CYPHERPUNKS TO THE RESCUE

[Joseph Block]

Re:
> P.S. Better yet: There is no need of Public key technology. It suffices for
> the car unit to send DES(k, n) on the nth transmission. k is a constant
> secret key shared between car unit and garage unit. Garage unit decodes and
> verifies that n is greater than it has seen before.

The only problem with this is that you are limited to one remote per base
station.

jpb