CA (Certificate Authority), also known as e-commerce certification center, is the authority responsible for issuing and managing digital certificates. As a trusted third party in e-commerce transactions, CA is responsible for verifying the legitimacy of public keys in public key systems.

Digital certificate is a series of data that identifies the identity information of network users. In network communication, it is used to identify the identities of both parties, that is, to solve the problem of' who am I' on the network, just like in reality, each of us has to have an ID card or a driver's license to prove our identity or certain qualifications.

Digital certificates are issued by an authoritative and impartial third party organization, namely CA Center. The encryption technology with digital certificate as the core can encrypt and decrypt the information transmitted on the network, digitally sign and verify the signature, thus ensuring the confidentiality and integrity of the information transmitted on the network, the authenticity of the identity of the transaction subject and the undeniable signature information, thus ensuring the security of network applications.