Authentication of physical and electronic media objects using digital watermarks

• US 20050135656A1
• Filed: 02/03/2005
• Published: 06/23/2005
• Est. Priority Date: 11/16/1994
• Status: Active Grant

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Seder, Phillip A., Rhoads, Geoffrey B., Carr, J. Scott, Lofgren, Neil, Alattar, Adnan
• Granted Patent: US 7,424,131 B2
• Time in Patent Office: Days
• 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 25/333 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 7/1417 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 1/0028 Adaptive watermarking, e.g. Human Visual System [HVS]-based watermarking
• 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: G06V 30/40 Document-oriented image-based pattern recognition
• CPC Class Codes: G07C 9/253 visually
• 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 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: 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 20/00884 : 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: H04L 2463/103 : applying security measure for protecting copy right protecting software against unauthorised usage in a vending or licensing environment, e.g. protection the software providers copyright G06F21/10; data processing systems or methods, specially adapted for payment schemes, architectures or protocols G06Q20/00; secrecy systems or subscription systems H04N7/16
• 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 1/00846 : based on detection of a dedicated indication, e.g. marks or the like
• CPC Class Codes: H04N 1/00875 : Inhibiting reproduction, e.g. by disabling reading or reproduction apparatus
• 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 1/32154 : Transform domain methods H04N1/32309 takes precedence
• 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 19/467 : characterised by the embedded information being invisible, e.g. watermarking
• 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 2201/327 : 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 2201/3284 : for error correction

Abstract

Digital watermark methods for encoding auxiliary data into a host signal are used to authenticate physical and electronic objects. One such method computes a content specific message dependent on the host signal, encodes the content specific message into a watermark signal, and embeds the watermark in the host signal such that the watermark signal is substantially imperceptible in the host signal. One specific implementation embeds data representing salient features of the host signal into the watermark. For example, for photo IDs, the method embeds the spatial location of salient features of the photo into the watermark. Another implementation computes a semi-sensitive hash of the host signal, such as a low pass filtering of the signal, and embeds the hash into the watermark. The watermark signal may be content dependent by making the watermark key dependent on some attribute of the signal in which the watermark is embedded. Another approach is to make the watermark key dependent on a user or an attribute of the user. Yet another approach is to use multiple watermark components and multiple watermark detection stages that help identify and screen out invalid watermark signals. Another digital watermarking method for authenticating a media object transforms a media signal to a frequency domain comprising an array of frequency coefficients. It selects a first set of frequency coefficients, and alters the selected first set of frequency coefficients so that values of the coefficients in the set correspond to a pattern. The pattern of the media signal is authenticated by comparing a pattern of the values of the frequency coefficients in the set with an expected pattern.

Claims

1. A method for encoding auxiliary data into a host signal comprising:

computing a content specific message dependent on the host signal;

encoding the content specific message into a watermark signal;

embedding the watermark in the host signal such that the watermark signal is substantially imperceptible in the host signal.

2. The method of claim 1 wherein the content specific message represents one or more salient features of the host signal.

3. The method of claim 2 wherein the host signal comprises an image signal, and the salient features include spatial locations of the salient features.

4. The method of claim 3 wherein the image signal comprises a photo of a person, and the salient features include one or more of the following facial features of the person in the photo:

eyes, nose, and mouth;

wherein the photo is authenticated by decoding the spatial locations of the salient features from the watermark and comparing the decoded features with features in the photo.

5. The method of claim 1 wherein the content specific message comprises a semi-sensitive hash of the host signal, where the semi-sensitive hash is defined as a hash that remains substantially unchanged through digital to analog and analog to digital conversion of the host signal.

6. The method of claim 5 wherein the semi-sensitive hash comprises a low pass filtering of the host signal.

7. The method of claim 6 wherein the low pass filtering comprises selecting most significant bits of selected parts of the host signal.

8. The method of claim 5 wherein the host signal comprises a photo of a bearer of a photo identification document that is printed on the document.

9. The method of claim 8 further including:

encoding a unique identifier of the bearer in the watermark signal such that the photo identification document is authenticated by scanning the photo, decoding the unique identifier from the scanned photo, and comparing the unique identifier with an expected unique identifier for the bearer.

10. The method of claim 9 wherein the expected unique identifier is read from a different part of the photo identification document other than the photo.

11. The method of claim 1 wherein the host signal is an image on an object, and the content specific message comprises a unique identifier associated with a bearer of the object.

12. A computer readable medium on which is stored software for performing the method of claim 1.

22. An object bearing a host signal that has been encoded with auxiliary data according to the method of claim 1.

13. A method for authenticating a media object comprising:

transforming a media signal to a frequency domain comprising an array of frequency coefficients;

selecting a first set of frequency coefficients;

altering the selected first set of frequency coefficients so that values of the coefficients in the set correspond to a pattern;

wherein the pattern of the media signal is authenticated by comparing a pattern of the values of the frequency coefficients in the set with an expected pattern.

14. The method of claim 13 wherein the coefficients comprise subband coefficients in a wavelet decomposition of the media signal.

15. The method of claim 13 including:

encoding message symbols into the media signal, where the message symbols each have corresponding coefficient values, the encoding including reading a first coefficient in the first set, selecting a coefficient value among the coefficient values corresponding to a symbol to be encoded that results in a minimum change to the first coefficient, replacing the first coefficient in the first set with the selected coefficient value, and repeating the process of reading, selecting, and replacing coefficients to encode one or more additional message symbols in the first set of coefficients.

16. The method of claim 13 further including:

for each coefficient in the first set, selecting a corresponding coefficient in a corresponding set, and changing values of the coefficients in the first set and the corresponding coefficients in the corresponding set such that the differences between the coefficient values in the first set and the corresponding set form a desired delta pattern.

17. The method of claim 16 wherein the desired delta pattern is a pseudorandom pattern.

18. The method of claim 17 wherein the pseudorandom pattern is generated from a seed number derived from the media signal.

19. The method of claim 16 wherein changing values of the coefficients in the first set and the corresponding set includes replacing a coefficient in the first set with a value computed as an average of the coefficient in the first set and the corresponding coefficient in the second set plus a delta value, and replacing the corresponding coefficient in the corresponding set with the average minus the delta value.

20. A computer readable medium on which is stored software for performing the method of claim 13.

21. An object bearing a media signal that has processed according to the method of claim 13.

23. An identification document including:

a first image embedded with watermark data and printed on the document;

wherein a copy of the first image is embedded with watermark data, and is referenced on the document or encoded into the document; and

wherein the watermark data embedded in the first image and the copy is related in a manner that enables validity of the document to be verified.

24. The identification document of claim 23 wherein the copy of the first image is stored in a machine readable code on the document.

25. The identification document of claim 23 wherein the copy of the first image is compressed before being stored in the machine readable code.

26. The identification document of claim 23 wherein the copy of the first image is stored in a database entry referenced via a database key in the watermark data embedded in the first image printed on the document;

and wherein the database key extracted from the watermark in the first image is used to look up the copy of the first image in the database entry.

27. The identification document of claim 23 wherein the watermark data embedded in the first image printed on the document includes a number that is cryptographically related to a number embedded in the copy of the first image.

28. A method for encoding auxiliary data into a host signal comprising:

computing a content specific message dependent on the host signal;

encoding the content specific message into a watermark signal;

embedding the watermark in the host signal such that the watermark signal is substantially imperceptible in the host signal;

wherein the content specific message includes data representing locations of one or more salient features of the host signal.

29. The method of claim 28 wherein the host signal comprises a photo of a person, and the one or more salient features include one or more of the following facial features of the person in the photo:

eyes, nose, and mouth;

wherein the photo is authenticated by decoding the spatial locations of the salient features from the watermark and comparing the decoded features with features in the photo.

30. A decoder for decoding the locations of the salient features from the host signal that have been embedded into the host signal according to the method of claim 28, and for comparing the decoded locations with locations of features in the host signal to determine authenticity of the host signal.

31. An object carrying an image that has been processed according to the method of claim 28.

32. A method for authenticating a media object comprising:

transforming a media signal to a frequency domain comprising an array of frequency coefficients;

selecting a first set of frequency coefficients;

altering the selected first set of frequency coefficients so that values of the coefficients in the set correspond to a pattern;

wherein the pattern of the media signal is authenticated by comparing a pattern of the values of the frequency coefficients in the set with an expected pattern;

for each coefficient in the first set, selecting a corresponding coefficient in a corresponding set, and changing values of the coefficients in the first set and the corresponding coefficients in the corresponding set such that the differences between the coefficient values in the first set and the corresponding set form a desired delta pattern.

33. A decoder for decoding the pattern from a media signal that has been processed according to claim 32.

34. An object carrying an image that has been processed according to the method of claim 32.

35. A method of encoding a plural symbol auxiliary message into content, comprising:

(a) processing received input content to yield characteristic information related thereto;

(b) defining a plural symbol auxiliary message that includes said characteristic information yielded from the input content;

(c) performing an algorithmic transformation on said plural symbol auxiliary message to yield a watermark signal; and

(d) processing the input content to steganographically convey the watermark signal, yielding encoded content.

36. The method of claim 35 wherein:

said input content includes a text portion and an image portion;

said characteristic information is derived from the text portion; and

said processing comprises embedding the watermark signal in said image portion.

37. The method of claim 35 wherein:

said input content includes a first portion, and a second portion distinct from said first portion;

said characteristic information is based on the first portion; and

said processing comprises embedding the watermark signal in said second portion.

38. The method of claim 35 wherein (d) includes locally adapting the strength of the watermark signal in accordance with local attributes of the input content, to enhance imperceptibility.

39. The method of claim 35 wherein (d) includes embedding the watermark signal substantially throughout the input content, rather than only in isolated portions thereof.

40. The method of claim 35 wherein said encoded content represents image information, and the method further includes printing said encoded content on a substrate.

41. A printed document produced according to the method of claim 40.

42. In a method of digitally watermarking content, the method including performing an algorithmic transformation on a plural symbol auxiliary message to yield a watermark signal, and altering the content in accordance with said watermark signal, an improvement comprising deriving at least certain symbols of said auxiliary message from data representing the content.

43. The method of claim 42 wherein said content comprises graphic indicia.

44. The method of claim 42 wherein the content comprises plural samples, and the method includes:

deriving at least certain symbols of said auxiliary message from a first set of said samples; and

altering a second, different set of said samples in accordance with the watermark signal.

45. A document having content digitally watermarked according to claim 42 printed thereon.