title: Open/Crack zip and disover his password
body: <p>In a lesson of Computer Security our teacher showed us how to find out the password of a zip.</p>
  
  <p>I tried his steps at home but now I'm stuck:</p>
  
  <ol>
  <li>Created 2 zip with same file: <code>plain_zip.zip</code> without password and <code>encrypted_zip.zip</code> with a 4 characters psw: <code>1234</code></li>
  <li>Create another zip with another file: <code>plain_zip_2.zip</code> and <code>encrypted_zip_2.zip</code>.</li>
  <li>Show through terminal his header (I don't remember the command line) and see that both: <code>plain_*.zip</code> and <code>encrypted_*.zip</code> has similar lines</li>
  <li>Through a <code>XOR operation</code> between encrypted and plain zip find out the password. (He told us that's possible only if the password is 4 characters)</li>
  </ol>
  
  <p>Now someone can tell me if these steps are correct? And moreover, how can see the header of a file? (I tried with: <code>head -n 1 plain_zip.zip</code> without success)</p>