Certification will be performed without the use of any external
certification organizations in an organization such as an enterprise. A
server and a plurality of clients are connected via a network to thereby
constitute a certification system for the entire enterprise. A public
secondary memory in the server holds a server name, a certificate list, a
temporary registrant list and the like. The certificate list includes
individual and group certificates, and the certificate includes specifying
information on a certification target, a public key and signature by an
responsible person of a group, to which the certification target belongs.
The group responsible person signs the public key of the group member and
specifying information by using the information on a registrant list to
generate a certificate.
