Modern Mix Network Design

I shall explain the renewed interest in mix networks. 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, and discuss how the latency impacts reliability, application design, and user experience. In particular I'll mention how mix networks can be used with messaging applications and crypto currency to resist 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 cover traffic.

There are several historical reasons why mixnets lost popularity and why Tor's onion routing won. Namely, Tor is low latency and really good at being usable. 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: messaging/chat, crypto currency transaction transport, offline browsing, file sharing, bulletine board systems et cetera.

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  • Saturday Aug. 18 15:00 - 16:00 at Speakers Tent