"Robot Steganography"?: Opportunities and Challenges.

Robots are being designed to communicate with people in various public and domestic venues in a helpful, discreet way. Here, we use a speculative approach to shine light on a new concept of robot steganography (RS), that a robot could seek to help vulnerable populations by discreetly warning of potential threats. We first identify some potentially useful scenarios for RS related to safety and security -- concerns that are estimated to cost the world trillions of dollars each year -- with a focus on two kinds of robots, an autonomous vehicle (AV) and a socially assistive humanoid robot (SAR). Next, we propose that existing, powerful, computer-based steganography (CS) approaches can be adopted with little effort in new contexts (SARs), while also pointing out potential benefits of human-like steganography (HS): although less efficient and robust than CS, HS represents a currently-unused form of RS that could also be used to avoid requiring computers or detection by more technically advanced adversaries. This analysis also introduces some unique challenges of RS that arise from message generation, indirect perception, and effects of perspective. For this, we explore some related theoretical and practical concerns for selecting carrier signals and generating messages, also making available some code and a video demo. Finally, we report on checking the current feasibility of the RS concept via a simplified user study, confirming that messages can be hidden in a robot's behaviors. The immediate implication is that RS could help to improve people's lives and mitigate some costly problems -- suggesting the usefulness of further discussion, ideation, and consideration by designers.