Patent ID: 7551986

Claim:
A program distribution system comprising: a program distribution device that distributes a program conducting an access to a given ECU of a plurality of ECUs provided in a vehicle, and an identifier that defines an access right to the given ECU; and a gateway device that is provided in the vehicle and receives the distributed program and the distributed identifier, wherein the program distribution device generates a first digest from the program and the identifier using a converting algorism, generates an electronic signature by encrypting the first digest using a secret key, wherein the secret key is pared with a public key in a public-key cryptography, and distributes the generated electronic signature, the program, the identifier, and the public key, and wherein the gateway device determines an electronic signature validity by comparing a second digest, which is generated from the received program and the received identifier using the converting algorism, with data obtained by decrypting the received electronic signature using the public key, and wherein, when the electronic signature validity is affirmatively determined, the gateway device sets, to the received program, an access right to the given ECU, and prohibits the received program from conducting an access to other ECUs excluding the given ECU, based on the received identifier.