by the asymmetric algorithms a private key needs to be stored in the information security device beforehand the information security device digitally signs the public key generated by it using the private key stored beforehand as the authentication information the private key stored beforehand can neither be exported nor be used for other purposes but can only be used to generate the authentication information for the public key generated by the information security device if the authentication information is generated by symmetric algorithms or hamc a key needs to be shared between the ca and the information security device the information security device uses the shared key to calculate for the public key generated by it a message authentication code as the authentication information of course the shared key cannot be used for other use either as attackers cannot forge the authentication information generated by the information security device they cannot replace the public key and the self signature in the request file of a certificate and cannot defraud the ca without being detected after a public private key pair is generated outside the information security device in order to prevent the public key from being replaced by trojan program which imports forged public key into the information security device and then exports that make the information security device use the public key generated by the trojan program to generate authentication information the following two means can be used to solve this problem a first means is that the public key is.