Digital Signatures in OOo
You can obtain a certificate from a certification authority to sign your documents.
By signing an OOo document with your digital signature, you can ensure that the person who gets your document can verify the document is still the same version that you saved.
The receiver of your document will see an icon in the Status Bar which confirms “yes, the document is the same as the saved version”.
If you or someone else change the document, the icon will look broken and thus give the information “this document was signed, but now it has been changed from the original version”.
In the OOo Help, you can find a page which describes how to obtain a certificate, and how to digitally sign your OOo documents.
Press F1 to open Help.
On the Index tab page, enter “digital signature” and double-click the entry.
Another introduction to digital signatures in OOo was published October 12th 2006, by Dmitri Popov on LinuxToday: http://www.linuxtoday.com/security/2006101201426OSHL
Click the Complete Story link to read the fine introduction by Dmitri, and do not hesitate to visit his OOo page at http://www.nothickmanuals.info/doku.php