什么是 CA

https://www.digicert.com/

https://cn.globalsign.com/

Certificate Authority

为网站颁发证书的权威机构

The more your customers trust you, the more they buy from you. DigiCert provides the best identity assurance in the industry, so visitors to your website will know who they are doing business with. Smart companies all over the world use DigiCert's EV SSL certificate, secure site seal, and branding to help build trust.