A method for authenticating a communication partner using an electronic certificate containing personal information, the method comprising the steps of: in a client apparatus, receiving a request for an electronic certificate from a server apparatus; in response to the reception of the request, reading a client certificate from a storage device of the client apparatus; and determining if the client certificate contains personal information, wherein the client certificate is sent unencrypted to the server apparatus if the client certificate does not contain personal information, and wherein if the client certificate contains personal information, the client certificate is encrypted using server public key of the server apparatus as stored in the storage device of the client apparatus; a temporary electronic certificate is created by setting determination information in a first field of an electronic certificate and the encrypted client certificate in a second field of the electronic certificate, of which format is supported by the server apparatus, the determination information indicating that the electronic certificate is a temporary electronic certificate; and the temporary electronic certificate is sent to the server apparatus, wherein the method further comprises the steps of: in the server apparatus, receiving an electronic certificate; retrieving determination information from a first field of the received electronic certificate; determining whether or not the determination information indicates that the received electronic certificate is a temporary electronic certificate; if it is determined that the received electronic certificate is a temporary electronic certificate, retrieving the encrypted client certificate from the second field of the temporary electronic certificate; decrypting the retrieved client certificate using a server private key corresponding to the server public key; and authenticating the client apparatus using the decrypted client certificate, and wherein the method further comprises the step of authenticating the client apparatus using the received electronic certificate, if it is determined in the server apparatus that the received electronic certificate is not a temporary electronic certificate. in a client apparatus, receiving a request for an electronic certificate from a server apparatus; in response to the reception of the request, reading a client certificate from a storage device of the client apparatus; and determining if the client certificate contains personal information, wherein the client certificate is sent unencrypted to the server apparatus if the client certificate does not contain personal information, and wherein if the client certificate contains personal information, the client certificate is encrypted using server public key of the server apparatus as stored in the storage device of the client apparatus; a temporary electronic certificate is created by setting determination information in a first field of an electronic certificate and the encrypted client certificate in a second field of the electronic certificate, of which format is supported by the server apparatus, the determination information indicating that the electronic certificate is a temporary electronic certificate; and the temporary electronic certificate is sent to the server apparatus, wherein the method further comprises the steps of: in the server apparatus, receiving an electronic certificate; retrieving determination information from a first field of the received electronic certificate; determining whether or not the determination information indicates that the received electronic certificate is a temporary electronic certificate; if it is determined that the received electronic certificate is a temporary electronic certificate, retrieving the encrypted client certificate from the second field of the temporary electronic certificate; decrypting the retrieved client certificate using a server private key corresponding to the server public key; and authenticating the client apparatus using the decrypted client certificate, and wherein the method further comprises the step of authenticating the client apparatus using the received electronic certificate, if it is determined in the server apparatus that the received electronic certificate is not a temporary electronic certificate. in the server apparatus, receiving an electronic certificate; retrieving determination information from a first field of the received electronic certificate; determining whether or not the determination information indicates that the received electronic certificate is a temporary electronic certificate; if it is determined that the received electronic certificate is a temporary electronic certificate, retrieving the encrypted client certificate from the second field of the temporary electronic certificate; decrypting the retrieved client certificate using a server private key corresponding to the server public key; and authenticating the client apparatus using the decrypted client certificate, and wherein the method further comprises the step of authenticating the client apparatus using the received electronic certificate, if it is determined in the server apparatus that the received electronic certificate is not a temporary electronic certificate.