_____ _____ _____ ___
|     |  _  |_   _|_  |  Keep your data,
| | | |     | | | |  _|     trash your meta!
|_|_|_|__|__| |_| |___|

Metadata and privacy

Metadata consist of information that characterizes data. Metadata are used to provide documentation for data products. In essence, metadata answer who, what, when, where, why, and how about every facet of the data that are being documented.

Metadata within a file can tell a lot about you. Cameras record data about when a picture was taken and what camera was used. Office documents like PDF or Office automatically adds author and company information to documents and spreadsheets. Maybe you don't want to disclose those information.

This is precisely the job of mat2: getting rid, as much as possible, of metadata.

mat2 provides:

• a library called libmat2;
• a command line tool called mat2,
• a service menu for Dolphin, KDE's default file manager

If you prefer a regular graphical user interface, you might be interested in Metadata Cleaner, which is using mat2 under the hood.

Requirements

• python3-mutagen for audio support
• python3-gi-cairo and gir1.2-poppler-0.18 for PDF support
• gir1.2-gdkpixbuf-2.0 for images support
• gir1.2-rsvg-2.0 for svg support
• FFmpeg, optionally, for video support
• libimage-exiftool-perl for everything else
• bubblewrap, optionally, for sandboxing

Please note that mat2 requires at least Python3.5.

Requirements setup on macOS (OS X) using Homebrew

brew install exiftool cairo pygobject3 poppler gdk-pixbuf librsvg ffmpeg

Running the test suite

$ python3 -m unittest discover -v

And if you want to see the coverage:

$ python3-coverage run --branch -m unittest discover -s tests/
$ python3-coverage report --include -m --include /libmat2/*'

How to use mat2

usage: mat2 [-h] [-V] [--unknown-members policy] [--inplace] [--no-sandbox]
            [-v] [-l] [--check-dependencies] [-L | -s]
            [files [files ...]]

Metadata anonymisation toolkit 2

positional arguments:
  files                 the files to process

optional arguments:
  -h, --help            show this help message and exit
  -V, --verbose         show more verbose status information
  --unknown-members policy
                        how to handle unknown members of archive-style files
                        (policy should be one of: abort, omit, keep) [Default:
                        abort]
  --inplace             clean in place, without backup
  --no-sandbox          Disable bubblewrap's sandboxing
  -v, --version         show program's version number and exit
  -l, --list            list all supported fileformats
  --check-dependencies  check if mat2 has all the dependencies it needs
  -L, --lightweight     remove SOME metadata
  -s, --show            list harmful metadata detectable by mat2 without
                        removing them

Note that mat2 will not clean files in-place, but will produce, for example, with a file named "myfile.png" a cleaned version named "myfile.cleaned.png".

Web interface

It's possible to run mat2 as a web service, via mat2-web.

Desktop GUI

For GNU/Linux desktops, it's possible to use the Metadata Cleaner GTK application.

Supported formats

The following formats are supported: avi, bmp, css, epub/ncx, flac, gif, jpeg, m4a/mp2/mp3/…, mp4, odc/odf/odg/odi/odp/ods/odt/…, off/opus/oga/spx/…, pdf, png, ppm, pptx/xlsx/docx/…, svg/svgz/…, tar/tar.gz/tar.bz2/tar.xz/…, tiff, torrent, wav, wmv, zip, …

Notes about detecting metadata

While mat2 is doing its very best to display metadata when the --show flag is passed, it doesn't mean that a file is clean from any metadata if mat2 doesn't show any. There is no reliable way to detect every single possible metadata for complex file formats.

This is why you shouldn't rely on metadata's presence to decide if your file must be cleaned or not.

Notes about the lightweight mode

By default, mat2 might alter a bit the data of your files, in order to remove as much metadata as possible. For example, texts in PDF might not be selectable anymore, compressed images might get compressed again, … Since some users might be willing to trade some metadata's presence in exchange of the guarantee that mat2 won't modify the data of their files, there is the -L flag that precisely does that.

Related software

• The first iteration of MAT
• Exiftool
• pdf-redact-tools, that tries to deal with printer dots too.
• pdfparanoia, that removes watermarks from PDF.
• Scrambled Exif, an open-source Android application to remove metadata from pictures.
• Dangerzone, designed to sanitize harmful documents into harmless ones.

Contact

If possible, use the issues system or the mailing list Should a more private contact be needed (eg. for reporting security issues), you can email Julien (jvoisin) Voisin at julien.voisin+mat2@dustri.org, using the gpg key 9FCDEE9E1A381F311EA62A7404D041E8171901CC.

Donations

If you want to donate some money, please give it to Tails.

License

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this program. If not, see http://www.gnu.org/licenses/.

Copyright 2018 Julien (jvoisin) Voisin julien.voisin+mat2@dustri.org
Copyright 2016 Marie-Rose for mat2's logo

The tests/data/dirty_with_nsid.docx file is licensed under GPLv3, and was borrowed from the Calibre project: https://calibre-ebook.com/downloads/demos/demo.docx

The narrated_powerpoint_presentation.pptx file is in the public domain.

Thanks

mat2 wouldn't exist without:

• the Google Summer of Code;
• the fine people from Tails;
• friends

Many thanks to them!