SecureJoin protocols are designed to counter MITM-attacks on Autocrypt E-Mail encryption and are implemented and released by the Delta Chat e-mail messenger.

This description is derived and refined from the the first two sections of CounterMitm which were written by reseachers of NEXTLEAP, a 2016-2018 project on privacy and decentralized messaging, funded through the EU Horizon 2020 programme.

There are two public web pages:

• https://securejoin.readthedocs.io/en/latest/

• https://securejoin.delta.chat

If you want to do Pull Requests please note that we are using Semantic Linefeeds. It means that the source code of this document should be broken down to a "one-line-per-phrase" format, as to make reviewing diffs easier.

While this Readme uses Markdown syntax, the actual document uses the richer RestructuredText format and in particular the "Sphinx Document Generators". You can probably get around by just mimicking the syntax and "tricks" of the existing text. You may also look at this reStructuredText Primer for some basic editing advise.

For the images we use inkscape to convert them from svg to pdf.

In order to create the documents you will need make, sphinx and inkscape installed on your system. On a Ubuntu/Debian based system you can achieve this with something like:

sudo apt install python3-sphinx inkscape python3-sphinxcontrib.svg2pdfconverter

From there on creating the pdf should be a matter of running

make images
make latexpdf

Once the build is completed there will be a CounterMitm.pdf file in the build/latex directory. This contains the different approaches.

The sources for the images are stored in .seq files. We used https://bramp.github.io/js-sequence-diagrams/ to turn them into svgs that live in the images directory.

We have not found a good way to automate this yet.