Dbms_crypto encrypt date number datatype

Question

I am using oracle 11g. I am very new to dbms_crypto. I went through documentation but have following doubts:
Is it mandatory to convert varchar2(32) to RAW to use dbms_crypto.encrypt?
If I change varchar2(32) to RAW, Can I make it RAW(32) or does it needs to be bigger?
Does the RAW size must be in multiple of 16?
How can I encrypt data of datatype date and number using dbms_crypto?
Thanks a lot for your time to clarify my quries?

Answer 1

spur230 wrote:
Is it mandatory to convert varchar2(32) to RAW to use dbms_crypto.encrypt?It's not mandatory, but it's certainly a good idea. If you store encrypted data in a VARCHAR2 column, that means that it is subject to character set conversion if it's moved from one database to another or sent from a database to a client machine. But if character set conversion happens, your encrypted data is corrupted.
If I change varchar2(32) to RAW, Can I make it RAW(32) or does it needs to be bigger?
Does the RAW size must be in multiple of 16?It would be helpful to specify exactly what algorithm and parameters you intend to use because it may vary. If, for example, we encrypt using AES-256 with Cipher Block Chaining and PKCS#5 compliant padding (which happens to be the example in the DBMS_CRYPTO manual), the output RAW will always be a multiple of 16 and as large or larger than the input RAW.
A VARCHAR2(32) will either allocate 32 characters of storage or 32 bytes of storage depending on your NLS_LENGTH_SEMANTICS parameter. If you're using the default, it will allocate 32 bytes. But 32 bytes in the database character set may require more than 32 bytes of storage once you convert it to a UTF-8 encoded RAW (which, technically, also isn't required but is a good practice) and, thus, the encrypted string might require more than 32 bytes of storage. Your database character set and the actual data you store/ want to be able to store will influence how likely it is that you'll need a larger RAW than your VARCHAR2.
How can I encrypt data of datatype date and number using dbms_crypto?dbms_crypto only operates on RAW data. Just like you convert strings to RAW before encrypting them, you'd need to convert your dates and numbers to RAW. For numbers, you should be able to use UTL_RAW.CAST_FROM_NUMBER. I don't know of a method of casting dates to a RAW other than converting them to a known string representation and then encrypting that (and, of course, doing the reverse when you decrypt the string and convert it back to a date using that same format).
Justin