REQUIRED - if the SSL client does not send a certificate, authentication fails.

REQUIRED——如果SSL客户端不发送证书，验证失败。

youdao

Notice that in the previous scenario involving client authentication, the client presents a certificate that is validated by the server against the set of trusted certificates.

请注意，在前面涉及客户端身份验证的场景中，客户端提供一个证书，然后服务器针对受信任的证书集对其进行检验。

youdao

You are using client certificate authentication to the Web server as discussed in the previous section.

像前一小节讨论的一样，使用客户机证书向Web服务器验证身份。

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