Heimdall: A Case for Encrypted Displays

It can be argued that among all the personal devices, a smartphone carries the most private information of one's life. The improved hardware, computing resource, ever-increasing storage, ubiquitous connectivity, and innovative ways of accessing useful information has slowly and steadily integrated smartphones in our lives. Whether it is interacting on social media, planning for the day using productivity apps or getting things done at work, the smartphone screen is the primary gateway between a user and the world of information accessible through the smartphones. There is always a risk of leaking sensitive information while accessing such information on one's smart-device in a public setting. Visual information can be easily taken advantage of by a malicious bystander. Even if the screen is not comprehensible to the human eye, an off-the-shelf recording device can capture the finer details displayed on the victim's smartphone. A popular way of protecting visual information displayed on smartphones is to use privacy screens. However, privacy screens fail to protect visual privacy when the bystander or the recording device is pointed at it directly. To address this issue, in the poster, we propose, Heimdall, an augmented reality (AR) based system. The primary reason for the failure of privacy screens is that the medium used to broadcast the visual information is shared by the intended user and the bystanders. An AR based solution isolates the medium used to receive the visual information by the intended user from any other receiver. The primary guiding force behind the design of Heimdall are as follows: (1) On-demand Privacy Mode: The user should be able to interact with her smartphone without the need of the AR equipment. The user can enable privacy mode when sensitive information needs to be accessed and disable otherwise, and (2) Minimal computation on AR device: We do not assume that the AR device will be capable of performing an intensive computation. AR glasses under Heimdall should be able to stream the user's view and replace it with an augmented view. Heimdall consists of the following three components: (1) Heimdall Client: an application installed on user's smartphone that encrypts or decrypts the screen on user's request, (2) Heimdall AR: an application running on user's AR device that overlays the decrypted visual information on the smartphone, and (3) Heimdall Server: a server software to continuously decrypt an encrypted stream of visual information, stream it back to the AR glass, and relay every interaction made by the user with the AR view to the smartphone device. Figure~\reffig:heimdall_overview shows a high level interaction of all the three components under \heimdall. \beginfigure [t] \includegraphics[width=0.9\columnwidth]Fig/heimdall_oview.pdf \captionThe figure presents a high level overview of the interaction between the three components of \heimdall. labelfig:heimdall_overview \endfigure A typical Heimdall usage scenario is as follows: Alice is at the airport about to board her flight. She receives an important email from work and she decides to respond to the email sooner than later. Alice triggers the privacy mode by invoking \heimdall client on her phone. The screen immediately gets encrypted (garbled for any onlookers.) Alice puts on her AR glass and looks at the phone. She could interact with the email app, read and compose a reply, and send it. After she closes the email app, she taps the AR glass on the side to stop the privacy mode. With the growing number of AR glass products, we find that Heimdall addresses a real-world problem and provides huge value to the users.