A User's Special Touch


Yesterday Volker Roth came back for a visit and to give us a preview of the talk he will give next week at UIST 2010 on his work with Philipp Schmidt and Benjamin Güldenring on The IR Ring: Authenticating users’ touches on a multi-touch display. The work supports multiple users interacting with the same screen at the same time with different access and control permissions. For example, you may want to show me a document on a multi-touch display, but that does not mean you want me to be able to delete that document. Similarly, I may want to show you a particular e-mail I received, without giving you the ability to access my other e-mail messages, or to send one in my name. Roth et al. implemented hardware and software add-ons for a multi-touch display that restrict certain actions to the user wearing the IR ring emitting the appropriate signal. Users wearing different rings have different access and control privileges. In this way, only you can delete your document, and only I can access my other e-mail messages.

Roth and his coauthors frame their work as preventing “pranksters and miscreants” from carrying out “their schemes of fraud and malice.” To me, the work is most compelling as a means to avoid mistakes and to frustrate human curiosity. In most cases, users working on the same display at the same time have some level of mutual trust. But you might be concerned that I might carelessly delete a document of yours, and I might be concerned that you would be tempted to look at other e-mail messages of mine if I turned my back to the display for a minute. Even as a single user interacting with a display, I can see the advantages of using IR rings. For example, only when I wear a special ring would I have superuser privileges. As another example, when I am meeting with one client, I could use a ring to make sure that I don’t inadvertently show another client’s documents to this client (in addition to making sure that if I step out of the room the client cannot access another client’s documents).

The paper is a fun mix of hardware and software. Because the ring uses IR, the  multi-touch display detects the ring in the same way that it detects touches. For this reason, the IR ring approach is an easy and inexpensive way to add authentication of touches to existing multi-touch displays, especially in comparison to other potential approaches such as capacitive coupling. The paper includes lots of fun details about both the hardware and software, including pictures of the interface and the ring’s circuit board. Enjoy taking a look!