Patent ID: 8856536

Claim:
A method for authenticating a piece of firmware that is to be downloaded to a vehicle ECU, said method comprising: separating the firmware into a first firmware part and a second firmware part; hashing the first firmware part using a hash function at a first trusted source; encrypting the hash of the first firmware part with a first source private key to create a signature at the first trusted source; hashing the second firmware part using a hash function at the first trusted source; sending the hashed second firmware part to a second trusted source; encrypting the hash of the second firmware part with a second source private key to create a signature at the second trusted source; sending the firmware and the signature of the first firmware part from the first trusted source to a downloading tool; requesting the firmware and the signature of the first firmware part from the downloading tool; requesting the signature of the second firmware part from the second trusted source; sending the signature of the second firmware part to the vehicle from the second trusted source; validating the signature of the first firmware part in the vehicle using a first source public key; validating the signature of the second firmware part in the vehicle using a second source public key; and authenticating the firmware in the ECU if both the first and second firmware parts are valid.