Keeping Encrypted Strings Safe with Multiple Encrypts

Question

A system I have been working on for a while requires DPA, and asked a question about keeping the data passcodes safe. I have since them come up with an idea to fix that, which involves having the data decrypt password for the database stored on the database, but have that encrypted with validated users password (which is stored as an MD5 key) after a different type of hashing.

The question is that does encrypting the password multiple times with different keys (at least 20 characters long, with possible extension) make it considerably easier to decrypt without prior knowledge or information on the password?

Answer 1

No, in general a good cipher should have the property that you cannot retrieve data even if you know the plaintext. Having the data encrypted should not have much influence, geven a good cipher and a big enough key space.

Answer 2

First off, MD5 is no longer considered a secure encryption algorithm. See http://www.kb.cert.org/vuls/id/836068 for details.

Secondly, the encryption key for the data should not be stored in the database itself. It should be stored separately. That way there are at least two things that have to be obtained (the database file and the key) to decrypt the data. If the key is stored in the database itself, it probably wouldn't take long to find it once someone has the database file.

Find a separate method for storing the key. It should either be coded into the application or stored in a file that is obfuscated in some way.