Tips to create an extension for digital signature

[Alfredo Parisi]

Hi  all,
first of all thank to all of you for the wonderful list's job.
I'm a member of LibreUmbria project from Perugia, Italy. LibreUmbria's 
scope is to migrate Local and Regional Administration on Umbria Region 
to LibreOffice.
Italian PA needs digital signature in every official documents so we 
developed a digital signature macro in LO 4.0 and we'd like to trasform 
it in  extension, so the users can install it and try.
The extension should be more helpful for Italian Public Administrations 
and users and easier manageable.

Is there anybody who can help with tips, guide or links?

Thank you