Katharina Kohls (Ruhr-University Bochum), Kai Jansen (Ruhr-University Bochum), David Rupprecht (Ruhr-University Bochum), Thorsten Holz (Ruhr-University Bochum), Christina Pöpper (New York University Abu Dhabi)

Traffic-analysis attacks are a persisting threat for Tor users. When censors or law enforcement agencies try to identify users, they conduct traffic-confirmation attacks and monitor encrypted transmissions to extract metadata—in combination with routing attacks, these attacks become sufficiently powerful to de-anonymize users. While traffic-analysis attacks are hard to detect and expensive to counter in practice, geographical avoidance provides an option to reject circuits that might be routed through an untrusted area. Unfortunately, recently proposed solutions introduce severe security issues by imprudent design decisions.

In this paper, we approach geographical avoidance starting from a thorough assessment of its challenges. These challenges serve as the foundation for the design of an empirical avoidance concept that considers actual transmission characteristics for justified decisions. Furthermore, we address the problems of untrusted or intransparent ground truth information that hinder a reliable assessment of circuits. Taking these features into account, we conduct an empirical simulation study and compare the performance of our novel avoidance concept with existing
approaches. Our results show that we outperform existing systems by 22 % fewer rejected circuits, which reduces the collateral damage of overly restrictive avoidance decisions. In a second evaluation step, we extend our initial system concept and implement the prototype MultilateraTor. This prototype is the first to satisfy the requirements of a practical deployment, as it maintains Tor’s original level of security, provides reasonable performance, and overcomes the fundamental security flaws of existing systems.

View More Papers

ML-Leaks: Model and Data Independent Membership Inference Attacks and...

Ahmed Salem (CISPA Helmholtz Center for Information Security), Yang Zhang (CISPA Helmholtz Center for Information Security), Mathias Humbert (Swiss Data Science Center, ETH Zurich/EPFL), Pascal Berrang (CISPA Helmholtz Center for Information Security), Mario Fritz (CISPA Helmholtz Center for Information Security), Michael Backes (CISPA Helmholtz Center for Information Security)

Read More

Coconut: Threshold Issuance Selective Disclosure Credentials with Applications to...

Alberto Sonnino (University College London (UCL)), Mustafa Al-Bassam (University College London (UCL)), Shehar Bano (University College London (UCL)), Sarah Meiklejohn (University College London (UCL)), George Danezis (University College London (UCL))

Read More

JavaScript Template Attacks: Automatically Inferring Host Information for Targeted...

Michael Schwarz (Graz University of Technology), Florian Lackner (Graz University of Technology), Daniel Gruss (Graz University of Technology)

Read More

DNS Cache-Based User Tracking

Amit Klein (Bar Ilan University), Benny Pinkas (Bar Ilan University)

Read More