Hardening Tor Hidden Services

Tor is an overlay anonymization network that provides anonymity for clients surfing the web but also allows hosting anonymous services called hidden services. These enable whistleblowers and political activists to express their opinion and resist censorship. Administrating a hidden service is not trivial and requires extensive knowledge because Tor uses a comprehensive protocol and relies on volunteers. Meanwhile, attackers can spend significant resources to decloak them. This thesis aims to improve the security of hidden services by providing practical guidelines and a theoretical architecture. First, vulnerabilities specific to hidden services are analyzed by conducting an academic literature review. To model realistic real-world attackers, court documents are analyzed to determine their procedures. Both literature reviews classify the identified vulnerabilities into general categories. Afterward, a risk assessment process is introduced, and existing risks for hidden services and their operators are determined. The main contributions of this thesis are practical guidelines for hidden service operators and a theoretical architecture. The former provides operators with a good overview of practices to mitigate attacks. The latter is a comprehensive infrastructure that significantly increases the security of hidden services and alleviates problems in the Tor protocol. Afterward, limitations and the transfer into practice are analyzed. Finally, future research possibilities are determined

Performance and Security Improvements for Tor: A Survey

Tor [Dingledine et al. 2004] is the most widely used anonymity network today, serving millions of users on a daily basis using a growing number of volunteer-run routers. Since its deployment in 2003, there have been more than three dozen proposals that aim to improve its performance, security, and unobservability. Given the significance of this research area, our goal is to provide the reader with the state of current research directions and challenges in anonymous communication systems, focusing on the Tor network.We shed light on the design weaknesses and challenges facing the network and point out unresolved issues

Protocol-level Hidden Server Discovery

Abstract—Tor hidden services are commonly used to provide a TCP based service to users without exposing the hidden server’s IP address in order to achieve anonymity and anti-censorship. However, hidden services are currently abused in various ways. Illegal content such as child pornography has been discovered on various Tor hidden servers. In this paper, we propose a protocollevel hidden server discovery approach to locate the Tor hidden server that hosts the illegal website. We investigate the Tor hidden server protocol and develop a hidden server discovery system, which consists of a Tor client, a Tor rendezvous point, and several Tor entry onion routers. We manipulate Tor cells, the basic transmission unit over Tor, at the Tor rendezvous point to generate a protocol-level feature at the entry onion routers. Once our controlled entry onion routers detect such a feature, we can confirm the IP address of the hidden server. We conduct extensive analysis and experiments to demonstrate the feasibility and effectiveness of our approach. Keywords-Anonymous Communication, Tor, Hidden Service I