In this paper from the 2005 ACM UIST (http://www.acm.org/uist/archive/index.html) conference a system is described that knew when more than one set of eyes were looking at a screen and then tinting the screen red to indicate a possible breech of security. Moreover this system was implemented on a mobile device, thus placing it in public situations where unauthorized eyes were likely to be a problem.

PAPER

"eyeLook:Âusing attention to facilitate mobile media consumption" http://portal.acm.org/citation.cfm?id=1095034.1095050&coll=GUIDE&dl=GUIDE&CFID=43353856&CFTOKEN=45571461

ABSTRACT:

One of the problems with mobile media devices is that they may distract users during critical everyday tasks, such as navigating the streets of a busy city. We addressed this issue in the design of eyeLook: a platform for attention sensitive mobile computing. eyeLook appliances use embedded low cost eyeCONTACT sensors (ECS) to detect when the user looks at the display. We discuss two eyeLook applications, seeTV and seeTXT, that facilitate courteous media consumption in mobile contexts by using the ECS to respond to user attention. seeTV is an attentive mobile video player that automatically pauses content when the user is not looking. seeTXT is an attentive speed reading application that flashes words on the display, advancing text only when the user is looking. By making mobile media devices sensitive to actual user attention, eyeLook allows applications to gracefully transition users between consuming media, and managing life.

I've solved it and posted the answer for y'all. Check it out here: http://c0nn0r.info/blog/2008/12/29/i-pwned-the-fbi-cyphertext-challenge-in-about-45-minutes-using-a-pen-and-paper/

I'm at HOPE right now... Tune in and her me heckle from the audience. I'm the one making fun of Moot from 4chan - you will pics of me there later this weekend harassing him and maybe trying to get a kiss tomorrow night when he's drunk... Mark my words!