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

Anonymous Multi-Hop Locks for Blockchain Scalability and Interoperability

Giulio Malavolta (Friedrich-Alexander University Erlangen-Nürnberg), Pedro Moreno Sanchez (TU Wien), Clara Schneidewind (TU Wien), Aniket Kate (Purdue University), Matteo Maffei...

Read More

Please Forget Where I Was Last Summer: The Privacy...

Kostas Drakonakis (FORTH, Greece), Panagiotis Ilia (FORTH, Greece), Sotiris Ioannidis (FORTH, Greece), Jason Polakis (University of Illinois at Chicago, USA)

Read More

Neuro-Symbolic Execution: Augmenting Symbolic Execution with Neural Constraints

Shiqi Shen (National University of Singapore), Shweta Shinde (National University of Singapore), Soundarya Ramesh (National University of Singapore), Abhik Roychoudhury...

Read More

DroidCap: OS Support for Capability-based Permissions in Android

Abdallah Dawoud (CISPA Helmholtz Center i.G.), Sven Bugiel (CISPA Helmholtz Center i.G.)

Read More