewrite.declare_rewrite_equivalence
      ('sal_rewrite',
       'select name, ssn from table1',
       'select name, utl_raw.cast_to_varchar2(dbms_crypto.decrypt (ssn, 1 + 256 + 4096, utl_raw.cast_to_raw (''michaels''))) ssn from table1',
       false,
       'general'
end;
PL/SQL procedure successfully completed.
SQL>  alter session set query_rewrite_integrity = trusted
Session altered.
SQL>  select name, ssn from table1
NAME                           SSN                                    
John Smith                     123-45-6789                            
1 row selected.