Splitting A Table For Security

I'm on a project to build a database for the stores in our area. Things like managers, banks, and partners obviously should be in seperate tables. Most of the information though, seems to belong directly in a table of stores. Basically each record is a store and there will be very many attributes per record (about 30+). Some attributes only relate to certain departments and only someone from that department should see that info. If I broke up the big table into smaller tables it would be the same information but every table would have to have the store number to link it all back together. From a design standpoint this is bad because the store number is redundant.

So my question is, is it a good idea to split up the table for security purposes?

My main concern is security, I can take a hit on performance or storage.