Authentication of a hardware token connected to a computer includes storing, in the hardware token, a computer public key Ck generated in the computer; reading out, from the hardware token to the computer, a user public key Uk, registering the user public key Uk from the computer with a certificate authority, and receiving a certificate issued from the certificate authority with respect to the user public key Uk, and storing the issued certificate for the user public key Uk in the hardware token.