Shared secret arrangements and optical data transfer

摘要

Digital data is optically broadcast through an environment by controllably switching the brightness or chrominance of LED solid state lamps, or of other illumination sources (e.g., television screens and backlit computer displays). This optical data channel is useful to convey cryptographic key data by which devices within the environment can authenticate themselves to a secure network. In some embodiments, the optical modulation is sensed by the camera of a smartphone. The row data output by the smartphone's camera sensor is processed to extract the modulated data signal. In some monochrome embodiments, data communication speeds far in excess of the camera's frame rate (e.g., 30/second), or even the camera's row rate (e.g., 14,400/second) are achieved. Still greater rates can be achieved by conveying different data in different chrominance channels. A great number of other features and arrangements are also detailed.

主权项

1. A method employing a smartphone video camera, the method comprising the acts:
using said video camera to capture N frames per second of imagery, each frame comprising plural rows of pixel data; processing said rows of pixel data to yield a time-varying output signal; and discerning from said output signal a data signal conveying more than N symbols per second; wherein said processing and discerning acts comprise processing averages of signals from successive rows of pixels, with a pseudo-inverse of a matrix representing an aperture function for the camera, to discern a data signal having a data rate greater than N symbols per second.