Digital watermark screening and detection strategies

• US 6,768,809 B2
• Filed: 02/04/2003
• Issued: 07/27/2004
• Est. Priority Date: 02/14/2000
• Status: Expired due to Term

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Sharma, Ravi K., Rhoads, Geoffrey B.
• Primary Examiner(s): Johns, Andrew W.
• Assistant Examiner(s): NAKHJAVAN, SHERVIN K
• Application Number:
  US10/359,015
• Publication Number:
  US 20030174862A1
• Time in Patent Office: 539 Days
• Field of Search: 382/100, 382/190, 382/195, 382/206, 382/209, 382/219, 382/220, 382/221, 382/224, 382/229, 382/232, 382/233, 382/235, 382/276, 382/278, 382/280, 382/286, 382/287, 713/155, 713/160, 713/161, 713/162, 713/168, 713/176, 713/179, 713/180, 713/181, 713/187, 713/189, 380/200, 380/252, 380/253, 380/254, 380/277, 380/56, 348/465, 348/604
• US Class Current: 382/100
• CPC Class Codes: G06T 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• CPC Class Codes: G06T 1/0064 Geometric transfor invariant watermarking, e.g. affine transform invariant
• CPC Class Codes: G06T 2201/0052 Embedding of the watermark in the frequency domain
• CPC Class Codes: G06T 2201/0065 Extraction of an embedded watermark; Reliable detection
• CPC Class Codes: G11B 20/00086 Circuits for prevention of unauthorised reproduction or copying, e.g. piracy indicating unauthorised use of record carriers in general G11B23/28; scrambling for television signal recording H04N5/913; network architectures or network protocols for network security H04L63/00; cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
• CPC Class Codes: G11B 20/00884 involving a watermark, i.e. a barely perceptible transformation of the original data which can nevertheless be recognised by an algorithm
• CPC Class Codes: H04H 20/31 using in-band signals, e.g. subsonic or cue signal
• CPC Class Codes: H04N 1/32144 embedded in the image data, i.e. enclosed or integrated in the image, e.g. watermark, super-imposed logo or stamp
• CPC Class Codes: H04N 1/32154 Transform domain methods H04N1/32309 takes precedence
• CPC Class Codes: H04N 1/32203 Spatial or amplitude domain methods H04N1/32309 takes precedence
• CPC Class Codes: H04N 1/32288 Multiple embedding, e.g. cocktail embedding, or redundant embedding, e.g. repeating the additional information at a plurality of locations in the image
• CPC Class Codes: H04N 1/32352 Controlling detectability or arrangements to facilitate detection or retrieval of the embedded information, e.g. using markers for decoding, detection or retrieval operations H04N1/32149 and subgroups take precedence
• CPC Class Codes: H04N 19/467 characterised by the embedded information being invisible, e.g. watermarking
• CPC Class Codes: H04N 19/645 by grouping of coefficients into blocks after the transform
• CPC Class Codes: H04N 2005/91335 the copy protection signal being a watermark
• CPC Class Codes: H04N 21/23892 involving embedding information at multiplex stream level, e.g. embedding a watermark at packet level
• CPC Class Codes: H04N 21/426 Internal components of the client ; Characteristics thereof H04N5/44 takes precedence
• CPC Class Codes: H04N 21/44008 involving operations for analysing video streams, e.g. detecting features or characteristics in the video stream arrangements characterised by components specially adapted for monitoring, identification or recognition of video in broadcast systems H04H60/59
• CPC Class Codes: H04N 21/4627 Rights management associated to the content security in data switching network management H04L41/28; security management or policies for network security H04L63/20; access security in wireless networks H04W12/08
• CPC Class Codes: H04N 21/8358 involving watermark protecting executable software by watermarking G06F21/16; image watermarking in general G06T1/0021; watermarks inserted in still images for transmission purposes H04N1/32144; inserting watermarks during video coding H04N19/467
• CPC Class Codes: H04N 2201/3233 : of authentication information, e.g. digital signature, watermark
• CPC Class Codes: H04N 2201/327 : which are undetectable to the naked eye, e.g. embedded codes
• CPC Class Codes: H04N 2201/3284 : for error correction
• CPC Class Codes: H04N 7/163 : by receiver means only

Abstract

To enhance decoding of signals suspected of containing an embedded auxiliary signal, a suspect signal is screened to compute detection values evincing presence and strength of the embedded signal. Screening strategies control detector actions, such as rejecting un-marked signals, improving synchronization of a reader used to extract hidden messages in suspect signals, determining authenticity of signals, and controlling use of the signals.

Claims

1. A method of analyzing a signal suspected of being embedded with an auxiliary signal, the method comprising:

computing detection values from a suspect signal, where each detection value corresponds to a measure of an auxiliary signal embedded in the suspect signal, the auxiliary signal being detected comprises a set of attributes embedded at locations within the suspect signal, and each detection value is a measure of the set of attributes;

computing a relative detection value based on an analysis of two or more of the detection values relative to each other; and

controlling detector action based on the relative detection value.

2. The method of claim 1 wherein the detector action comprises determining whether the suspect signal is authentic.

3. The method of claim 1 where the detection values have corresponding orientation parameters;

and wherein the orientation parameters approximate a spatial or temporal transform that at least a portion of the suspect signal has undergone subsequent to being embedded with an auxiliary signal.

4. A tangible medium on which is stored instructions for performing the method of claim 1.

5. The method of claim 1 wherein the auxiliary signal carries hidden message symbols in the suspect signal.

6. The method of claim 1 wherein the auxiliary signal performs a dual function of carrying a message of two or more symbols and an orientation signal.

7. The method of claim 1 wherein the attributes comprise impulse functions in a transform domain.

8. The method of claim 7 wherein the transform domain comprises a frequency domain.

9. The method of claim 7 including filtering impulse functions detected in the suspect signal as a function of neighboring samples of the detected impulse functions.

10. The method of claim 1 wherein the detection values comprise correlation values.

11. The method of claim 10 wherein the detection values comprise correlation values in a two dimensional correlation.

12. A method of detecting an auxiliary signal embedded in a suspect signal, the embedded auxiliary signal having a set of attributes embedded at locations within the suspect signal, the method comprising:

computing detection values for two or more auxiliary signal candidates in the suspect signal;

evaluating a detection metric based on the detection values; and

controlling a detector action based on the detection metric;

wherein the metric provides a measure of an embedded auxiliary signal that adapts to the suspect signal according to detection values computed from the suspect signal; and

wherein the detection values are each computed as a measure of the set of attributes of the auxiliary signal.

13. The method of claim 12 wherein the detection metric comprise a measure of strength of an auxiliary signal embedded in the suspect signal.

14. The method of claim 13 wherein the measure of strength is used to determine whether the suspect signal is authentic;

and wherein a further detection action is evaluating the metric to determine whether the suspect signal is authentic.

15. The method of claim 12 wherein the detection values comprise correlation values.

16. The method of claim 12 wherein the detection metric is part of a multistage classifier for classifying the suspect signal.

17. The method of claim 16 wherein the classifier classifies the suspect signal as being marked or un-marked with an auxiliary embedded signal.

18. The method of claim 16 wherein the classifier determines whether the suspect signal is authentic.

19. A tangible medium on which is stored instructions for performing the method of claim 12.

20. A detector for analyzing suspect signals having embedded auxiliary signals comprising:

a first screening stage for classifying a suspect signal based on a first detection metric that measures a set of attributes of an auxiliary embedded signal;

a second screening stage for classifying the suspect signal based on a second detection metric that measures a set of attributes of an auxiliary embedded signal;

wherein the first and second stages form a multistage classifier for determining whether a suspect signal is authentic based on measures derived from an embedded auxiliary signal.