title: Changing key in Mifare 4K Card
body: <p>Can anyone please tell me how to change a key in a Mifare 4K classic card.</p>
  
  <p>What I tried was </p>
  
  <pre><code>&lt;newKeyA&gt; + access bits + &lt;KeyB&gt;
  0xAA 0xAA 0xAA 0xAA 0xAA 0xAA 0X78 0x77 0x88 0x69 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF
  </code></pre>
  
  <p>But the key refuses to change. The default configuration is <code>0xFF 0xFF 0xFF 0xFF 0xFF 0xFF</code>.</p>