Decoding steganographic messages embedded in media signals

• US 6,681,029 B1
• Filed: 07/06/2000
• Issued: 01/20/2004
• Est. Priority Date: 11/18/1993
• Status: Expired due to Term

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Rhoads, Geoffrey B.
• Primary Examiner(s): Couso, Jose L.
• Application Number:
  US09/612,177
• Time in Patent Office: 1,293 Days
• Field of Search: 382/100, 382/112, 382/232, 382/284, 358/3.28, 358/448, 358/450, 380/54, 380/231-234, 380/287, 283/72, 283/73, 283/93, 283/94, 283/113, 283/901, 348/475, 235/494, 340/5.53, 340/5.6, 340/5.65, 340/5.8, 340/5.81, 340/5.83, 340/5.86, 356/71, 902/1, 902/4, 902/6, 713/176, 386/94, 705/1, 705/44
• US Class Current: 382/100
• CPC Class Codes: B42D 25/00 Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof printing processes to produce identification or security features B41M3/14
• CPC Class Codes: B42D 25/23 Identity cards
• CPC Class Codes: B42D 25/333 Watermarks
• CPC Class Codes: G06F 16/955 using information identifiers, e.g. uniform resource locators [URL]
• CPC Class Codes: G06K 19/06037 multi-dimensional coding
• CPC Class Codes: G06K 19/06046 Constructional details
• CPC Class Codes: G06K 19/14 the marking being sensed by radiation
• CPC Class Codes: G06K 19/18 Constructional details
• CPC Class Codes: G06K 2019/06253 for a specific application
• CPC Class Codes: G06K 7/14 using light without selection of wavelength, e.g. sensing reflected white light G06K7/10831 - G06K7/1097 take precedence
• CPC Class Codes: G06K 7/1417 2D bar codes
• CPC Class Codes: G06K 7/1447 extracting optical codes from image or text carrying said optical code
• CPC Class Codes: G06Q 20/341 Active cards, i.e. cards including their own processing means, e.g. including an IC or chip
• CPC Class Codes: G06Q 20/40145 Biometric identity checks
• CPC Class Codes: G06T 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• CPC Class Codes: G06T 1/0057 Compression invariant watermarking
• 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: G06V 30/40 Document-oriented image-based pattern recognition
• CPC Class Codes: G07C 9/253 visually
• CPC Class Codes: G07D 7/0032 : using holograms
• CPC Class Codes: G07D 7/0034 : using watermarks
• CPC Class Codes: G07D 7/004 : using digital security elements, e.g. information coded on a magnetic thread or strip
• CPC Class Codes: G07F 17/16 : for devices exhibiting advertisements, announcements, pictures or the like
• CPC Class Codes: G07F 17/26 : for printing, stamping, franking, typing or teleprinting apparatus ticket printing or the like apparatus G07F17/42
• CPC Class Codes: G07F 7/08 : by coded identity card or credit card or other personal identification means without personal verification means G07F7/02
• CPC Class Codes: G07F 7/086 : by passive credit-cards adapted therefor, e.g. constructive particularities to avoid counterfeiting, e.g. by inclusion of a physical or chemical security-layer for security documents G07D7/00; for the reading of record-carriers in general G06K7/00; for the design of coded credit-cards G06K19/10
• CPC Class Codes: G07F 7/1008 : Active credit-cards provided with means to personalise their use, e.g. with PIN-introduction/comparison system
• CPC Class Codes: G07F 7/1016 : Devices or methods for securing the PIN and other transaction-data, e.g. by encryption arrangements for secret communication, see H04L9/00
• CPC Class Codes: G07F 7/12 : Card verification
• CPC Class Codes: G10L 19/018 : Audio watermarking, i.e. embedding inaudible data in the audio signal
• 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 20/00094 : involving measures which result in a restriction to authorised record carriers
• CPC Class Codes: G11B 20/00115 : wherein the record carrier stores a unique medium identifier
• CPC Class Codes: G11B 20/00166 : involving measures which result in a restriction to authorised contents recorded on or reproduced from a record carrier, e.g. music or software
• CPC Class Codes: G11B 20/00181 : using a content identifier, e.g. an international standard recording code [ISRC] or a digital object identifier [DOI]
• CPC Class Codes: G11B 20/0021 : involving encryption or decryption of contents recorded on or reproduced from a record carrier
• 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: G11B 20/00891 : embedded in audio data
• CPC Class Codes: H04B 1/665 : using psychoacoustic properties of the ear, e.g. masking effect
• CPC Class Codes: H04N 1/00005 : relating to image data
• CPC Class Codes: H04N 1/00037 : Detecting, i.e. determining the occurrence of a predetermined state H04N1/00031 takes precedence
• CPC Class Codes: H04N 1/00079 : remotely
• CPC Class Codes: H04N 1/32122 : in a separate device, e.g. in a memory or on a display separate from image data
• 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 1/3216 : using Fourier transforms
• CPC Class Codes: H04N 1/32203 : Spatial or amplitude domain methods H04N1/32309 takes precedence
• CPC Class Codes: H04N 1/32208 : involving changing the magnitude of selected pixels, e.g. overlay of information or super-imposition H04N1/32219, H04N1/32224 take precedence
• CPC Class Codes: H04N 1/32251 : in multilevel data, e.g. greyscale or continuous tone data
• 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 19/00 : Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
• CPC Class Codes: H04N 19/467 : characterised by the embedded information being invisible, e.g. watermarking
• CPC Class Codes: H04N 2005/91321 : the copy protection signal being a copy protection control signal, e.g. a record inhibit signal
• 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 21/8358 : 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 2201/3205 : of identification information, e.g. name or ID code H04N2201/3209 takes precedence
• CPC Class Codes: H04N 2201/3207 : of an address
• CPC Class Codes: H04N 2201/3225 : of data relating to an image, a page or a document
• CPC Class Codes: H04N 2201/3226 : of identification information or the like, e.g. ID code, index, title, part of an image, reduced-size image
• CPC Class Codes: H04N 2201/3233 : of authentication information, e.g. digital signature, watermark
• CPC Class Codes: H04N 2201/3242 : of processing required or performed, e.g. for reproduction or before recording H04N2201/3256 and subgroups take precedence
• CPC Class Codes: H04N 2201/3249 : data relating to a linked page or object, e.g. hyperlink
• CPC Class Codes: H04N 2201/327 : which are undetectable to the naked eye, e.g. embedded codes
• CPC Class Codes: H04N 2201/3271 : Printing or stamping
• CPC Class Codes: H04N 2201/3274 : Storage or retrieval of prestored additional information
• CPC Class Codes: H04N 2201/328 : Processing of the additional information
• CPC Class Codes: H04N 5/913 : for scrambling ; for copy protection
• CPC Class Codes: H04W 4/12 : Messaging; Mailboxes; Announcements

Abstract

A decoder process reads a message steganographically encoded in a composite signal. One decoding process operates on a potentially modified version of the composite signal. The message is comprised of one or more symbols, each being associated with predetermined signal characteristics. The decoding process correlates these predetermined signal characteristics with the potentially modified composite signal to decode message symbols. Another decoding process analyzes a potentially modified version of the composite signal to gather evidence of signal characteristic associated with a message symbol. Based on the evidence, it determines whether the message symbol is present in the potentially modified version of the composite signal. Yet another decoding process analyzes the composite signal to gather evidence of characteristics associated with the message symbols in the message. Based on the evidence, it estimates message symbols. It compares the estimated message symbols with one or more message symbols known to be included in the message to assess whether the composite signal has a valid message.

Claims

1. A method of decoding a message embedded into a host signal, where the message is encoded in a two-dimensional code signal inserted into the host signal to form a composite signal in which the code signal is hidden and symbols in the message have predetermined signal characteristics such that the code signal is substantially invisible in the host signal, the method comprising:

receiving a potentially modified version of the composite signal; and

correlating the predetermined signal characteristics with the potentially modified composite signal to decode message symbols.

2. The method of claim 1 including:

correlating the predetermined signal characteristics with the potentially modified composite signal to compute a measure of correlation for a message symbol; and

determining whether the message symbol is embedded in the composite signal based on the measure of correlation.

3. The method of claim 1 including:

decoding the message without using the host signal.

6. The method of claim 3 including filtering the potentially modified composite signal to remove portions of the host signal;

and decoding the message from the filtered composite signal.

7. The method of claim 1 wherein the host signal is a video signal and the message is encoded into two or more frames of the video signal.

8. The method of claim 1 wherein the host signal is an image signal.

9. The method of claim 1 wherein the code signal is adapted based on the host signal to make the code signal less perceptible to humans in an output form of the composite signal.

10. The method of claim 1 wherein the code signal is derived in part from the host signal.

11. The method of claim 1 wherein at least part of the decoded message is used to control processing of the composite signal.

12. The method of claim 11 wherein at least part of the decoded message controls a device that processes the composite signal.

13. The method of claim 11 wherein at least part of the decoded message is used to control copying, playback or recording of the composite signal in the device.

14. The method of claim 1 wherein at least part of the decoded message is output on an output device.

15. The method of claim 1 wherein at least part of the decoded message is an address or a reference to an address of a network resource on a computer network.

16. The method of claim 1 wherein at least part of the decoded message is a reference to a database storing information about the host signal.

17. The method of claim 1 including:

correlating the predetermined signal characteristics with the potentially modified composite signal using a matched filter.

18. The method of claim 1 wherein the predetermined signal characteristic comprises a signal vector and including:

correlating the signal vector with the potentially modified composite signal by computing a dot product between the signal vector and at least a portion of the potentially modified composite signal to produce a measure of correlation; and

determining whether a message symbol has been encoded based on the measure of correlation.

19. The method of claim 18 wherein the dot product is computed in a spatial domain.

20. The method of claim 18 wherein the.signal vector is a predetermined noise signal associated with a message symbol or set of symbols.

28. The method of claim 1 comprising:

estimating the two-dimensional code signal by comparing samples of the composite signal with corresponding neighboring samples and deriving an estimate of code signal elements based on a result of the comparison.

4. A method of decoding a message embedded into a host signal, where the message is encoded in a two-dimensional code signal inserted into the host signal to form a composite signal and symbols in the message have predetermined signal characteristics, the method comprising:

receiving a potentially modified version of the composite signal; and

correlating the predetermined signal characteristics with the potentially modified composite signal to decode message symbols;

decoding the message without using the host signal;

estimating at least portions of the host signal; and

removing an estimate of at least portions of the host signal before decoding the message.

5. The method of claim 4 including:

estimating a host signal by computing a local average around discrete samples of the potentially modified composite signal.

29. The method of claim 4 wherein the estimate of the host signal is used to compute an estimate of the two-dimensional code signal.

21. A method of decoding a message steganographically embedded into a host signal, where the message is embedded into the host signal to form a composite signal in which the message is substantially imperceptible by adjusting the host signal to encode a signal characteristic associated with a message symbol, the method comprising:

analyzing a potentially modified version of the composite signal to gather evidence of the characteristic associated with the message symbol, including estimating a steganographic signal embedded in the composite signal by comparing samples of the composite signal with corresponding neighboring samples and deriving an estimate of the steganographic signal based on a result of the comparison; and

based on the evidence, determining whether the message symbol is present in the potentially modified version of the composite signal.

22. The method of claim 21 wherein the evidence includes a measure of correlation and includes:

correlating a signal characteristic associated with a message symbol with the potentially modified version of the composite signal.

23. The method of claim 21 wherein the message includes two or more symbols embedded into the host signal, each being associated with a distinct signal characteristic, and includes:

analyzing a potentially modified version of the composite signal to gather evidence of the characteristics associated with the message symbols;

based on the evidence, determining whether the message symbols are present in the potentially modified version of the composite signal; and

reconstructing at least a portion of the message from message symbols determined to be present in the potentially modified version of the composite signal.

24. The method of claim 21 wherein the signal characteristic is a two-dimensional code signal.

25. A method of decoding a message steganographically embedded into a host signal, where the message is embedded into the host signal to form a composite signal in which the message is substantially imperceptible by adjusting the host signal to encode signal characteristics associated with message symbols, the method comprising:

analyzing a potentially modified version of the composite signal to gather evidence of the characteristics associated with the message symbols in the message, including estimating at least portions of the host signal, and removing an estimate of at least portions of the host signal to compute an estimate of steganographically embedded data; and

based on the evidence, estimating message symbols in the steganographically embedded data; and

comparing the estimated message symbols with one or more message symbols known to be included in the message to assess whether the potentially modified version of the composite signal has a valid message.

26. The method of claim 25 wherein the message includes at least one known message symbol and one or more other message symbols.

27. The method of claim 25 wherein the host signal has two or more dimensions, and the message is embedded in the host signal so as to extend over two or more dimensions of the host signal.

30. The method of claim 25 wherein the estimate of the steganographically embedded data is derived by comparing samples of the composite signal with corresponding samples of the estimate of the host signal.