Before diving into algorithms and key management, one should ask What to you want to protect against? Some challenges are

• Direct access to file and log file viewing/tampering.
• System user privilege abuse.
• Stolen or lost media.

At work I face some of these requirements and I find it hard to come up with a satisfying solution.

There are plenty of articles on database encryption, e.g. Encrypting Data Values in DB2 Universal Database (ibm.com/developerworks) which describes using Column level encryption in the DB2 database. While an interesting read, the article does not touch on key management. The question of where do we store the keys remain unanswered.

I recommend reading the Payment Card Industry Data Security Standard Specification (pcisecuritystandards.org). The PCI DSS Specification outlines a series of principles on how financial institutions are to protect financial data (credit card details etc). Again, there is no definitive implementation, but some of the ideas behind it are interesting (from section 3):

• Keep cardholder data storage to a minimum.
• Do not store sensitive authentication data subsequent to authorization (even if encrypted).
• Render [cardnumber], at minimum, unreadable anywhere it is stored (including data on portable digital media, backup media, in logs, and data received from or stored by wireless networks).

I find the idea of not storing sensitive data unless it's absolutely necessary particularly interesting.

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