SQL Server 2005/2008 - Cryptography in SQL Server

Summary: Although cryptography provides SQL Server with powerful tools for encryption and verification, these are often not well understood. This can lead to poor or incomplete implementations. This white paper presents an overview of cryptographic functionality and discusses how this applies to authentication, signed procedures, permissions, and encryption. Because the target audience is the database professional and not necessarily security experts, the focus is on practical ways to use cryptography in SQL Server.

http://msdn.microsoft.com/en-us/library/cc837966.aspx