title: Make MIFARE Classic 1K read only through an Android app
body: <p>I would like to make MIFARE Classic 1k cards read only after writing some initial data to them. I guess I need to change keys A and B to something custom after writing data to the new card. But how do I do that? These keys are located in the same block as the access bits, so I can't use MifareClassic method for writing a complete block:</p>
  
  <pre><code>public void writeBlock(int blockIndex, byte[] data) throws IOException
  </code></pre>
  
  <p>because it will also rewrite the access bits.</p>