This paper by Ulf T. Mattsson, Chief Technology Officer, Protegrity Corporation, presents a practical implementation of field level encryption in enterprise database systems, based on research & practical experience from years of commercial use of cryptography in db security.
Database encryption
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Eugenia Loli
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To be honest only about 1% of people need something like this. Most of it can be taken care of with simple file permission, as all connection have to connect to your Database’s Serice so not local access file access. It’s only the offsite backups that need encryption. Doing this online just slows down processing. But again most people don’t have clue what there doing.
Considering probably, say, about 80-90% of databases are hosted on a shared hosting environment, the demand might be higher than we think. People ask this sort of thing in MySQL, FB, and PostgreSQL mailing lists from time to time. Although really, the proper way to do this IMO is on the filesystem-level, not the DB-level.
From the December 2003 issue:
http://www.linux-mag.com/2003-12/databases_01.html