Measuring and Mitigating AS-level Adversaries Against Tor
Measuring and Mitigating AS-level Adversaries Against Tor
复制标题
测量和缓解针对 Tor 的 AS 级对手
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
Michael Schapira
中科院分区：
文献类型：
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作者：
Rishab Nithyanand;Oleksii Starov;Phillipa Gill;A. Zair;Michael Schapira
Tor作为匿名系统的流行使其成为各种攻击的热门目标。我们专注于流量相关攻击，这不再仅仅是学术研究领域，最近披露了NSA和GCHQ积极致力于在实践中实施这些攻击。我们的第一个贡献是一个实证研究，使我们能够获得一个高保真的快照的威胁，在野外的流量相关攻击。我们发现，在Tor创建的所有电路中，高达40%的电路容易受到来自自治系统（AS）级对手的流量关联攻击，42%来自勾结AS级对手，85%来自国家级对手。此外，我们发现，在某些地区（特别是中国和伊朗）存在许多情况下，超过95%的所有可能的电路容易受到相关攻击，强调需要AS感知的中继选择。为了减轻此类攻击的威胁，我们构建了Astoria-一个AS感知的Tor客户端。Astoria利用网络测量的最新发展来执行路径预测和智能中继选择。Astoria将易受攻击的电路数量减少到2%，对抗AS级对手，低于5%，对抗国家级对手。此外，Astoria在整个Tor网络中进行负载平衡，从而不会使任何一组中继过载。
The popularity of Tor as an anonymity system has made it a popular target for a variety of attacks. We focus on traffic correlation attacks, which are no longer solely in the realm of academic research with recent revelations about the NSA and GCHQ actively working to implement them in practice. Our first contribution is an empirical study that allows us to gain a high fidelity snapshot of the threat of traffic correlation attacks in the wild. We find that up to 40% of all circuits created by Tor are vulnerable to attacks by traffic correlation from Autonomous System (AS)-level adversaries, 42% from colluding AS-level adversaries, and 85% from statelevel adversaries. In addition, we find that in some regions (notably, China and Iran) there exist many cases where over 95% of all possible circuits are vulnerable to correlation attacks, emphasizing the need for AS-aware relay-selection. To mitigate the threat of such attacks, we build Astoria‐an AS-aware Tor client. Astoria leverages recent developments in network measurement to perform path-prediction and intelligent relay selection. Astoria reduces the number of vulnerable circuits to 2% against AS-level adversaries, under 5% against colluding AS-level adversaries, and 25% against state-level adversaries. In addition, Astoria load balances across the Tor network so as to not overload any set of relays.