Filter Design for Delay-Based Anonymous Communications
This work addresses privacy concerns in anonymous communications for users, but it appears incremental as it applies known filter design techniques to a new domain.
The paper tackles the problem of designing delay-based anonymous communication systems by connecting it to MIMO filter design, obtaining theoretical solutions for optimal filters against adversaries and evaluating them experimentally.
In this work, we address the problem of designing delay-based anonymous communication systems. We consider a timed mix where an eavesdropper wants to learn the communication pattern of the users, and study how the mix must delay the messages so as to increase the adversary's estimation error. We show the connection between this problem and a MIMO system where we want to design the coloring filter that worsens the adversary's estimation of the MIMO channel matrix. We obtain theoretical solutions for the optimal filter against short-term and long-term adversaries, evaluate them with experiments, and show how some properties of filters can be used in the implementation of timed mixes. This opens the door to the application of previously known filter design techniques to anonymous communication systems.