Counterfeit imaging

Finally, we would like to note that the algorithm described above for finding a perturbation of a DCT block in the counterfeit image such that its set of eight coefficients satisfy... 

Hyperspectral imaging Vibrational spectroscopy coupled with a spatial analysis (cf. chemical imaging chapter) X Chemical compound distributions Counterfeit detection... 

FIGURE 8 Self-calibrating image comparison for counterfeit identification score images. White higher score. Black lower score. 

Figure 7.7 Classification results for nine turquoise samples. Left digital image right combined VIS/NIR material classification result. Samples a, e and f are true, massive turquoises, sample b is turquoise set in silicate bedrock, h is a true turquoise with different ionic dopants and hence a different colour, sample d is true turquoise powder pressed with a polymeric binder, g is an artificially produced turquoise and c and i are other minerals that look superficially similar to turquoise and are frequently used in counterfeits.

The particular bit extraction procedure described above might be useful from the standpoint of computational efficiency, particularly when applied block-by-block to a compressed JPEG or MPEG bit stream where random access may not be desirable or even possible. However, there is obviously a potential loss of robustness to malicious attacks intended to prevent watermark detection, but this is presumably often not an issue in scenarios where counterfeiting attacks are plausible after all, if a scheme is designed so that the presence of a watermark is required, there is little incentive to remove such a watermark. Furthermore, we note that there is clearly an application-defined trade-off here between efficiency and the robustness of the image dependency. More sophisticated and robust bit extraction procedures are possible, e.g. as described in [12]. The procedure described above was chosen instead for simplicity of exposition. 

In this paper, we described a property of many block-based watermarking schemes, which is that of block-wise independence. Furthermore, we have shown that as a consequence of this property, when using such schemes it may be possible to counterfeit an existing watermark in an unwatermarked image, without either the original watermark owner s consent... 

By making each watermark block dependent upon other blocks in a watermarked image, the problem of watermark counterfeiting quickly becomes computationally infeasible, and the chances of success for an attacker attempting to counterfeit an image containing such a watermark are therefore dramatically reduced. 

Figure 10 Constructed image, containing the counterfeit Wong watermark. 

In forensic science, FTIR microscopy has been used extensively. Rapid chemical imaging of documents and paper currency allows an analyst to distinguish between various inks and the paper itself using ATR mode, which minimizes absorption from cellulose, enabling identification of counterfeit currency. In addition, modern currency often has small security fibers in the paper. These can be visually identified and chemically imaged to confirm authenticity. FTIR microscopy is used to examine paint chips from automobile accidents. An example of a paint chip... 

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