I was
wondering about using a "donor" PCB from a fob, too. In my other life I work on securing systems, and it sounds like Porsche is using
asymmetric encryption (or some variant thereof) with the fobs to lock/unlock the car. In this case it sounds like fob probably transmits a public key (over the air and easily intercepted/read). The tag accompanying it is the matching private key; it gets entered into the immobilizer control unit when it is programmed to recognize the fob. (The tag gets thrown away and the key is only available in the immobilizer control unit - thus, "private.")
It might be possible to identify a private key (what would be on the tag with a new fob) using a cryptographic attack, but a successful attack would be determined in large part by the algorithm Porsche used to generate the key pairs. If that's even what they did....
Hybrid Mode
