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I'm using TeXLive 2021 on 64-bit GNU/Linux (installed in /usr/local, not distro). I currently use pdfLaTeX because I haven't yet needed anything from LuaLaTeX that I can't do in pdfLaTeX, but I'd switch for this.

To accomplish cryptographic digital signatures currently I have to use digsig.sty which isn't from CTAN and appears to be just over six years old now. It extends hyperref but for whatever reason has never been included in hyperref. Perhaps the license?

That can be used to add the form field, but then I have to transfer the file to a PC running Windows to actually sign it – and that means someone else's PC which means my private key is used on a machine I don't administer.

And the signature Adobe Reader DC adds has an Adobe watermark that isn't grayscale, which means print shops always want to charge more to print it color and you have to tell them "No, grayscale is fine."

I know the LaTeX3 team is working on adding tagged PDF features etc. which is long overdue and I welcome but which I also worry will actually break ability to use digsig.sty.

Are there current plans to add digsig.sty functionality to LaTeX along with the tagged PDF support that is being added?

Even more importantly, are there plans to make a CLI tool or whatever that I can use to sign the PDF from Linux directly? (If yes, using a grayscale LaTeX hummingbird as a watermark behind the printed sig would be awesome - but please not color).

Ingmar
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AnymouseProphet
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    with pdflatex I see no reason why the digsig.sty should not work with the new pdfmanagement, with lualatex it will work only if you use also luatex85, with latex it won't work directly as it relies on \pdfmark. And there will be support for signature fields, it is on the todo list, see the documentation of l3pdffield. – Ulrike Fischer Jul 16 '21 at 07:25
  • There's a list of open source tools for digital signatures here including a couple CLI tools that work on linux. I've only ever used okular myself for this on linux. – frabjous Apr 12 '22 at 23:10

1 Answers1

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You can also try eforms.

Here is a sample using both:

\documentclass[12pt]{article}
\usepackage[utf8]{inputenc}
\pdfobjcompresslevel=0 \pdfcompresslevel=0 %create uncompressed pdf for debugging
\usepackage{eforms}
\usepackage{digsig}
\title{Electronic Signature Specimen}
\author{}
\date{June 2021}
\begin{document}
\maketitle
\section{Address}
\TextField[borderwidth=0,multiline,name=toaddress,width=6cm,charsize=12pt,default={E\string\r %modified on 2017-08-08 by
PO Box\string\r
Cape Town\string\r
8000}]{\mbox{}}~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

\section{eforms Signature SignatureFieldLab (preferred)}
\sigField[\Lock{/Action/Exclude/Fields [(toaddress)]}]{SignatureFieldLab}{5cm}{1cm}


\section{digsig Signature lab}
\digsigfield{5cm}{1cm}{lab}
Note that download is required to display the {\tt .pdf} fields.
\end{document}
skvery
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