Gamma watermarking

• US 6,740,875 B1
• Filed: 02/11/2000
• Issued: 05/25/2004
• Est. Priority Date: 02/11/1999
• Status: Expired due to Fees

• Current Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Ishikawa, Muriel Y., Wood, Lowell L., Wang, Tzu-Fang, Moody, Kenton J., Lougheed, Ronald W.
• Primary Examiner(s): Lee, John
• Assistant Examiner(s): SOUW, BERNARD E
• Application Number:
  US09/502,859
• Time in Patent Office: 1,565 Days
• Field of Search: 250/302, 250/303, 250/363.01, 250/363.04, 250/370.09, 250/370.1
• US Class Current: 250/302
• CPC Class Codes: B41M 3/14 Security printing securities B42D25/29

Abstract

A covert, gamma-ray “signature” is used as a “watermark” for property identification. This new watermarking technology is based on a unique steganographic or “hidden writing” digital signature, implemented in tiny quantities of gamma-ray-emitting radioisotopic material combinations, generally covertly emplaced on or within an object. This digital signature may be readily recovered at distant future times, by placing a sensitive, high energy-resolution gamma-ray detecting instrument reasonably precisely over the location of the watermark, which location may be known only to the object'"'"'s owner; however, the signature is concealed from all ordinary detection means because its exceedingly low level of activity is obscured by the natural radiation background (including the gamma radiation naturally emanating from the object itself, from cosmic radiation and material surroundings, from human bodies, etc.). The “watermark” is used in object-tagging for establishing object identity, history or ownership. It thus may serve as an aid to law enforcement officials in identifying stolen property and prosecuting theft thereof. Highly effective, potentially very low cost identification-on demand of items of most all types is thus made possible.

Claims

1. A method for tagging an object with a tag, wherein said method comprises affixing at least two radioisotopes to said object, wherein the quantity of each radioisotope of said at least two radioisotopes is controlled to produce a controlled ratio of quantities of each radioisotope relative to the other radioisotopes of said at least two radioisotopes, wherein said controlled ratio encodes digital information within said tag which numeric content can be recovered over time-intervals by use of appropriate detection apparatus, wherein said step of affixing at least two radioisotopes to said object comprises metering said radioisotopes out from at least one solution-containing reservoir of an inkjet printing mechanism operating under algorithmic control to tag said object with a tag in real time.

2. The method of claim 1, wherein at least one radioisotope of said at least two radioisotopes comprising said tag are employed to encode the time-since-creation of said tag.

3. The method of claim 1, wherein said tag is employed for purposes of object identification.

4. The method of claim 1, wherein said quantity of each radioisotope of said at least two radioisotopes does not exceed 1 microCurie of decay activity at the time of creation of said tag.

5. The method of claim 1, wherein said tag comprises a digital bit-string representation encoded with some redundancy.

6. The method of claim 1, wherein at least one radioisotope of said at least two radioisotopes comprises a radionuclide in a specified amount to encode the numerical content of a binary bit-string whose length is at least one bit.

7. The method of claim 1, wherein said object comprises a material object of essentially greater than microscopic scale.

8. The method of claim 5, wherein said redundancy comprises a Hamming error-syndrome built into said tag.

9. The method of claim 1, wherein at least one radioisotope of said at least two radioisotopes comprises radionuclides which are carried on at least one bead of an ion-exchange or zeolite variety.

10. The method of claim 1, wherein at least one radioisotope of said at least two radioisotopes comprises radionuclides which are metered out from at least one solution-containing reservoir of an inkjet-type printing mechanism operating under algorithmic control.

11. The method of claim 1, further comprising, controlling detection of said tag and numeric content read-out processes with a digital computer-implemented algorithmic means.

26. The method of claim 9, further comprising incorporating low-level radioactive tags into label.

27. The method of claim 26, further comprising affixing said label to said object.

28. The method of claim 27, wherein said object comprises something which is often counterfeited.

29. The method of claim 1, wherein said object comprises currency.

30. The method of claim 1, wherein said object comprises media bearing computer software.

31. The method of claim 9, wherein said previously existing objects comprise works of art.

38. The method of claim 2, wherein at least two radioisotopes are employed to encode said time-of-creation of said tag, wherein the ratio of the intensities of two gamma-ray-emitting transitions of two radioisotopes of different half-lives is made to be equal to unity in said watermark, as a time-originating convention, wherein at any later time, the then-observed ratio of line intensities of said transitions constitutes a ‘

clock’

whose ‘

elapsed time-reading’

may be determined as precisely as desired, simply by choosing how long to inspect the clock.

39. The method of claim 2, wherein said time-of-creation of said tag is initiated by placing a fixed, reference amount of a single clock radionuclide in said tag, wherein the age of said tag is determined by the fraction of the reference amount which remains.

40. The method of claim 2, wherein said tag comprises a signature, wherein the content of said signature comprises a sequence of bits in a binary bit-string of dozens of bits in total length, and is encoded by fixing the ratio of the line-intensity of the gamma-radiation from a radioisotope to reference line-intensity, translated back to the time of creation of said tag by use of the time interval encoded in said clock.

41. The method of claim 40, wherein said signature comprises at least two code blocks, wherein the ordering of said code blocks is that bit-string decoded from the lowest-spectral-energy gamma-ray line being sequentially followed by the other code blocks in the order of increasing gamma-ray spectral-energy, one block per gamma-ray line, up to the code block corresponding to the highest spectral-energy gamma-ray line.

12. A method for tagging any object with a tag, wherein said method comprises tagging said object with at least two radioisotopes deposited in a pattern that is to be determined with an appropriate detector-and-collimator arrangement, wherein each radioisotope of said at least two radioisotopes comprises a specified quantity of radionuclides relative to each of the other radionuclides of said at least two radioisotopes to produce a relative mixture of radionuclides, wherein numeric information is encoded in said relative mixture of radionuclides, wherein each radioisotope is metered on said object or upon a tag to be affixed to said object from an ink-jet printer in real time.

13. The method of claim 12, wherein each radioisotope is metered on said object or upon a tag to be affixed to said object using ink-jet printer technology.

14. The method of claim 12, wherein each radioisotope is delivered to said object with the ink typically resident in an ink-jet cartridge of said ink-jet technology, resulting in a watermark visible to said detector-and-collimator arrangement.

15. The method of claim 13, wherein each said radioisotope is delivered from an ink-jet printer cartridge to produce low level radioactive tags incorporated invisibly onto previously existing objects.

16. The method of claim 12, wherein said radionuclides emit penetrating high-energy gamma rays.

17. The method of claim 12, further comprising determining the approximate date at which an object was tagged by measuring the decay of at least one radioisotope of said at least two radioisotope, wherein said at least one radioisotope comprises a precisely known quantity of deposited radionuclide with an appropriate half life.

18. The method of claim 12, further comprising creating two dimensional signature logos detectable as low energy gamma-ray watermarks.

19. The method of claim 18, further comprising identifying said two dimensional signature logos with a modern strip gamma-ray detector.

20. The method of claim 18, further comprising identifying said two-dimensional signature logos with Compton gamma-ray imaging detectors.

24. The method of claim 12, wherein information about said object is encoded in a spatial distribution of each radionuclide relative to the other radionuclides of said at least two radioisotopes.

25. The method of claim 24, wherein said pattern comprises a bar-code.

32. The method of claim 15, wherein said previously existing objects comprise documents.

33. The method of claim 16, further comprising determining the presence of a tagged document in a set of documents by detecting said penetrating high-energy gamma rays.

34. The method of claim 17, wherein at least one radionuclide of said at least two radioisotopes is distributed throughout said tag.

35. The method of claim 17, wherein at least one radionuclide of said at least two radioisotopes is placed in a limited area or volume of said tag.

36. The method of claim 35, wherein said limited area comprises one line of a bar code.

37. The method of claim 36, wherein said bar code is invisible to the unaided eye.

57. The method of claim 14, further comprising incorporating low-level radioactive tags into a label.

58. The method of claim 15, wherein said previously existing object comprise works of art.

21. A method for tagging any object with a tag, wherein said method comprises tagging said object with at least two radioisotopes deposited in a pattern that can be determined with an appropriate detector-and-collimator arrangement, wherein each radioisotope of said at least two radioisotopes comprises a specified quantity of radionuclides relative to each of the other radionuclides of said at least two radioisotopes to produce a relative mixture of radionuclides, wherein numeric information is encoded in said relative mixture of radionuclides, further comprising creating and identifying three-dimensional logo patterns using the gamma-ray tomography.

22. A method for identifying an object, wherein said method comprises directing, a high-energy radioactive ion beam at said object, wherein said ion beam comprises an energy distribution, wherein said energy distribution is used to record a unique signature upon or within said object.

23. The method of claim 22, wherein said object includes an ion implantation depth on said ion beam, wherein said high-energy radioactive ion beam comprises a characteristic beam energy/direction, wherein said characteristic beam energy/direction versus said ion implantation depth of said object provides a unique three-dimensional signature upon or within said object.

42. A gamma watermark, comprising:

a tag comprising at least two radioisotopes, wherein the quantity of each radioisotope of said at least two radioisotopes is controlled to produce a controlled ratio of quantities of each radioisotope relative to the other radioisotopes of said at least two radioisotopes, wherein said controlled ratio encodes digital information within said tag which numeric content that can be recovered over time-intervals by use of appropriate detection apparatus, wherein at least one radioisotope of said at least two radioisotopes comprises radionuclides which are metered out in real time from at least one solution-containing reservoir of an inkjet printing mechanism operated under algorithmic control.

43. The gamma watermark of claim 42, wherein at least one radioisotope of said at least two radioisotopes comprising said tag encode the time-since-creation of said tag.

44. The gamma watermark of claim 42, wherein said tag is affixed to an object for purposes of identification of said object.

45. The gamma watermark of claim 42, wherein said quantity of each radioisotope of said at least two radioisotopes does not exceed 1 microCurie of decay activity at the time of creation of said tag.

46. The gamma watermark of claim 42, wherein said tag comprises a digital bit-string representation encoded with some redundancy.

47. The gamma watermark of claim 43, wherein at least one radioisotope of said at least two radioisotopes comprises a radionuclide in a specified amount to encoded the numerical content of binary bit-string whose length is at least one bit.

48. The gamma watermark of claim 42, wherein said object comprises a material object of essentially greater than microscopic scale.

49. The method of claim 46, wherein said redundancy comprises a Hamming error-syndrome built into said tag.

50. The gamma watermark of claim 42, wherein at least one radioisotope of said at least two radioisotopes comprises radionuclides which are carried on at least one bead selected from a group consisting of an ion-exchange bead and a zeolite bead.

51. The gamma watermark of claim 42, wherein said radionuclides emit penetrating high-energy gamma rays.

52. The gamma watermark of claim 50, wherein said at least one radioisotope comprises a precisely known quantity of deposited radionuclide with in appropriate half life, wherein the appropriate date of emplacing said tag on an object is determinable by measuring the decay of at least one radioisotope of said at least two radioisotopes.

53. The gamma watermark of claim 42, wherein said at least two radioisotopes encode the time-of-creation of said tag and comprises different half-lives, wherein the ratio of the intensities of two gamma-ray-emitting transitions of said at least two radioisotopes is made to be equal to unity to in said tag, as a time-originating convention, wherein at any later time, the then-observed ratio of line intensities of said transitions constitutes a ‘

clock’

whose ‘

elapsed time-reading’

may be determined as precisely as desired, simply by choosing how long to inspect the block.

54. The gamma watermark of claim 42, wherein said tag is encoded with information including the time-of-creation of said tag, wherein said time-of-creation of said tag comprises a fixed, reference amount of a single clock radionuclide in said tag, wherein the age of said tag is determined by the fraction of the reference amount which remains.

55. The gamma watermark of claim 42, wherein said tag comprises a signature, wherein the content of said signature comprises a sequence of bits in a binary bit-string of dozens of bits in total length, and is encoded by fixing the ratio of the line-intensity of the gamma-radiation from a radioisotope to a reference line-intensity, translated back to the time of creation of said tag by use of a time interval encoded in said clock.

56. The gamma watermark of claim 55, wherein said signature comprises at least two code blocks, wherein the ordering of said code blocks is that bit-string decoded from the lowest-spectral-energy gamma-ray line being sequentially followed by the other code blocks in the order of increasing gamma-ray spectral-energy, one block per gamma-ray line, up to the code block corresponding to the highest spectral-energy gamma-ray line.