Date update using OBFUSCATION

Question

Hello,
I'm trying to encrypt dates in a DATE type field.  If I perform a select, it encrypts the field:
select dob,dbms_obfuscation_toolkit.md5( input_string => dob ),
from person where person_id = 138;
However, when I try and perform the update, it throws ORA-01858: a non-numeric character was found where a numeric was expected:
update person
  set dob = dbms_obfuscation_toolkit.md5( input_string => dob )
where person_id = 138;
I also tried, but neither of these worked:
     set dob = dbms_obfuscation_toolkit.md5( input_string => to_char(dob,'DD-MON-YY') )
set dob = dbms_obfuscation_toolkit.md5( input_string =>to_date( to_char(dob,'DD-MON-YY'),'DD-MON-YY') )
Thanks,
John

Answer 1

I'm trying to encrypt dates in a DATE type field.
YOU can't do that. Only Oracle can do that.
Anything that you encrypt will have to be stored in a datatype that supports the characters your data might have. That will typically be a BLOB.
See the Advanced Security doc
http://docs.oracle.com/cd/B28359_01/network.111/b28530/asotrans.htm
3 Securing Stored Data Using Transparent Data Encryption
Transparent data encryption enables you to encrypt sensitive data, such as credit card numbers, stored in table columns. Encrypted data is transparently decrypted for a database user who has access to the data. Transparent data encryption helps protect data stored on media in the event that the storage media or data file gets stolen.
3.1.3 How Transparent Data Encryption Works
Transparent data encryption is a key-based access control system. Even if the encrypted data is retrieved, it cannot be understood until authorized decryption occurs, which is automatic for users authorized to access the table.
When a table contains encrypted columns, a single key is used regardless of the number of encrypted columns. This key is called the column encryption key. The column encryption keys for all tables, containing encrypted columns, are encrypted with the database server master encryption key and stored in a dictionary table in the database. No keys are stored in the clear.
As shown in Figure 3-1, the master encryption key is stored in an external security module that is outside the database and accessible only to the security administrator. For this external security module, Oracle uses an Oracle wallet as described in this chapter. Storing the master encryption key in this way prevents its unauthorized use.