Cables Communication
Summary
Cables communication implements secure and anonymous communication using
email-like addresses, pioneered in Liberté Linux.
Cables communication is Liberté’s pivotal component for enabling anyone to
communicate safely and covertly in hostile environments.
What makes cables communication special?
- Anonymity:
Although cables communication is independent of the transport protocol, its
primary purpose is to facilitate message exchange over anonymous networks like
Tor and I2P
- Security:
Cables communication utilizes the
CMS standard
with Perfect forward secrecy-based key management for signing peer keys and
for encrypting messages; Perfect forward
secrecy makes communication resistant to
potential future compromise of user’s certificates; transport-independent
protocol is resistant against short-term and long-term man-in-the-middle
attacks
- Authenticity:
Usernames that are used for communication are certificate hashes, themselves
guaranteeing sender’s authenticity
- Repudiability:
Messages are encrypted and authenticated by deriving shared Diffie-Hellman
keys and MACs, and it is therefore impossible to prove authorship of messages
to third parties after the fact
- Obscurity:
It is impossible to determine whether a host supports cables communication,
unless the username (a certificate hash) is known
- Simplicity:
The protocol is stateless and asynchronous, based on short push messages
with the other end responding with a series of file pulls; there is no
real-time parameters negotiation
- Reliability:
Once a message has been accepted for delivery, it is either delivered to each
destination when both parties are online (with a receipt to the sender), or
the sender is notified about delivery failure after a preset timeframe;
messages are never lost in transactional filesystems
- Transparency:
A regular email client can be used as the user interface, with the
cryptography entirely transparent to the end-user
Project:
GitHub
(issues,
wiki)
How does cables communication work? Initially, user identity certificates
and host identity keys (presently, for Tor
hidden service and I2P
eepSite) are generated, resulting in two permanent
addresses, in the form of gb24hw2h…@5rfvhdhb…dcw6.onion and
gb24hw2h…@ukeu3k5o…dkdq.b32.i2p. That’s it — you can configure an e-mail
client like Claws-Mail to communicate with other
cables communication users with either of these addresses; source and
destination(s) do not need to use the same host identity types either. Once
the source and one of the destinations are online, the message is delivered,
and the source receives an authentic acknowledgement. Signing/encryption and
decryption/verification are handled transparently to the user, and do not rely
on the security of underlying network transport. If the message times out
after several days, the sender is notified as well. Cables communication is
simple, robust, and safe; see also the
Security section.
