Where is ignition key authentication done?

[JimbobUK]

I seem to remember hearing once that the key inserted into the ignition is authenticated (via transponder) with the car ECU...

Is this true, and how does re-flashing the ECU affect this?

Where is the key transponder actually authenticated?

Where is the pincode (entered in to the keypad next to the steering column) authenticated? Is this in the ECU, or in the Sigma alarm / immobiliser box that is added for some regional markets?

Thanks,
James

[crispyduck]

I seem to remember hearing once that the key inserted into the ignition is authenticated (via transponder) with the car ECU...

Is this true, and how does re-flashing the ECU affect this?

Where is the key transponder actually authenticated?

Where is the pincode (entered in to the keypad next to the steering column) authenticated? Is this in the ECU, or in the Sigma alarm / immobiliser box that is added for some regional markets?

Thanks,
James

I'm no expert however have an opinion on this. The imobilser (CAT2) and alarm (CAT1) are separate. If you parallel import a car you get the CAT2 imobiliser which all works of the transponder in the car key.

You can then add the sigma bolt-on to the imobiliser which extends it to CAT1. From memory the keypad only provides an override for the alarm and is authenticated in this bolt-on - the alarm, not the ECU.

Others on here should know more than me on this subject. I'd be interested to know how the ECU authenticates the transponder, although I expect this to be complicated involving random keys etc.
-Steve.

[JimbobUK]

Thanks crispy,

This is kindof what I was expecting about the Sigma add-on unit.

I would like to know more about the transponder... When we re-flash the ECU, do we need to re-authenticate our keys?

James

[crispyduck]

... I would like to know more about the transponder... When we re-flash the ECU, do we need to re-authenticate our keys?

Well I didn't. I've done about four reflashes so far. All reflashes were based on my original ECU image and changed the maps from this. Not sure if the answer would be different if I reflashed an ECU image from another car or even different model year.

With that said I would like to assume that the key is embedded in to the ECU hardware, not in the software. This would be analogous to say the unique MAC address of a network card on PC which people use as the seed value for software licence protection. Perhaps the ECU is doing something similar by reading a unigue serial number off the hardware then with simple public/private key encryption this would tie a transponder key to a single ECU.

Anyone, one tell us for sure…
-Steve.

[JimbobUK]

I seem to remember that one can authenticate a number of key transponders with a particular car (add / delete)... So there must be some area of memory associated with this... Maybe it is 68HC16 memory, or it could be something else on the ECU board, or even external to the main ECU.

If it is 68HC16 memory then I need to find out how to authenticate my keys after a complete reflash!

[Xmicho]

I can confirm that reflashing a map from another car will not affect the immobiliser. Tried it and the key still worked. Swapping the ecu with one from another car will immobilise the car. Tried that too.

[richh]

Not sure whether this remains the case on the latest cars, but on the late GC/GF8's the immobiliser is a self-contained unit located under the dash area, with an antenna lead plugged into the steering lock assembly which reads the transponder.

As such, it's unsurprising that reflashing the ECU on these cars doesn't require the keys to be reprogrammed.

The keypad is, as has already been mentioned, part of the Sigma M30 alarm system which is fitted once cars have arrived in the UK, and nothing to do with the factory fit electronics.