Patent ID: 8392716

Claim:
A digital signature issuance method for issuing, in a digital signature issuance apparatus, a digital signature to a second apparatus which communicates with a first apparatus, comprising the steps of: receiving a parameter from the first apparatus; computing data, based on the parameter received from the first apparatus, for use by the second apparatus to share secret data for encryption with the first apparatus; issuing a result of the computation to the second apparatus; receiving, from the second apparatus, data which is calculated by the second apparatus based on the shared secret data; generating a digital signature, using a private key, for both an address of the second apparatus and the data which is calculated by the second apparatus based on the shared secret data, wherein the digital signature is generated using the private key so as to be usable by the first apparatus for authentication based on the shared secret data and the address of the second apparatus used to share the secret data; and issuing to the second apparatus, the digital signature generated in the generating step and a public key certificate, wherein the public key certificate includes an address of the digital signature issuance apparatus, a public-key corresponding to the private key used for generating the digital signature, and information defining that the digital signature issuance apparatus generates a digital signature.