SponsorV 2019 outcomes

Activists, whistleblowers, military and law enforcement, businesses
and governments, and ordinary Internet users are among those that
use anonymity networks to protect their privacy online. Anonymity
networks typically operate as network overlays on top of the Internet,
and aim to separate the notions of network location (where you are
on the network) from network identity (who you are). They permit more
privacy-preserving methods of communication, and are a critical component
of censorship-circumvention systems.

This project explored, designed, and transitioned to practice techniques
that improve the resilience of anonymity systems against realistic but
understudied threats to network anonymity, privacy, and availability.
Much of the existing work in developing defenses for anonymity systems
has focused on finding and correcting weaknesses in the design of the
anonymity protocols. This has led to an arms race in which developers
of anonymity systems harden their software against new attacks,
while adversaries attempt to discover new vulnerabilities. We posit
that adversaries who wish to stay ahead of the curve will transition
to new attacks that target the underlying resources on which anonymity
systems depend. That is, attackers will increasingly focus on alternative
techniques for disrupting anonymous communication. A core goal of this
project was to understand these alternative disruption techniques and
how they affect anonymity networks, and develop robust defenses.

This project led to several groundbreaking improvements in (1) safely
measuring anonymity networks, (2) understanding attacks against such
networks, and (3) developing and deploying robust defenses. In total,
this project led to 14 peer-reviewed papers, nearly all of which were
published at top academic venues (e.g., CCS, USENIX Security, NDSS,
TOPS, VLDB, and IMC). Highlights of this project’s findings include:

- The development of a suite of tools and protocols for safely measuring
anonymity networks. We have significantly advanced the state-of-the-art
in performing privacy-preserving measurements on anonymity networks such
as Tor through three separate research activities: enhancing PrivCount,
robust measurement taking through Historϵ, and unique counting.
We also conducted the most detailed measurement study to date of the
Tor anonymity network.

- The construction, and deployment, of multiple defenses against
denial-of-service attacks. Our defenses were informed by our real-world
measurements of actual attacks against fielded anonymity networks, and
have helped defend anonymity networks against actual (real-world) attacks.

- The introduction and deployment of techniques for better managing
resources in anonymity networks, leading to improved performance and
robustness against flooding-style events.

Making contributions beyond science and technology is a core component
of this project’s goals. Securely and privately communicating is of
tremendous interest to organizations and individuals seeking to freely
access and disseminate information. The research activities completed
during this project significantly improve the ability to communicate
privately online by increasing the resiliency of anonymity networks to
both present-day and future threats. Results from this project have
been disseminated through publications (all of which are posted online)
and through numerous software artifacts that have all been made publicly
available (under open source licenses).

This research project has also fully or partially supported three
Ph.D. students, all of whom have successfully completed their doctoral
studies.