Abstract:
Traffic analysis aims at extracting sensitive information from network traffic patterns, in particular in scenarios where network traffic is encrypted. Traffic analysis has been used to compromise anonymity in anonymous communication systems through various types of attacks, specifically, website fingerprinting (WF), and flow correlation. In this thesis, we explore two approaches to performing traffic analysis on encrypted network traffic: a model-based approach and a data-driven approach.
The model-based approach focuses on establishing statistical models for traffic characteristics which are used to design effective traffic analysis algorithms. We perform model-based traffic analysis on popular Secure Instant Messaging (SIM) applications. Despite using advanced encryption algorithms, such services do not utilize sophisticated obfuscation algorithms and traffic analysis attacks can infer sensitive information from their traffic patterns. In more dynamic and complex systems such as Tor, general-purpose statistical algorithms cannot capture the nature of noise. Hence, we study a second approach, called data-driven. In this approach, we use Deep Neural Networks (DNNs) to design a flow correlation system called DeepCorr to learn a correlation function tailored to Tor's ecosystem.
To mitigate the aforementioned traffic analysis attacks, we investigate different countermeasure techniques. First, we apply obfuscation-based algorithms to both model-based and data-driven approaches. However, normal obfuscation techniques such as delaying packets, are not effective against DNN-based traffic analysis attacks. Therefore, we propose a second defense mechanism based on adversarial examples which are known to degrade the performance of DNNs.
Although data-driven based traffic analysis algorithms show promising performance, they often need a huge amount of data and labeling which may not be accessible easily. For the remaining portion of this thesis, we plan to use semi-supervised and self-supervised algorithms proposed in computer vision to design data-limited traffic analysis algorithms.
Advisor: Amir Houmansadr