That makes it considerably easier because you can use .Net inside the database. You'll have to experiment to find the best way, but the possible options are a user defined datatype or some sort of trigger. This article may help with the encryption itself
http://msdn2.microsoft.com/en-us/library/aa302352.aspx>2005
Craig Berntson
MCSD, Microsoft .Net MVP, Grape City Community Influencer