用户认证层提供客户端身份验证以及多种验证方法。

A user authentication layer provides authentication for clients as well as several authentication methods.

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用户认证协议：该协议从服务器到客户端进行身份验证，且通过传输层运行。

User Authentication protocol: This protocol authenticates the client to the server and runs over the transport layer.

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但是，在开始之前，请注意在上一篇文章(“身份验证和授权”)中，我加入的认证使UI中出现一个细小的bug。

But before you get started, the authentication I added in the preceding article (" authentication and authorization ") introduced a subtle bug in the UI.

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