AP and SM security

I am not familar at all with the AP’s and SM’s have only deployed BH’s. I have one situation where we will be using an AP and 2SM’s to connect a pair of offices. What do I need to do to prevent other SM’s from being able to access our AP? Authentication keys?

BAM would be the most straight forward answer, although several on the forum are accomplishing this with “roll yourown” methods.