Plausibly deniable communication solutions built on services popular in Western countries may invite closer scrutiny into the activities of their users in censored countries. This paper investigates the ability of popular single-player games to provide the medium for plausibly deniable communications. We introduce Trilobyte, a system that hides data in game state generated opportunistically during regular game-playing activities, and shares data-hiding state through accounts on gaming platforms. We show that even in the presence of hypothetical censors that inspect game state, Trilobyte can hide up to 5.3 MB of data in game state saved in a one hour gaming session. We investigate the practicality of Trilobyte through surveys with 285 Chinese gamers, and by renting and purchasing thousands of gaming accounts. We find that most investigated games, including games developed in China, allow users to communicate keywords considered sensitive in China, when compressed, encrypted or hidden in game state or chat channels.

Plausibly-deniable (PD) storage systems allow users to securely hide data and plausibly deny its presence when challenged by adversaries who coerce them to provide encryption keys and passwords. However, PD systems need specialized software that renders them detectable by suspicious adversaries questioning the very use of a PD system. To address this fundamental problem, we introduce and formally define the notion of plausible invisibility, preventing adversaries from determining whether a PD system was used in the first place. We develop INVISILINE, a plausibly invisible system resilient against multi-snapshot adversaries that can access the device multiple times. To remain invisible, INVISILINE uses a data layout and encoding that is compatible with the Linux dmcrypt disk encryption subsystem, and stores hidden data in the initialization vectors used by dm-crypt to encrypt public data. INVISILINE ensures that any disk changes that result from changes to the hidden data between adversary snapshots, can be plausibly explained using changes to public data resulting from regular use of dm-crypt. In the presence of adversaries, INVISILINE enables users to access all and only the public data using only dm-crypt. INVISILINE can securely and invisibly hide 19GB on a 1TB disk with no impact on public data I/O, and an average of 4.5MB/s throughput for writing hidden data.

This article deals with providing privacy-preserving access control in Internet of Things (IoT) systems. Here, a user/IoT device requests access to services provided by other IoT devices and multiple requests are combined to a request-specific service chain. An anonymous delegated credential-based system architecture is proposed, where the requester’s identity is not exposed to the services. The article presents the proposed architecture’s various components including the security aspects. Various options for implementing the architecture on resource-full and resource-constrained services are presented. A prototype of the proposed architecture is then implemented using Linux-based containers to emulate the services. Two representative systems, namely, a small-scale home automation system using a short service chain and a large-scale industrial automation system using a long service chain are considered. Timing measurements from the implementation are presented to demonstrate that the architecture is feasible and can be adapted for practical use in large-scale IoT systems.