title: What is null key encryption?
body: <p>In the movie Dark Knight, the Batman builds some ultra powerful sonar monitoring system and encrypts it with &quot;Null Key Encryption&quot;.</p>
  <p>I was reading <a href="https://www.rfc-editor.org/rfc/rfc2410" rel="nofollow noreferrer">RFC 2410</a> but couldn't comprehend it. It says something like this:</p>
  <blockquote>
  <p>However there are cases when only authentication
  and integrity protection is required, and confidentiality is not
  needed or not permitted.</p>
  </blockquote>
  <p>And in the end, the Batman says to another character:</p>
  <blockquote>
  <p>Type in your name when you are finished.</p>
  </blockquote>
  <p>If it's that simple, why encrypt it?</p>