本文分析 Tor 洋葱服务的安全防御状况，发现其安全策略优于明网站点，但在 HTTPS 部署上仍显不足。
摘要：
Tor 洋葱服务是一种匿名托管网站和其他互联网服务的方式。洋葱服务常被用于绕过互联网审查，并向高压政权下的用户提供信息服务。本文对部署在这些洋葱服务上的安全防御进行了分析。洋葱服务往往比明网上的站点具有更好的安全策略。然而，它们在 HTTPS 的部署方面仍然落后，而 HTTPS 是确保此类服务用户安全的一项关键防御。
英文摘要：
Tor Onion Services are a way to host websites and other internet services anonymously. Onion Services are often used to bypass internet censorship and provide information services to users in oppressive regimes. This paper presents an analysis of the security defences deployed on these Onion Services. Onion Services tend to have better security policy than sites on the clear web. However they lag behind in the deployment of HTTPS, a key defence to ensuring the security of users of such services.
Onion services are anonymous network services that are exposed over the Tor network. In contrast to conventional Internet services, onion services are private, generally not indexed by search engines, and use self-certifying domain names that are long and difficult for humans to read. In this paper, we study how people perceive, understand, and use onion services based on data from 17 semi-structured interviews and an online survey of 517 users. We find that users have an incomplete mental model of onion services, use these services for anonymity and have varying trust in onion services in gen…
Recent studies have shown that Tor onion (hidden) service websites are particularly vulnerable to website fingerprinting attacks due to their limited number and sensitive nature. In this work we present a multi-level feature analysis of onion site fingerprintability, considering three state-of-the-art website fingerprinting methods and 482 Tor onion services, making this the largest analysis of this kind completed on onion services to date. Prior studies typically report average performance results for a given website fingerprinting method or countermeasure. We investigate which sites are more…
The current onion routing implementation of Tribler works as expected but throttles the overall throughput of the Tribler system. This article discusses a measuring procedure to reproducibly profile the tunnel implementation so further optimizations of the tunnel community can be made. Our work has been integrated into the Tribler eco-system.
Tor is a communications infrastructure widely used for unfettered and anonymous access to Internet websites. Tor is also used to access sites on the .onion virtual domain. The focus of .onion use and discussion has traditionally been on the offering of hidden services, services that separate their reachability from the identification of their IP addresses. We argue that Tor's .onion system can be used to provide an entirely separate benefit: basic website authentication. We also argue that not only can onionsites provide website authentication, but doing so is easy, fast, cheap, flexible and s…
Onion addresses encode their own public key. They are thus self-authenticating, one of the security and privacy advantages of onion services, which are typically accessed via Tor Browser. Because of the mostly random-looking appearance of onion addresses, a number of onion discovery mechanisms have been created to permit routing to an onion address associated with a more meaningful URL, such as a registered domain name. We describe novel vulnerabilities engendered by onion discovery mechanisms recently introduced by Tor Browser that facilitate hijack and tracking of user connections. We also r…
In the last decade, Tor proved to be a very successful and widely popular system to protect users' anonymity. However, Tor remains a practical system with a variety of limitations, some of which were indeed exploited in the recent past. In particular, Tor's security relies on the fact that a substantial number of its nodes do not misbehave. In this work we introduce, the concept of honey onions, a framework to detect misbehaving Tor relays with HSDir capability. This allows to obtain lower bounds on misbehavior among relays. We propose algorithms to both estimate the number of snooping HSDirs …
In this work we show that Tor is vulnerable to app deanonymization attacks on Android devices through network traffic analysis. For this purpose, we describe a general methodology for performing an attack that allows to deanonymize the apps running on a target smartphone using Tor, which is the victim of the attack. Then, we discuss a Proof-of-Concept, implementing the methodology, that shows how the attack can be performed in practice and allows to assess the deanonymization accuracy that it is possible to achieve. While attacks against Tor anonymity have been already gained considerable atte…
In its more than ten years of existence, the Tor network has seen hundreds of thousands of relays come and go. Each relay maintains several RSA keys, amounting to millions of keys, all archived by The Tor Project. In this paper, we analyze 3.7 million RSA public keys of Tor relays. We (i) check if any relays share prime factors or moduli, (ii) identify relays that use non-standard exponents, (iii) characterize malicious relays that we discovered in the first two steps, and (iv) develop a tool that can determine what onion services fell prey to said malicious relays. Our experiments revealed th…
Several hundred Tor exit relays together push more than 1 GiB/s of network traffic. However, it is easy for exit relays to snoop and tamper with anonymised network traffic and as all relays are run by independent volunteers, not all of them are innocuous. In this paper, we seek to expose malicious exit relays and document their actions. First, we monitored the Tor network after developing a fast and modular exit relay scanner. We implemented several scanning modules for detecting common attacks and used them to probe all exit relays over a period of four months. We discovered numerous maliciou…
The Tor anonymity network is difficult to measure because, if not done carefully, measurements could risk the privacy (and potentially the safety) of the network's users. Recent work has proposed the use of differential privacy and secure aggregation techniques to safely measure Tor, and preliminary proof-of-concept prototype tools have been developed in order to demonstrate the utility of these techniques. In this work, we significantly enhance two such tools--PrivCount and Private Set-Union Cardinality--in order to support the safe exploration of new types of Tor usage behavior that have nev…
In this work, we propose a study on the use of post-quantum cryptographic primitives for the Tor network in order to make it safe in a quantum world. With this aim, the underlying keying material has first been analysed. We observe that breaking the security of the algorithms/protocols that use long- and medium-term keys (usually RSA keys) have the highest impact in security. Therefore, we investigate the cost of quantum-safe variants. These include key generation, key encapsulation and decapsulation. Six different post-quantum cryptographic algorithms that ensure level 1 NIST security are eva…
We introduce and investigate *targeting adversaries* who selectively attack users of Tor or other secure-communication networks. We argue that attacks by such adversaries are more realistic and more significant threats to those most relying on Tor's protection than are attacks in prior analyses of Tor security. Previous research and Tor design decisions have focused on protecting against adversaries who are equally interested in any user of the network. Our adversaries selectively target users---e.g., those who visit a particular website or chat on a particular private channel---and essentiall…
Anonymity networks are providing practical mechanisms to protect its users against censorship by hiding their identity and information content. The best-known anonymity network, The Onion Routing (Tor) network, is however subject to censorship attacks by blocking the public Tor entry routers and a few secret Tor entry points (bridges), thus preventing users to access the Tor. To further advance the evolution of anonymity networks, while addressing censorship attacks, we propose to enhance the well-known multi-circuit Tor technique with linear network coding (LNC) and analyze the resulting cens…
With the rapid increase of threats on the Internet, people are continuously seeking privacy and anonymity. Services such as Bitcoin and Tor were introduced to provide anonymity for online transactions and Web browsing. Due to its pseudonymity model, Bitcoin lacks retroactive operational security, which means historical pieces of information could be used to identify a certain user. We investigate the feasibility of deanonymizing users of Tor hidden services who rely on Bitcoin as a payment method by exploiting public information leaked from online social networks, the Blockchain, and onion web…
Security analysts need to classify, search and correlate numerous images. Automatic classification tools improve the efficiency of such tasks. However, the main resources to develop these tools are datasets, which are introduced and provided by the present paper, for the specific cases of visual correlation of phishing and onion websites. CIRCL's Open-Source tools are the sources of these screenshots, which had been manually verified against personal information leaks. Usage examples of these datasets are proposed in the current paper. These researches directions are, however, not the main con…
