title: APDU commands, error trying to digitally sign
body: <p>I'm working with smart cards and APDU commands.
  I am trying to digitally sign a hash with the private key inside my card.
  Following some tutorials, I am executing the following script but the last one gives me an error.</p>
  <pre><code>00 20 00 81 06 3x 3x 3x 3x 3x 3x  --VERIFY response: 9000
  00 A4 04 00 XX xx xx xx xx xx xx.....  --SELECT APP response: 9000
  00 22 41 B6 06 80 01 8A 84 01 81  --SECURITY ENVIRONMENT response: 9000
  00 2A 9E 9A XX xx xx xx xx xx xx.....  --SIGN  response: 6a88
  </code></pre>
  <p>In the last command, the expected response would be: <strong>HASH_SIGNED + 9000</strong>. But it is responding: <strong>6a88</strong>.</p>
  <p>Could someone help me, what may be wrong or what am I doing wrong?</p>