conference logo

Playlist "Chaos Communication Camp 2019"

Introduction to Mix Networks and Katzenpost

David Stainton and mo

This talk will introduce the fundamental concepts of mix networks as
well as the Katzenpost mix network free software project. We are not
just implementing a new mix network but starting a new anonymity
movement and we welcome others to join us! Like Tor, mix networks
protect metadata by using layered encryption and routing packets
between a series of independent nodes. Mix networks resist vastly more
powerful adversary models than Tor though, including partial defense
against global passive adversaries. In so doing, mix networks add both
latency and cover traffic. I shall outline the basic components of a
mix network, touch on their roles in resisting active and passive
attacks. In particular I'll mention how mix networks can be used with
encrypted messaging applications and crypto currency to resist global
network surveillance and traffic analysis.

Academics have proposed various anonymity technologies with far
stronger threat models than Tor, but by far the most practical and
efficient option remains mix networks, which date to the founding of
anonymity research by David Chaum in 1981. Tor was inspired by mix
networks and shares some superficial similarities, but mix networks'
are vastly stronger if they judiciously add latency and decoy traffic.

There are several historical reasons why mixnets lost popularity and
why Tor's onion routing won. Namely, Tor is low latency and can be
used to browse the web. This is in contrast to mix networks which are
essentially an unreliable packet switching network. Historically mix
networks achieved enough mix entropy by using long delays whereas it
is becoming more widely understood that there exists a trade off
between legit traffic, decoy traffic and latency. After this
introduction to mix networks I'll talk a bit about the Katzenpost mix
network software project which is based off of the recently published
academic paper "The Loopix Anonymity System". These new insights into
mix network designs allow modern mix networks to make the correct
design trade offs so that we can keep the latency relatively
low. Historically high latency and unreliability has been a major
obstacle to mass adoption. I shall explain how Katzenpost solves both
of these problems and allows developers to easily add network services
to the mix network to support a wide variety of client applications
including but not limited to: encrypted messaging, crypto currency
transaction transport, offline browsing and, transporting client
interactions with Distributed Hash Tables and Conflict Free
Replicating Data Types et cetera.