简述PKI服务的概念。
简述PKI服务的概念。
相关考题：
Which of the following is NOT related to a Public key infrastructure (PKI)?以下哪个概念与公钥基础设施（PKI）无关？（）A、A X.509 certificate（X.509证书）B、A Ticket Granting Service（票据授予服务）C、A Registration authority（注册机构）D、A Certificate authority（证书机构）
单选题Which of the following is NOT related to a Public key infrastructure (PKI)?以下哪个概念与公钥基础设施（PKI）无关？（）AA X.509 certificate（X.509证书）BA Ticket Granting Service（票据授予服务）CA Registration authority（注册机构）DA Certificate authority（证书机构）
问答题简述PKI的定义和服务。