8.2 KiB
Tomb User Manual
- Why Tomb?
- Getting Started
- Tombs in your pockets
- Tombs in the clouds
- Advanced techniques
- Credits
- Remote tombs
Abstract: Tomb is a cryptographic application that helps you store private and confidential data into volumes secured by keys and passwords. It works on GNU/Linux operating systems, both for desktop and remote shell usage, presenting users with with an intuitive command-line interface. This manual will outline the basic usage of Tomb, from getting started to the everyday drill, plus tips and recommendations on advanced usage and data safety.
[TABLE-OF-CONTENTS]
Why Tomb?
Privacy and freedom
The internet offers plenty of free services, on the wave of the Web2.0 fuzz and the community boom, while all private informations are hosted on servers owned by global corporations and monopolies.
It is important to keep in mind that no-one else better than you can ensure the privacy of your personal data. Server hosted services and web integrated technologies gather all data into huge information pools that are made available to established economical and cultural regimes.
This software urges you to reflect on the importance of your privacy. World is full of prevarication and political imprisonments, war rages in several places and media is mainly used for propaganda by the powers in charge. Some of us face the dangers of being tracked by oppressors opposing our self definition, independent thinking and resistance to omologation.
"The distinction between what is public and what is private is becoming more and more blurred with the increasing intrusiveness of the media and advances in electronic technology. While this distinction is always the outcome of continuous cultural negotiation, it continues to be critical, for where nothing is private, democracy becomes impossible."
(from Privacy Conference, Social Research, New School University)
Who needs Tomb
Our target community are GNU/Linux users with no time to click around, sometimes using old or borrowed computers, operating in places endangered by conflict where a leak of personal data can be a threat.
For example, if one doesn't owns a laptop or simply doesn't likes to carry a computer around, Tomb functions as a secure on-line and off-line storage for data and programs. On a desktop computer, Tomb can store some files locked using a key which can be carried with you and hidden into images. Tomb can do that also on a remote shell and setup a ready environment every time its opened by mounting personal directories in place using bind hooks.
Under the Hood
Tomb provides military-grade encryption on your fingertips, fostering best practices and saving users the time to look into the details of LUKS volumes and cryptsetup. Rather than reinventing the wheel, Tomb relies only on peer-reviewed, free and open source software components: at its core is DM-Crypt1 which is part of the Linux kernel architecture.
For better clarity, Tomb is written in shell script and its code can be reviewed any time. More specifically, Tomb is written in ZSh, but can be used also from Bash.
Tomb is written in a way that promotes privilege separation: a system can let its users execute the script as root, resting assured that it will drop privileges when unneeded.
The key files in Tomb are generated using high entropy random and protected via symmetric cryptography using GnuPG. The combination of a key and its password allow to open a tomb: the key contents are used to encrypt LUKS volumes mounted in loopback. The password is asked using Pinentry programs to protect from common software keyloggers and measures are taken to avoid leaving traces on any permanent storage.
Yet another tool?
∈dexentry{dyne:bolic}
Tomb is an evolution of the Nesting tool developed in 2001 for the Dyne:bolic GNU/Linux distribution: a nomadic system to encrypt the Home directory of users and have it ready for use on different machines. At that time, Tomb was the first secure implementation of what nowadays we call persistent storage in live operating systems.
Later on we've felt the urgency to publishing this mechanism for other operating systems than dyne:bolic since the current situation in personal desktop encryption is far from optimal. Let's have a look.
∈dexentry{truecrypt} TrueCrypt makes use of statically linked libraries so that its code is hard to audit, plus is not considered free by free operating system distributors because of liability reasons, see Debian, Ubuntu, Suse, Gentoo and Fedora.
∈dexentry{cryptkeeper} Cryptkeeper is the best alternative to Tomb out there and its main advantage consists in not needing root access on the machine it's being used. But Cryptkeeper still has drawbacks: it uses EncFS which implements weaker encryption than dm-crypt and it doesn't promotes the separated storage of keys.
At last, the Encrypted home mechanisms on operating systems as Debian and Ubuntu adopt encryption algorithms as strong as Tomb does, but they need to be configured when the machine is installed, they cannot be easily transported and again they don't promote separated storage of keys.
With Tomb we try to overcome all these limitations providing strong encryption, encouraging users to separate keys from data and letting them transport tombs around easily. Also to facilitate auditing and customization we intend to:
- write code that is short, readable and well documented
- use commonly available shared components whenever possible
- facilitate integration into desktop and graphical interfaces
- keep the development process open and distributed using Git
- distribute Tomb under the GNU General Public License v3
If you believe this is a worthy effort, you are welcome to support it.
TODO Getting Started
work on contents in the crunchbang howto
Tombs in your pockets
Tombs in the clouds
when creating a tomb make sure the device mapper is loaded among kernel modules or creation will fail and leave you in the dust.
modprobe dm_mod modprobe dm_crypt
to create a tomb on a server (even VPS) is possible, but the problem becomes the little available entropy. in order to fix this one can use EGD the Entropy Gathering Daemon.
on Debian, do:
sudo aptitude install libdigest-sha1-perl sudo aptitude install ekeyd-egd-linux
/etc/default/ekeyd-egd-linux
wget http://egd.sourceforge.net/
perl ./egd.pl
/etc/init.d/ekeyd-egd-linux start
Advanced techniques
Credits
The development of Tomb was not supported by any governative or non-governative organization, its author and maintainer is an European citizen residing in the Netherlands. Test cases for the development Tomb have been analyzed through active exchange with the needs of various activist communities, in particular the Italian Hackmeeting community and the mestizo community of southern Mexico, Chapas and Oaxaca.