title: What is the difference between the x.509 V3 extensions Basic Constraints and Key Usage to create a CA certificate?
body: <p>These two actions seem to do the same:</p>
  
  <ul>
  <li>using the <strong>Basic Constraints</strong> extension in a X.509 Certificate to signify that it is a CA certificate and</li>
  <li>using the <strong>Key Usage</strong> extension e.g. to signify that the public key can be used for certificate signining.</li>
  </ul>
  
  <p>What is the difference between these extensions?<br>
  Do they serve same purpose or complement each other?</p>