CA(CA cate Authority) is used to provide certificates (that is, server certificates, which are composed of domain name, company information, serial number and signature information), strengthen the security of information interaction between server and client, and provide related services for certificate operation and maintenance.
Any individual/organization can play the role of CA, but it is difficult to gain the trust of customers. There are many CA vendors that browsers can trust by default, among which TOP5 is Symantec, Comodo, Godaddy, GolbalSign and Digicert.
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Describe CA and certificate in detail.