In a signature creating apparatus, a clock generates a time stamp and in which time can be set only by a computer installed in a certificate authority center. Further, connecting sections connects an apparatus ID for specifying an apparatus and the time stamp and personal identification information for identifying an implementor to a plain-text so as to create data for the signature. A signature creating circuit encrypts the data for the signature using a signature creating key or the like and generates the signature. A connecting section connects the signature to the data for the signature and transmits the data as data after signature.
