netsim/levels/01 Basics/level06.html

<p>Routers and modems can read the contents of packets they relay. To protect confidentiality on the Internet, we should thus use <strong>encryption</strong> 
 to make our messages look like nonsense to outsiders. In this level, we introduce a simple encryption protocol that allows two parties to communicate 
 privately.</p>

<p>This "encryption" protocol involves packets with three different types of messages (specified at the application layer):</p>
<ul>
  <li><strong>keyrequest</strong> is used to specify one's own key and request the other party's key.</li>
  <li><strong>keyresponse</strong> is a response to a <strong>keyrequest</strong> and includes only one's own key.</li>
  <li>After these first two steps have occurred, the two parties can exchange <strong>message</strong> packets, encrypted with the recipient's key.</li>
</ul>

<p>To pass this level, send an <strong>encrypted message</strong> from Alice's computer to Bob's computer. You must first have Alice and Bob exchange keys. 
Alice's encryption key is <strong>12345</strong>.</p>
 
<p><em><strong>Hint:</strong> there is an example of how the encryption protocol works at the top of the field.  Use the <span class="button">pause</span> 
button to see what the values of the packet headers are in the protocol.</em></p>

 <h3>Level Objectives</h3>

<ul>
  <li>have Alice and Bob exchange encryption keys</li>
  <li>send an encrypted message from Alice to Bob</li>
</ul>