I was just conducting research for improvements in security in SQL Server 2008 and came across the below whitepapers which are great references if you are looking at improving security of your SQL Server environment.

 

Engine Separation of Duties for the Application Developer

http://msdn.microsoft.com/en-us/library/cc974525.aspx 

SQL Server 2008 Security Enhancements whitepaper -

http://www.microsoft.com/sqlserver/2008/en/us/wp-sql-2008-security.aspx

  • Database Encryption in SQL Server 2008 Enterprise Edition - in depth treatise on Transparent Database Encryption.
  • Cryptography in SQL Server - Survery of all the cryptography features in SQL Server 2008.