Captchat: A Messaging Tool to Frustrate Ubiquitous Surveillance

Dunphy, P; Schoning, J; Nicholson, J; Olivier, P

doi:10.1145/2702613.2732515

Captchat: A Messaging Tool to Frustrate Ubiquitous Surveillance

Lookup NU author(s): Dr Paul Dunphy, James Nicholson, Professor Patrick Olivier ORCiD

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Abstract

Copyright 2015 ACM. There is currently a widespread uncertainty regarding the ability of citizens to control privacy online in the face of ubiquitous surveillance. This is a huge and complex societal problem. Despite the multi-faceted nature of the problem, we propose that HCI researchers can still make a positive contribution in this space through the design of technologies that support citizens to engage with issues of surveillance. In this paper we describe the design of a messaging application called Captchat. Captchat enables people to send everyday messages embedded into images, with the added ability to apply visual distortions to the message to resemble an online CAPTCHA. We propose the chief benefit would be that Captchat messages (with potentially "one-time" distortions) can increase the difficulty for algorithms to index private messages and necessitate the involvement of much more costly human labor in the surveillance process. We developed a prototype and conducted a user study; the results suggest that people were likely to create Captchat messages that were difficult to index for an OCR package but still easy to understand by humans, even without explicit instructions to interact 'securely' with the application. While more work is still required to understand the limitations of Captchat, we hope it can open discussion on how HCI researchers can respond to the challenges faced from ubiquitous surveillance.