<div class="content"><p>The second type of the <a href="1ef0b4e0-d88e-4b60-bc24-c983bec1e088#gt_9d7b1eb9-8131-4eb3-ad5b-08792b014893" data-linktype="relative-path">Remote Assistance Connection</a>
String packet is a <a href="1ef0b4e0-d88e-4b60-bc24-c983bec1e088#gt_b069acb4-e364-453e-ac83-42d469bb339e" data-linktype="relative-path">Unicode
string</a> in XML format.<a id="Appendix_A_Target_4"></a><a aria-label="Product behavior note 4" href="90b2d2e5-7931-4762-8949-04617e1d9089#Appendix_A_4" data-linktype="relative-path">&lt;4&gt;</a> The details
of this are as follows.</p><dl>
<dd>
<div><pre> &lt;E&gt;
     &lt;A KH=&#34;Protocol-specific Parameter&#34; KH2=&#34;Protocol-specific Parameter&#34; ID=&#34;Authorization String Identifier&#34; /&gt;
     &lt;C&gt;
         &lt;T ID=&#34;Transport ID&#34; SID=&#34;Session ID&#34;&gt;
               &lt;L P=&#34;Port&#34; N=&#34;Server Name&#34; /&gt;   
         &lt;/T&gt;
     &lt;/C&gt;
 &lt;/E&gt; 
  
            
</pre></div>
</dd></dl><p>The novice (server) generates the KH attribute of the Auth
String Node &lt;A&gt; in the Remote Assistance Connection String 2. The expert
(client) validates the value of KH during the RDP connection sequence.</p><p>The KH value is a base64-encoded string of the SHA1 hash of
the <b>PublicKeyBlob</b> field of the server certificate received in
TS_UD_SC_SEC1. The length, in bytes, of the <b>PublicKeyBlob</b> is given by
the <b>wPublicKeyBlobLen</b> field as specified in <a href="../ms-rdpbcgr/5073f4ed-1e93-45e1-b039-6e30c385867c" data-linktype="relative-path">[MS-RDPBCGR]</a>
sections <a href="../ms-rdpbcgr/3e86b68d-3e2e-4433-b486-878875778f4b" data-linktype="relative-path">2.2.1.4.3</a>
and <a href="../ms-rdpbcgr/a37d449a-73ac-4f00-9b9d-56cefc954634" data-linktype="relative-path">2.2.1.4.3.1.1</a>.</p><p>In addition to the KH attribute, the novice (server) SHOULD<a id="Appendix_A_Target_5"></a><a aria-label="Product behavior note 5" href="90b2d2e5-7931-4762-8949-04617e1d9089#Appendix_A_5" data-linktype="relative-path">&lt;5&gt;</a> generate the KH2 attribute of the
Auth String Node &lt;A&gt; in the Remote Assistance Connection String 2. If
this parameter is present in the connection string, the expert (client)
validates the value of KH2 during the RDP connection. If this parameter is
absent in the connection string, the client uses the KH parameter for
validating the server as described in the previous paragraph. The KH2 value is
a composite of the hashing algorithm used and the base64 encoded string of the
PublicKeyBlob field of the server certificate received in TS_UD_SC_SEC1. The
hashing algorithm can be sha256, sha384, or sha512. The hashing algorithm and
base64 encoded string of the hash are separated by a colon (:).</p><p>The Remote Assistance Connection String 2 starts with the
root Node &lt;E&gt;. This root Node contains the following child nodes:</p><ol><li><p><span>    </span>The Auth String
Node &lt;A&gt; has the following attributes.</p>
<table><thead>
  <tr>
   <th>
   <p>Value</p>
   </th>
   <th>
   <p>Meaning</p>
   </th>
  </tr>
 </thead><tbody><tr>
  <td>
  <p>KH</p>
  </td>
  <td>
  <p>Parameters specific to a <a href="1ef0b4e0-d88e-4b60-bc24-c983bec1e088#gt_17c795a6-68bf-46bf-8ea8-467c8df1a0b3" data-linktype="relative-path">Remote Desktop Protocol</a></p>
  </td>
 </tr><tr>
  <td>
  <p>ID</p>
  </td>
  <td>
  <p>Authstring identifier</p>
  </td>
 </tr><tr>
  <td>
  <p>KH2</p>
  </td>
  <td>
  <p>Parameters specific to a Remote Desktop Protocol</p>
  </td>
 </tr></tbody></table>
</li><li><p><span>    </span>The Connector
Node &lt;C&gt; has child nodes that give information on the underlying
Transport used. This Transport Node &lt;T&gt; has the following attributes.</p>
<table><thead>
  <tr>
   <th>
   <p>Value</p>
   </th>
   <th>
   <p>Meaning</p>
   </th>
  </tr>
 </thead><tbody><tr>
  <td>
  <p>ID</p>
  </td>
  <td>
  <p>Transport Identifier</p>
  </td>
 </tr><tr>
  <td>
  <p>SID</p>
  </td>
  <td>
  <p>Session Identifier</p>
  </td>
 </tr></tbody></table>
</li><li><p><span>    </span>The Transport
Node has Listener child Nodes that give information about the Server IP and
port. This Listener node &lt;L&gt; has the following attributes.</p>
<table><thead>
  <tr>
   <th>
   <p>Value</p>
   </th>
   <th>
   <p>Meaning</p>
   </th>
  </tr>
 </thead><tbody><tr>
  <td>
  <p>P</p>
  </td>
  <td>
  <p>Port: The dynamic port on which the Remote Assistance
  connection could happen.</p>
  </td>
 </tr><tr>
  <td>
  <p>N</p>
  </td>
  <td>
  <p>Server Name: The name/IP address of the server, that
  is, the <a href="1ef0b4e0-d88e-4b60-bc24-c983bec1e088#gt_d27bcedc-ae63-4e15-a0cb-9b371f1820dc" data-linktype="relative-path">novice</a>
  computer.</p>
  </td>
 </tr><tr>
  <td>
  <p>U</p>
  </td>
  <td>
  <p>URI: The full URI if websocket listener is enabled.
  The U (URI) is used instead of the P (port) attribute. N (server name)
  attribute is still included.</p>
  </td>
 </tr></tbody></table>
</li></ol><p>The following is an example of Remote Assistance Connection
String 2:</p><dl>
<dd>
<div><pre> &lt;E&gt;
     &lt;A KH=&#34;YiKwWUY8Ioq5NB3wAQHSbs5kwrM=&#34; KH2=&#34;sha256:wKSAkAV3sBfa9WpuRFJcP9q1twJc6wOBuoJ9tsyXwpk=&#34; ID=&#34;8rYm30RBW8/4dAWoUsWbFCF5jno/7jr5t
 NpHQc2goLbw4uuBBJvLsU02YYLlBMg5&#34;/&gt;
     &lt;C&gt;
         &lt;T ID=&#34;1&#34; SID=&#34;1440550163&#34;&gt;
             &lt;L P=&#34;49749&#34; N=&#34;2001:4898:1a:5:79e2:3356:9b22:3470&#34;/&gt;
             &lt;L P=&#34;49751&#34; N=&#34;172.31.250.64&#34;/&gt;
         &lt;/T&gt;
     &lt;/C&gt;
 &lt;/E&gt; 
            
</pre></div>
</dd></dl><p>In the preceding example:</p><ol><li><p><span>    </span>The Auth String
Node &lt;A&gt; has the attribute KH=&#34;YiKwWUY8Ioq5NB3wAQHSbs5kwrM=&#34;, KH2=&#34;sha256:wKSAkAV3sBfa9WpuRFJcP9q1twJc6wOBuoJ9tsyXwpk=&#34;,
and attribute ID =
&#34;8rYm30RBW8/4dAWoUsWbFCF5jno/7jr5tNpHQc2goLbw4uuBBJvLsU02YYLlBMg5&#34;. 
In this example, the KH2 value contains the encoded string
&#34;wKSAkAV3sBfa9WpuRFJcP9q1twJc6wOBuoJ9tsyXwpk=&#34; and the hashing
algorithm used is SHA256.</p>
</li><li><p><span>    </span>The Connector
Node &lt;C&gt; has one Transport child Node &lt;T&gt; with the following
attributes:</p>
<p>ID = &#34;1&#34;</p>
<p>Session ID - SID =
&#34;1440550163&#34;</p>
</li><li><p><span>    </span>The Transport
Node has two Listener child Nodes &lt;L&gt; with the following server and port information
attributes:</p>
<p>Port - P =
&#34;49749&#34;</p>
<p>Server Name - N =
&#34;2001:4898:1a:5:79e2:3356:9b22:3470&#34;, and</p>
<p>Port - P =
&#34;49751&#34;</p>
<p>Server Name - N =
&#34;172.31.250.64&#34;.</p>
</li></ol></div>