Quote Originally Posted by Cnfhbr View Post
It's not like that.
GMA file of course contains unlock codes, the validity of which is confirmed by a digital signature in the file. The main thing in this file is a valid signature.
Shure it's some kind of signature. Anyway that's my experience. Some time ago my vendor said that starting from the next map version current "license" is no more valid (as the map's FID value has increased) so each customer have to "renew" it individually according to the procedure. So I'd sent them ID of my unit and the vendor did responded with the .gma file generated. Actually, in order to get the map working, all I have to do is to place that .gma file next to gmapsupp.img in the ext. storage media. There are no other related files like .unl, etc. The .gma file missing results in auth error so the map is indeed protected. And that .gma file is the sole mean to unlock the map. I've no idea if that's right or wrong but it in my case it works in that manner.

Thanks for the quote from the official Overview. Could you provide a direct link to the related Garmin page?