Spy vs. Spy: Rumor Source Obfuscation

TL;DR

This paper introduces an adaptive diffusion protocol that significantly enhances the anonymity of message sources in social networks, effectively obfuscating the origin even against sophisticated adversaries in both theoretical and real-world settings.

Contribution

The paper proposes a novel adaptive diffusion protocol that achieves near-perfect source obfuscation in infinite regular trees and effectively hides the source in finite, irregular networks like Facebook.

Findings

Achieves near-uniform probability of source identification in infinite regular trees.

Effectively conceals the source in real-world Facebook network samples.

Provides strong source protection even against colluding adversaries.

Abstract

Anonymous messaging platforms, such as Secret and Whisper, have emerged as important social media for sharing one's thoughts without the fear of being judged by friends, family, or the public. Further, such anonymous platforms are crucial in nations with authoritarian governments; the right to free expression and sometimes the personal safety of the author of the message depend on anonymity. Whether for fear of judgment or personal endangerment, it is crucial to keep anonymous the identity of the user who initially posted a sensitive message. In this paper, we consider an adversary who observes a snapshot of the spread of a message at a certain time. Recent advances in rumor source detection shows that the existing messaging protocols are vulnerable against such an adversary. We introduce a novel messaging protocol, which we call adaptive diffusion, and show that it spreads the messages fast and achieves a perfect obfuscation of the source when the underlying contact network is an infinite regular tree: all users with the message are nearly equally likely to have been the origin of the message. Experiments on a sampled Facebook network show that it effectively hides the location of the source even when the graph is finite, irregular and has cycles. We further consider a stronger adversarial model where a subset of colluding users track the reception of messages. We show that the adaptive diffusion provides a strong protection of the anonymity of the source even under this scenario.