US Patent 7779250 Method for applying certificate

The invention is directed to a method for applying a certificate suitable for a portable telephone belonging to a user, wherein the portable telephone comprises a telephone number. The method comprises steps of generating a user key pair in the portable telephone, wherein the key pair comprises a user public key information and then transmitting an applying packet from the portable telephone to a certificate authority through a switching center by using a short message service, wherein the applying packet comprises at least the user public key information. The user is verified according to the telephone number received by the certificate authority from the switching center. A certificate packet is generated by the certificate authority, wherein the certificate packet comprises at least a serial number and a certificate authority signature. The certificate packet is transmitted to the portable telephone according to the telephone number by using the short message service.