Ask for Alice: Online Covert Distress Signal in the Presence of a Strong Adversary
Hayyu Imanda, Kasper Rasmussen

TL;DR
This paper introduces a covert distress signaling protocol using TLS handshakes that enables users to secretly alert trusted parties while under surveillance, with minimal overhead and high security against strong adversaries.
Contribution
The paper presents a novel protocol leveraging TLS handshakes for covert distress signals, compatible with existing websites and resistant to detection by powerful adversaries.
Findings
Protocol successfully conceals distress signals within normal TLS traffic
Security analysis proves adversary cannot distinguish distress signals from regular communication
Minimal computational overhead for website participation
Abstract
In this paper we propose a protocol that can be used to covertly send a distress signal through a seemingly normal webserver, even if the adversary is monitoring both the network and the user's device. This allows a user to call for help even when they are in the same physical space as their adversaries. We model such a scenario by introducing a strong adversary model that captures a high degree of access to the user's device and full control over the network. Our model fits into scenarios where a user is under surveillance and wishes to inform a trusted party of the situation. To do this, our method uses existing websites to act as intermediaries between the user and a trusted backend; this enables the user to initiate the distress signal without arousing suspicion, even while being actively monitored. We accomplish this by utilising the TLS handshake to convey additional…
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Taxonomy
TopicsInternet Traffic Analysis and Secure E-voting · Network Security and Intrusion Detection · Advanced Malware Detection Techniques
