title: Office Open XML (OOXML) Specification: Encryption
body: <p>I am trying to understand how encrypted ("password protected") Office 2007 documents are bundled (specifically, Excel documents). I am experimenting with a known, password protected spread sheet.</p>
  
  <p>When I unzip the XLSX file, I encounter three entries:</p>
  
  <ul>
  <li>[6]DataSpaces (Directory)</li>
  <li>EncryptionInfo (File)</li>
  <li>EncryptedPackage (File)</li>
  </ul>
  
  <p>How is the EncryptedPackage file encrypted (which cipher, which key derivation function, etc...)?</p>
  
  <p>I have tried referencing <a href="http://www.ecma-international.org/publications/standards/Ecma-376.htm" rel="nofollow noreferrer">the documentation</a>, but I haven't had much success.</p>