SMARTRA

SMARTRA (SMARt TRansponder Antenna) is a passive challenge-response immobiliser system developed for HMC (Hyundai Motor Company) by Bosch. On the GK platform, version 2 is used, called SMARTRA2.

Not much information can be found online about version 2 of SMARTRA. However, version 3 is backwards compatible and thanks to the FCC, it's protocol specification document is available. SMARTRA3 was assigned the FCC identificator LXP-VIMA01.

Simplified overview of the system

SMARTRA system is composed of three elements, each being vital to it's operation:

• Keyfob transponder
• SMARTRA Control Unit (CU), integrated into the Body Control Module
• Engine Control Unit (ECU/ECM)

In simple terms:

Keyfob stores it's unique identificator ("32 bit identifier"/"Pre Secret Encryption Key") and the 6 byte encryption key.

BCM doesn't store any SMARTRA-related data! BCM is essentially a interface between ECU and the transponder. It doesn't validate transferred data or perform any other checks. Possible confusion on this matter might be related either to the "limp home" function (which is independent from transponder) or the VIN number match check.

BCM does store pincode (for the limp home function) and DPN (see below) but for diagnostic (including new key registration) purposes. Erasing these values shouldn't affect the immobiliser system^[verify].

ECU stores unique identificators of up to 4 keys (transponders) and a 9 byte DPN (Diagnostic PIN Number) of which first 6 bytes are used as the encryption key.

So, in short: Keyfob transponders are paired to ECUs. BCMs are not paired nor contain any transponder data, but they contain the VIN number which has to match with the ECU in order to start the engine.