Last week was the end of Malika' internship within Papers about signatures that I had the pleasure to mentor. After a post about the first phase of Outreachy, here is the sequel of the story.

Nowadays, people expect to be able to fill and sign PDF documents. We previously worked on features to insert text into documents and signatures needed to be improved.

There is actually some ambiguity when speaking about signatures in PDFs: there are cryptographic signatures that guarantee that a certificate owner approved a document (now denoted by "digital" signatures) and there are also signatures that are just drawings on the document. These latter ones of course do not guarantee any authenticity but are more or less accepted in various situations, depending on the country. Moreover, getting a proper certificate to digitally sign documents may be complicated or costly (with the notable exception of a few countries providing them to their residents such as Spain).

Papers lacked any support for this second category (that I will call "visual" signatures from now on). On the other hand, digital signing was implemented a few releases ago, but it heavily relies on Firefox certificate database ¹ and in particular there is no way to manage personal certificates within Papers.

During her three months internship, Malika implemented a new visual signatures management dialog and the corresponding UI to insert them, including nice details such as image processing to import signature pictures properly. She also contributed to the poppler PDF rendering library to compress signature data.

Then she looked into digital signatures and improved the insertion dialog, letting users choose visual signatures for them as well. If all goes well, all of this should be merged before Papers 51!

Malika also implemented a prototype that allows users to import certificates and also deal with multiple NSS databases. While this needs more testing and code review ² , it should significantly simplify digital signing.

I would like to thank everyone who made this internship possible, and especially everyone who took the time to do calls and advise us during the internship. And of course, thanks to Malika for all the work she put into her internship!