Patent ID: 8261083

Claim:
An information distribution system, comprising: an information distribution center for distributing map information; and a navigation apparatus, wherein: the information distribution center further comprises: a key generating device that generates a plurality of sets of one public key and one secret key and setting priorities for the plurality of sets of one public key and one secret key; a secret key storage device that stores the plurality of secret keys with the priorities; an electronic signature generating device that generates an electronic signature by using one secret key whose priority is stored as being top in the secret key storage device; a distributing device that distributes the map information with the electronic signature; an input device that accepts an input of a secret key change request for a secret key whose priority is top; and a change request determining device that determines whether the secret key change request for a secret key whose priority is top has been input on the input device, wherein if the change request determining device determines that the secret key change request for the secret key whose priority is top has been input on the input device, the key generating device invalidates the secret key whose priority is top; and the navigation apparatus further comprises: a public key storage device that stores the plurality of public keys with the priorities issued by the information distribution center; an electronic signature extracting device that extracts the electronic signature set for the map information which is distributed from the information distribution center; a verification control device that performs control to verify the electronic signature by using the plurality of the public keys with the priorities in order of the priorities; and a determining device that determines that the map information is valid information distributed from the information distribution center, provided that the electronic signature passes verification, wherein the verification control device performs control to, provided that there is a public key which does not pass the verification before the electronic signature passes the verification, set the public key which does not pass the verification as invalid.