Not sure what you mean about "fobs with different identities".
IIRC Keeloq fob ICs (HCS301 etc) have a crypt secrect code (encyption key derived from a secret manufacturer code*) and the fob 'serial' number.
* All of your system components must use a key derived from the manufacturer secret code.
This is what allows them to charge an-arm-and-a-leg for a new button remote.
With the code at my link above you become the manufacturer, with your own secret code.
Well, yes, I know that, but...
Swake mentioned difficulty finding fobs with different identities. For ones using Keeloq, the identity would be the serial number, and I would have thought that it would be difficult to find fobs with the
same serial number (except for the far-out possibility that I mentioned of a maker getting very lazy).
Nor do I know why fobs with the same identity would be useful, as that would surely make it difficult to erase one of them only from the receiver (besides the fact that using two fobs with the same identity on the same receiver could be problematic).
Of course, if you make your own receiver, then you are free to come up with some way to erase only one of the fobs. You don't have to make your own fobs, but you'd have to know, or be able to derive, the fob keys, or else reprogram the fobs (if possible) with your own keys. Well, for Keeloq classic you could totally cheat in the receiver, and just ignore the encrypted portion of the transmission (all you need to react to a button press is contained in the non-encrypted part). That would, of course, totally defeat the purpose of having a rolling/hopping code, but, would you believe it, I have found "universal" receivers that do exactly that.