Blindspot: Indistinguishable Anonymous Communications

TL;DR

Blindspot is a high-latency anonymous communication system that leverages social network behaviors to achieve indistinguishability and unobservability, overcoming stochastic bandwidth constraints with a novel routing algorithm.

Contribution

It introduces a new anonymous communication design that encodes messages within social network activity and develops a routing algorithm to handle stochastic bandwidth.

Findings

Achieves indistinguishability under a global active adversary.

Provides reasonable performance for low-volume unobservable communication.

Demonstrates effectiveness using real-world social network data.

Abstract

Communication anonymity is a key requirement for individuals under targeted surveillance. Practical anonymous communications also require indistinguishability - an adversary should be unable to distinguish between anonymised and non-anonymised traffic for a given user. We propose Blindspot, a design for high-latency anonymous communications that offers indistinguishability and unobservability under a (qualified) global active adversary. Blindspot creates anonymous routes between sender-receiver pairs by subliminally encoding messages within the pre-existing communication behaviour of users within a social network. Specifically, the organic image sharing behaviour of users. Thus channel bandwidth depends on the intensity of image sharing behaviour of users along a route. A major challenge we successfully overcome is that routing must be accomplished in the face of significant restrictions - channel bandwidth is stochastic. We show that conventional social network routing strategies do not work. To solve this problem, we propose a novel routing algorithm. We evaluate Blindspot using a real-world dataset. We find that it delivers reasonable results for applications requiring low-volume unobservable communication.