Tamper detection arrangements
Authenticity of a sticker (e.g., a mark-down sticker on a retail item), or integrity of a closure (e.g., on a delivery bag or package), is confirmed by reference to spatial information. In some embodiments a fingerprint is formed from parameters describing spatial placement of a sticker or pattern on a substrate. In some embodiments a digital watermark pattern provides a spatial frame of reference within which one or more other features can be located. In still other embodiments, a package is sealed with a shipping tape marked with a digital watermark. If the tape is slit to tamper with package contents, and is then repaired by an overlay of clear tape, the repair betrays itself by a forensic inspection that reveals a diminution in watermark strength. A great many other features and arrangements are also detailed.
1. A roll of adhesive tape bearing a digital watermark pattern, wherein said digital watermark pattern on a strip of said adhesive tape is tailored to reduce digital watermark readability when said strip is slit along a long axis thereof to yield two parts, and said two parts are thereafter placed in proximity as if not slit, in which reduced digital watermark readability is determined based on an analysis of a synchronization signal component or on a plural-bit payload signal component of the digital watermark pattern.
2. The roll of adhesive tape according to claim 1 in which said adhesive tape is tailored by tailoring dot size, dot count, or dot contrast of marks comprising said digital watermark pattern.
3. The roll of adhesive tape according to claim 1 in which said adhesive tape is tailored by reducing a redundancy by which the plural-bit payload signal component is expressed by said digital watermark pattern.
4. The roll of adhesive tape according to claim 1 in which said adhesive tape is tailored to be made unreadable when said strip is slit along the long axis, and said two parts are thereafter placed in proximity as if not slit.
5. The roll of adhesive tape of claim 1 in which the digital watermark pattern comprises blocks that each includes an instance of the synchronization signal component, and the blocks are spaced along the tape to cause the synchronization signal components of different blocks to be out of phase with one another.
6. The roll of adhesive tape of claim 5 in which the digital watermark pattern comprises incomplete excerpts of complete watermark blocks.
7. The roll of adhesive tape of claim 1 in which the digital watermark pattern comprises the plural-bit payload signal component, and wherein reduced digital watermark readability is determined by assessing a signal strength of the plural-bit payload signal component.
8. The roll of adhesive tape of claim 7 in which the assessing the signal strength of the plural-bit payload signal component includes decoding the message payload from the captured image and re-creating an original embedded bit sequence corresponding to that plural-bit payload signal component.
9. The adhesive tape of claim 1 in which the digital watermark pattern is present on a first of the two parts and is not present on a second of the two parts.
10. The adhesive tape of claim 1 in which the digital watermark pattern comprises the plural-bit payload signal component, and wherein reduced digital watermark readability is determined by assessing a signal strength of the plural-bit payload signal component.
11. Adhesive tape comprising an elongated substrate provided with adhesive and bearing a digital watermark pattern, characterized in that:
said digital watermark pattern is comprised of rows and columns of waxels, wherein neither said rows nor columns of waxels are oriented parallel to a long axis of said tape;
the watermark pattern employs convolutional encoding having a base rate of ⅓, ½, or more;
the watermark pattern is overlaid with additional pattern elements that serve as visual noise;
the watermark pattern comprises blocks that are spaced apart from each other portions of tape without watermark pattern;
the watermark pattern comprises square blocks that each have a side dimension of “X,” and the tape has a width “Y” that is greater than “X,” where “X” and “Y” are positive integers, and the watermark pattern does not fully-span the width of the tape;
the watermark pattern comprises square blocks that each includes a calibration signal, and the blocks are spaced along the tape to cause the calibration signals of different blocks to be out of phase with one another; or
the watermark pattern comprises incomplete excerpts of complete watermark blocks.
12. A roll of adhesive tape according to claim 11 .
13. The adhesive tape of claim 11 in which the watermark pattern is printed on the tape with a glossy ink or varnish.
14. The adhesive tape of claim 11 in which the watermark pattern employs convolutional encoding having a base rate of ⅓, ½, or more.
15. The adhesive tape of claim 11 in which the watermark pattern is overlaid with additional pattern elements that serve as visual noise.
16. The adhesive tape of claim 11 in which the watermark pattern comprises blocks that are spaced apart from each other portions of tape without watermark pattern.
17. The adhesive tape of claim 11 in which the watermark pattern comprises square blocks that each have a side dimension of “X,” and the tape has a width “Y” that is greater than “X,” and the watermark pattern does not fully-span the width of the tape.
18. The adhesive tape of claim 11 in which the watermark pattern comprises square blocks that each includes a calibration signal, and the blocks are spaced along the tape to cause the calibration signals of different blocks to be out of phase with one another.
19. The adhesive tape of claim 11 in which the watermark pattern comprises incomplete excerpts of complete watermark blocks.
20. Adhesive tape bearing a digital watermark pattern, wherein said digital watermark pattern on a strip of said adhesive tape is tailored to reduce digital watermark readability when said strip is tampered with, in which reduced digital watermark readability is determined based on an analysis of a synchronization signal component or on a plural-bit payload signal component of the digital watermark pattern.
21. The adhesive tape of claim 20 in which said adhesive tape is tailored by tailoring dot size, dot count, or dot contrast of marks comprising the digital watermark pattern.
22. The adhesive tape of claim 20 in which said adhesive tape is tailored by reducing a redundancy by which the plural-bit payload signal component is expressed by the digital watermark pattern.
23. The roll of adhesive tape according to claim 20 in which said adhesive tape is tailored to be made unreadable when the strip is cut or broken along a long axis to yield two parts, and the two parts are thereafter placed in proximity of one another as if not cut or broken.
24. The adhesive tape of claim 20 in which the digital watermark pattern comprises blocks that each includes an instance of the synchronization signal component, and the blocks are spaced along the tape to cause the synchronization signal components of different blocks to be out of phase with one another.
25. The adhesive tape of claim 24 in which the digital watermark pattern comprises incomplete excerpts of complete watermark blocks.