① Information authentication: to confirm the integrity of information, that is, the original message sent by the message sender has not been tampered with or forged by a third party during the message transmission.
② Protocol authentication: to confirm the authenticity of the subject, which is suitable for the first authentication of the system.
③ Digital signature: authenticate the source of data, verify whether the data has changed, and prevent the communication parties from cheating each other.
④ Public key infrastructure PKI: an information system that provides general security services for information security. KPI mainly includes CA, RA, certificate base, certificate management system, key management and other components.