Mix Networks and Cryptocurrency Transaction Transport
During Bitcoin Wednesday on 1 August, 2018, security researcher David Stainton will present the latest advancements in mix networks, which he believes to be the most practical and efficient anonymity technology. This technique invented in 1981 by DigiCash creator David Chaum, has generated renewed interest for its resistance to traffic analysis and network surveillance in relation to messaging and cryptocurrency transactions.
Mix networks are a standard for securely transmitting information across a network through a chain of intermediary servers in such a way that messages are shuffled, sent randomly, and encrypted with public keys corresponding to every step in its route.
David’s talk will cover:
- The basic components of a mix network;
- Its role in resisting active and passive attacks;
- How latency impacts reliability, application design, user experience, and mass adoption;
- How it can be used to circumvent traffic analysis and network surveillance in cryptocurrency and messaging applications;
- The Katzenpost mix network project based on the recently published academic paper, “The Loopix Anonymity System”; and
- How it supports network services and a wide variety of applications such as messaging and chat, cryptocurrency transport, offline browsing, file sharing and bulletin boards.
Like Tor, mix networks protect metadata by using layered encryption and routing packets between a series of independent nodes. However, despite the fact that they inspired Tor and share some superficial similarities with it, they provide vastly more resistance against powerful adversaries, adding both latency and cover traffic, and including partial defense from global passive attacks. Although academics have proposed various anonymity technologies with better threat models than Tor, when latency and cover traffic are added mix networks remain one of the most effective and pragmatic solutions.
There are several historical reasons why mixnets lost popularity and why Tor’s onion routing won: Tor is low latency and very usable while mix networks are essentially unreliable packet switching. Mix networks previously achieved enough mix entropy by using long delays. However, recent insights into the trade off between latency and legitimate and decoy traffic allow us to design effective mix networks that keep latency relatively low.
David Stainton is a security researcher, proponent of the cypherpunks movement and anonymity networks for the purpose of enabling greater freedom of communication. He works on the Panoramix project, where he designs and develops the Katzenpost decryption mix network. He has also volunteered code contributions to Tahoe-LAFS, the Subgraph OS and the Tor Project.