Watermarking process resilient to collusion attacks

• US 5,664,018 A
• Filed: 03/12/1996
• Issued: 09/02/1997
• Est. Priority Date: 03/12/1996
• Status: Expired due to Term

• Current Assignee: Frank Thomson Leighton
• Original Assignee: Frank Thomson Leighton
• Inventors: Leighton, Frank Thomson
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US08/615,534
• Time in Patent Office: 539 Days
• Field of Search: 380/3, 380/4, 380/23, 380/49, 380/51, 380/54, 380/55, 380/59, 283/113, 283/72, 283/73, 283/74, 283/85, 283/93, 283/57, 283/58, 283/59, 283/901, 283/902, 283/17
• US Class Current: 380/54
• CPC Class Codes: G06F 21/10 Protecting distributed programs or content, e.g. vending or licensing of copyrighted material protection in video systems or pay television H04N7/16 ; Digital rights management [DRM]
• CPC Class Codes: G06F 21/16 Program or content traceability, e.g. by watermarking
• CPC Class Codes: G06T 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• CPC Class Codes: G06T 2201/0063 in relation to collusion attacks, e.g. collusion attack resistant
• CPC Class Codes: G06T 2201/0081 whereby both original and watermarked images are required at decoder, e.g. destination-based, non-blind, non-oblivious
• CPC Class Codes: G06T 2201/0083 whereby only watermarked image required at decoder, e.g. source-based, blind, oblivious
• 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: 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 1/32304 Embedding different sets of additional information
• CPC Class Codes: H04N 2005/91335 the copy protection signal being a watermark
• CPC Class Codes: H04N 2201/3233 of authentication information, e.g. digital signature, watermark
• CPC Class Codes: H04N 2201/3236 Details of authentication information generation
• CPC Class Codes: H04N 2201/324 Selecting a particular authentication information from amongst a plurality of different authentication information
• CPC Class Codes: H04N 2201/327 which are undetectable to the naked eye, e.g. embedded codes
• CPC Class Codes: H04N 5/913 for scrambling ; for copy protection

Abstract

A watermarking procedure wherein each of a set of copies of the work has a slightly-modified form of a "baseline" watermark that is placed within a critical region of the data. The slight variations in the watermarks, however, are not perceptually visible and do not interfere with the work. If multiple persons collude to attempt to create an "illicit" copy of the work (i.e., a copy without a watermark), however, at least one of the modified watermarks is present in the copy, thereby identifying both the illicit copy and the copier.

Claims

1. A watermarking method, comprising the steps of:

(a) generating a digital string from the work to form a baseline watermark;

(b) generating a set of watermarks each having a predetermined relationship to the baseline watermark; and

(c) inserting a respective one of the set of watermarks into a respective copy of the work to create a watermarked copy uniquely identified by the respective one of the set of watermarks; and

(d) repeating step (c) at least m times to create a set of m watermarked copied, each having a different one of the set of watermarks therein, such that if a subset of said m watermarked copies are averaged to produce an illicit copy of the work, at least one of the set of watermarks is detectable in the illicit copy.

2. The method as described in claim 1 wherein the predetermined relationship is a set of random offsets.

3. The method as described in claim 2 wherein the random offsets have a normal distribution having zero mean and unity variance.

4. The method as described in claim 1 wherein the work includes an image.

5. The method as described in claim 1 wherein the work includes an audio signal.

6. The method as described in claim 1 wherein the work includes a video signal.

7. The method as described in claim 1 wherein each of the watermarks is inserted in a critical region of the digital data file.

8. The method as described in claim 1 further including the step of comparing the watermark in the illicit copy with the baseline watermark to determine which possessor of a copy of the work created the illicit copy.

9. A method of securing e work against copying, comprising the steps of:

(a) generating a set of watermarks each comprising a vector of randomly-generated numbers; and

(b) inserting a respective one of the set of watermarks into a respective copy of the work to create a watermarked copy uniquely identified by the respective one of the set of watermarks; and

(c) repeating step (b) at least m times to create a set of m watermarked copies, each having a different one of the set of watermarks therein, such that if a subset of said m watermarked copies are averaged to produce an illicit copy of the work, at least one of the set of watermarks is detectable in the illicit copy.

10. The method as described in claim 9 wherein the work includes an image.

11. The method as described in claim 9 wherein the work includes an audio signal.

12. The method as described in claim 9 wherein the work includes a video signal.

13. The method as described in claim 9 further including the step of comprising the watermark in the illicit copy with the set of watermarks to determine which possessor of a copy of the work created the illicit copy.

14. A method of protecting a work against illicit copying, comprising the steps of:

(a) generating a set of watermarks each having a predetermined relationship to a first watermark for the work; and

(b) inserting a respective one of the set of watermarks into a respective copy of the work to create a watermarked copy uniquely identified by the respective one of the set of watermarks; and

(c) repeating step (b) at least m times to create a set of m watermarked copies, each having a different one of the set of watermarks therein, wherein averaging a pair of said m watermarked copies generates a copy of the work in which at least one of the set of watermarks can be detected.

15. The method as described in claim 14 wherein the first watermark is derived from the work.

16. A method of generating secure copies of a document, comprising the steps of:

(a) generating a set of watermarks each comprising a vector of randomly-generated numbers with a normal distribution having zero means and unity variance;

(b) inserting a respective one of the set of watermarks into a respective copy of the document to create a watermarked copy uniquely identified by the respective one of the set of watermarks; and

(c) repeating step (b) at least m times to create a set of m watermarked copies of the document that the secure against illicit copying.

17. A method of generating secure copies of a document, comprising the steps of:

(a) generating a set of watermarks each comprising a vector of randomly-generated numbers;

(b) inserting a respective one of the set of watermarks into a respective copy of the document to create a watermarked copy uniquely identified by the respective one of the set vectors; and

(c) repeating step (b) at least m times to create a set of m watermarked copies of the document that are secure against illicit copying.