Shared secret arrangements and optical data transfer

• US 9,008,315 B2
• Filed: 05/07/2013
• Issued: 04/14/2015
• Est. Priority Date: 01/20/2012
• Status: Active Grant

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Lord, John D., Stach, John
• Primary Examiner(s): DADA, BEEMNET W
• Application Number:
  US13/888,939
• Publication Number:
  US 20140057676A1
• Time in Patent Office: 707 Days
• US Class Current: 380/270
• CPC Class Codes: H04B 10/11 Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
• CPC Class Codes: H04B 10/1141 One-way transmission
• CPC Class Codes: H04B 10/116 Visible light communication
• CPC Class Codes: H04L 63/0428 wherein the data content is protected, e.g. by encrypting or encapsulating the payload
• CPC Class Codes: H04L 63/083 using passwords cryptographic mechanisms or cryptographic arrangements for entity authentication using a predetermined code H04L9/3226
• CPC Class Codes: H04L 63/18 using different networks or channels, e.g. using out of band channels cryptographic mechanisms or cryptographic arrangements for key distribution involving distinctive intermediate devices or communication paths H04L9/0827; cryptographic mechanisms or cryptographic arrangements for authentication using a plurality of channels H04L9/3215
• CPC Class Codes: H04M 1/003 Telephone sets using electrooptical means in the transmission path
• CPC Class Codes: H04M 1/0264 for a camera module assembly
• CPC Class Codes: H04W 12/04 Key management, e.g. using generic bootstrapping architecture [GBA]
• CPC Class Codes: H04W 12/06 Authentication
• CPC Class Codes: H04W 12/50 Secure pairing of devices
• CPC Class Codes: H04W 12/65 Environment-dependent, e.g. using captured environmental data
• CPC Class Codes: H04W 88/06 adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals

Abstract

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.

Claims

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.

2. The method of claim 1 that includes using information conveyed by said data signal to establish a secure wireless connection between two devices on a network.

3. The method of claim 1 that includes:

processing rows of pixel data of a first color to yield a first time-varying output signal;

processing rows of pixel data of a second color to yield a second time-varying output signal; and

discerning from said output signals a data signal conveying more than 2N symbols per second.

4. The method of claim 3 that further includes processing rows of pixel data of a third color to yield a third time-varying output signal, and discerning from said output signals a data signal conveying more than 3N symbols per second.

5. The method of claim 1 wherein the camera captures rows of imagery at M rows per second, and the method includes discerning from said output signal a data signal conveying more than M symbols per second.

6. The method of claim 5 that includes:

processing rows of pixel data of a first color to yield a first time-varying output signal;

processing rows of pixel data of a second color to yield a second time-varying output signal;

processing rows of pixel data of a third color to yield a third time-varying output signal; and

discerning from said output signals a data signal conveying more than 3M symbols per second.

7. A method of optical signaling, using a portable device camera comprising rows of pixels operated in a rolling shutter fashion, wherein not all parts of a captured image are recorded at the same time, and wherein the camera captures frames of imagery in a video mode at N frames per second, the method comprising 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.

8. The method of claim 7 wherein the camera captures rows of imagery at M rows per second, and the method comprises processing said row data to extract an optical data signal having a data rate greater than M symbols per second.

9. The method of claim 8 that includes processing said row data to extract an optical data signal having a rate of more than 2M symbols per second.

10. A method of optical signaling, using a portable device camera comprising rows of pixels operated in a rolling shutter fashion, wherein not all parts of a captured image are recorded at the same time, and wherein the camera captures frames of imagery in a video mode at N frames per second, the method comprising processing a sequence of data comprising averages of signals from successive rows of pixels, with a pseudo-inverse of a matrix representing an aperture function for the camera, to extract an optical data signal having a data rate greater than N symbols per second.