I'd label it more as "heterogenous security." If everyone modded their own car, a thief is forced to develop novel attacks for each car. Immobilisers have two

I'd label it more as "heterogenous security." If everyone modded their own car, a thief is forced to develop novel attacks for each car. Immobilisers have two major issues. The first is code weakness. Many of the early ones used static keys. In '98 when Germany mandated them for new cars, BMW and others switched to using the odometer reading as a shared secret. Newer ones often use weak 40-bit keys. The second issue is that most immobilizers simply cut the ignition circuit and the fuel pump circuit. If you know where the relays are on a model of car you can short circuit them.