I think you may be on to something with ezNcrypt. I hear it is a Transparent Data Encryption solution. It encrypts the data between the database and disc. It's transparent to the application and database so no changes are necessary at all. Just a simple install, then you chose the database tables you want to encrypt. You only encrypt what is necessary, so the performance hit is negligible.
I know people who are using this to encrypt credit card information on application servers for PCI DSS compliance, and heard of someone who is using it to protect intellectual property on a back-end web server.
Key management is the biggest bonus here. It's all automated as part of the solution. Check it out at www.critotech.com .
Security and privacy
Moodle and Encrypted Database
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