can any one help to secure data in peer to peer model?

As I have two systems and are connected by network cable.While sharing a drive all its data is accessible by another system.Can I make a particular file (word or excel)secure or set security so that another shared computer would not access.If at all required he/she must be prompted for security certificate or password.I will be very helpful if I get appropriate solution.

could put it in a password protected rar file.