Different GM modules (ECUs) use different algorithms. Knowing the algorithm ID is crucial for calculation. Often use the B216cap B 2 sub 16 algorithm. E78 Modules: Frequently utilize the 461646 sub 16 algorithm.
2010 Chevrolet Equinox (BCM controlled immobilizer) Task: Add a new transponder key (PK3+) gm 5 byte seed key
Before focusing on GM’s specific implementation, we must understand the concept of a Seed Key (S/K) system. It is a challenge-response authentication protocol used on the Controller Area Network (CAN) bus or K-Line (ISO 9141-2). Different GM modules (ECUs) use different algorithms
This is a popular topic in the automotive security and tuning community because it governs access to protected diagnostic services (like reflashing the ECU) via the protocol. E78 Modules: Frequently utilize the 461646 sub 16 algorithm
Unlike older systems where a single formula might cover many cars, the 5-byte system is heavily customized. Each ECU vendor (e.g., Bosch, Continental) creates their own security table and generates a dynamic DLL file. This ensures that a single cracked algorithm cannot be used to unlock all GM vehicles. 3. Implementation and Calculation (5-Byte Algorithm)
The first 5 bytes of the AES output become the final key (MAC). 5. Challenges in Independent Diagnostics
def gm_5byte_key(seed_bytes): # seed_bytes: list/tuple of 5 ints (0-255) # Returns 5-byte key for common E37/E39 variant A = 0x4D B = 0x6A key = [0]*5 for i in range(5): temp = (seed_bytes[i] * A + B) & 0xFF key[i] = temp ^ seed_bytes[(i+1)%5] return bytes(key)