[enuddleyarbl]

As an experiment to see if there's any downside to switching to epub3, I went to Tools > Upgrade Book Internals in the Editor and converted an epub2 book over to epub3. The only odd thing I see is that the conversion process added an encryption.xml file under Miscellaneous. It looks like it's for previously hidden fonts (see below). Normally, when I mess with a book's html, I get rid of all the embedded fonts. Since these appeared in that file (and appear encrypted (I guess?)), what happens if I delete the file? Should I delete it?

EDIT: EPUBCheck is throwing warnings that all the .html files showing in the editor should be .xhtml files. Should the Editor's "Upgrade Book Internals" process have renamed them? Should I rename them?

<?xml version='1.0' encoding='utf-8'?>
<encryption xmlns="urn:oasis:names:tc:opendocument:xmlns:container" xmlns:enc="http://www.w3.org/2001/04/xmlenc#" xmlns:deenc="http://ns.adobe.com/digitaleditions/enc">
  <enc:EncryptedData>
    <enc:EncryptionMethod Algorithm="http://ns.adobe.com/pdf/enc#RC"/>
    <enc:CipherData>
      <enc:CipherReference URI="fonts/00002.ttf"/>
    </enc:CipherData>
  </enc:EncryptedData>
  <enc:EncryptedData>
    <enc:EncryptionMethod Algorithm="http://ns.adobe.com/pdf/enc#RC"/>
    <enc:CipherData>
      <enc:CipherReference URI="fonts/00003.ttf"/>
    </enc:CipherData>
  </enc:EncryptedData>
  <enc:EncryptedData>
    <enc:EncryptionMethod Algorithm="http://ns.adobe.com/pdf/enc#RC"/>
    <enc:CipherData>
      <enc:CipherReference URI="fonts/00004.ttf"/>
    </enc:CipherData>
  </enc:EncryptedData>
  <enc:EncryptedData>
    <enc:EncryptionMethod Algorithm="http://ns.adobe.com/pdf/enc#RC"/>
    <enc:CipherData>
      <enc:CipherReference URI="fonts/00005.ttf"/>
    </enc:CipherData>
  </enc:EncryptedData>
</encryption>