TWC: Small: Collaborative: Advancing Anonymity Against an AS-level Adversary

自主系统(AS)是互联网路由基础设施的关键组成部分。对AS的监控可能会允许对互联网用户进行大规模监控。那些旨在保护在线交流隐私的人可能会求助于像Tor这样的匿名系统，但Tor的设计并不是为了保护他们免受此类级别的对手的攻击。AS级别的对手对设计健壮的匿名系统提出了独特的挑战，并提出了一种与用于设计和研究Tor等系统的威胁模型截然不同的模型。因此，需要新的研究来理解这种威胁并对其进行防御。这个项目正在调查匿名系统的设计，该系统对AS级别的对手具有弹性。首先，该项目旨在量化AS级对手的能力，这些对手是强大的窃听者，也能够主动攻击，但在实践中也有一些限制。其次，该项目正在为匿名系统设计新的路由选择策略，该策略可以限制AS级别的对手可以观察和攻击的匿名流量。最后，该项目正在调查匿名系统如何通过注入虚假的掩护流量和计时延迟来阻碍AS级对手分析加密流量的能力。这项研究的发现和新的匿名系统设计将在大规模在线通信监控的背景下影响到广大用户的隐私。

Autonomous systems (AS) are key building blocks of the Internet's routing infrastructure. Surveillance of AS may allow large-scale monitoring of Internet users. Those who aim to protect the privacy of their online communications may turn to anonymity systems like Tor, but Tor is not designed to protect against such AS-level adversaries. AS-level adversaries present unique challenges for the design of robust anonymity systems and present a very different threat model from the ones used to design and study systems like Tor. Thus, new research is needed to understand this threat and to defend against it. This project is investigating the design of anonymity systems that are resilient against AS-level adversaries. First, the project aims to quantify the capabilities of AS-level adversaries, who are powerful eavesdroppers and also capable of active attacks, but also have some limitations in practice. Second, the project is designing new route-selection strategies for anonymity systems that can limit how much of the anonymized traffic the AS-level adversary can observe and attack. Finally, the project is investigating how anonymity systems can hinder an AS-level adversaries' ability to analyze encrypted traffic by injecting spurious cover traffic and timing delays. The findings and new anonymity system designs from this research will impact the privacy of a broad class of users in the context of forms of large-scale monitoring of online communications.