truct: Credential</h3>
<table class="table-bordered table-striped table-condensed"><thead><th>Key</th><th>Field</th><th>Type</th><th>Description</th><th>Requiredness</th><th>Default value</th></thead>
<tr><td>1</td><td>type</td><td><code><a href="Authentication.html#Enum_UserType">UserType</a></code></td><td>用户登录类型
</td><td>required</td><td></td></tr>
<tr><td>2</td><td>secretKeyId</td><td><code>string</code></td><td>用于服务端查询SecretKey的键值:
1) userId: 对应User Secret
2) appId: 