Digital certificate ensures the integrity and security of information and data by encrypting or decrypting the information and data of network users in computer network communication. When a user applies for a certificate, there will be two different certificates, one for the work computer and the other for verifying the interaction of user information. Users can immediately apply for, open and use digital certificates, and can choose the corresponding digital certificate protection technology according to users' needs. Users don't need to master the encryption technology or principle, and can directly carry out security protection through digital certificates.