I have had some success working with a product called 'xp_Crypt'.

If you would like to look into this product, check out 'www.activecrypt.com'. 

I had a need to encrypt account numbers that where to be accessed from an in-store kiosk.  I found this product very easy to work with and understand.  The nicest thing about it was the Free Ware version worked just fine for my requirements.  However there is a expanded version that you can by that gives you better performance and capabilities.

Dave