Well you know have kind of shifted gears. At first you wanted to protect the data. That is a good idea with any sensitive information. It sounds like you have encrypted those columns now. That means that data is protected at rest.

Now however you want to disallow selecting certain columns to certain users. This is a different animal. The article here does a good of explaining how you can implement this with column level permissions.

http://www.mssqltips.com/sqlservertip/2124/filtering-sql-server-columns-using-column-level-permissions/[/url]

Another way it to use views. Here is a decent article that explains a way to do that.

http://www.mssqltips.com/sqlservertip/2125/filtering-columns-in-sql-server-using-views/[/url]