Proximally Secure Communication in Public Settings Using Specialized Barcodes.

We present a scheme for securely communicating data over close distances in public settings. Exploiting the ubiquity of cameras in modern day devices and the high resolution of displays, our approach provides secure data communication over short distances by using specialized 2-D barcodes along with an adaptive protocol. Specifically, the barcodes carry public data compatible with their conventional design and additionally private data through specialized orientation modulation in the barcode modules. The latter is reliably decoded when the barcodes are captured at close distances but not from farther distances, a property that we call “proximal privacy”. The adaptive protocol dynamically modifies the strength of the orientation modulation until it is just recoverable by the capture camera. We validate our approach via simulations and by using physical devices to display and capture the specialized barcodes.