Patent ID: 8909931

Claim:
A server authentication system in which clients authenticate a server, wherein the server comprises: an address key allocation unit that generates an identifier to identify each of the clients by a combination of addresses on a plurality of address spaces, and allocates, in a one-to-one manner, address keys to the respective addresses configuring the generated identifier; and a message authentication code generation unit that generates message authentication codes corresponding to a message by using the address keys allocated by the address key allocation unit, the message authentication codes generated for each of the clients being in a one-to-one relationship to the address keys allocated for each of the clients, and each of the clients comprises a server authentication unit that authenticates the server based on the message authentication codes generated by the message authentication code generation unit, wherein a part of the addresses configuring the identifier generated for each of the clients configures a portion of an identifier generated for at least one different client among the clients, the address keys allocated for each of the clients are not correlated with each other and thus a part of the address keys allocated for each of the clients is in common with a part of the address keys allocated for at least one different client among the clients, so that a number of the allocated address keys is smaller than a number of the clients, and wherein a part of the message authentication codes generated for each of the clients is in common with a part of the message authentication codes generated for at least one different client among the clients, because the part of the address keys allocated for each of the clients is in common with the part of address keys allocated for at least one different client among the clients.