Klaus Knopper answers your Linux questions

Signing Documents in Open/LibreOffice

Can I use SSL encryption and signature for OpenOffice/LibreOffice, too?

Although Open/LibreOffice does not support file encryption yet, it does support digital signatures by adding a signed checksum to its internal ZIP-like document archive structure. When the document changes, the checksum is different, and the signature shown is no longer valid for the document. Therefore, if changes are made to the document, even the original author must sign the document again to verify its authenticity.

Because the signature part of Open/LibreOffice is shared with the Mozilla encryption library, all of your certificates and private key are present and can be used immediately if you previously imported your private/public SSL keypair into Firefox, and you can start signing documents right away. For signature verification, recipients of documents need the corresponding public key (public.pem) imported into Firefox so that Open/LibreOffice can verify the signature.

To sign a document or verify its signature, select File | Digital Signatures. You can add a signature to the document by signing with your SSL secret key, taken from the Firefox database. A document can have multiple signatures.


  1. TrueCrypt: http://www.truecrypt.org/
  2. 7-Zip archiver: http://7-zip.org

The Author

Klaus Knopper is the creator of Knoppix and co-founder of LinuxTag expo. He currently works as a teacher, programmer, and consultant. If you have a configuration problem, or if you just want to learn more about how Linux works, send your questions to: klaus@linux-magazine.com

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