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Digital watermark

Digital watermark. Alfréd Rényi Institute of Mathematics László Csirmaz Gyula Katona Dezső Miklós Tibor Nemetz. HP ( Compaq ) László Marsovsky Attila Haraszti. Drótposta Ltd. The problem. Current method of identify ing legal or high value documents:

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Digital watermark

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  1. Digital watermark Alfréd Rényi Institute of Mathematics • László Csirmaz • Gyula Katona • Dezső Miklós • Tibor Nemetz HP (Compaq) • László Marsovsky • Attila Haraszti Drótposta Ltd. Digital watermark

  2. The problem • Current method of identifying legal or high value documents: • Producing complicated patterns via printing technology (e.g. banknotes) • Applying holographic markers (e.g. tax stamps) • Specially prepared medium (e.g. embedding metal strips into paper) • At the present time, the most common technique of authentication uses serial numbers or in general alphanumerical strings, rarely combined with pictograms. These can be copied or falsely created. We need a cheap automated solution! Digital watermark

  3. The promise • Finding a cheap solution (mark) ofidentifying legal documents (bank cards, banknotes, stock certificates), which is: • Unique • Very difficult or expensive to copy or duplicate • Can be measured and processed quickly • A couple of hundred bits can be generated as a check code • Goal: • An unforgeable, unique physical identifying mark • A cheap device for reading the mark • An algorithm making a unique and short (200-500 bits long) extract from the picture Digital watermark

  4. Previous achievements Different surfaces – that are actually difficult to copy, but often expensive – are measured, and the results are stored in a central database. The results of the control measurement are compared to the stored data. Digital watermark

  5. Novelties • We do not store results • The mark is cheap, but difficult to copy • IT WORKS Digital watermark

  6. The mark Digital watermark

  7. The reading device Digital watermark

  8. The method • A three-dimensional thin layer, a small mark – which is very difficult or expensive to copy or duplicate – is inseparably attached to the object. This small mark will contain randomly positioned small objects. • Using digital imaging technology we test a photograph of the object, to see that the mark is 3 dimensional, and not just a 2 dimensional copy of a 3 dimensional object. • Using different mathematical algorithmswe generate a unique number (check-code), which can clearly identify the object. Digital watermark

  9. The material Into a thin (typically 0.3-1 mm thick), translucent layer without a light reflecting coating small objects (e.g. glass beads) are embedded. Small (5-20 micrometer) glass beads (balls) coated or not Thin film 0.3-1 mm Digital watermark

  10. Unforgeable Photos taken in diffuse and direct light Digital watermark

  11. Results • The mark is very cheap, as we use a material available anywhere, the price could be around 2-3 cents. • The measuring device is a WEB cam with special optics,which costs 200$-300$ • The stability of the ”code” is excellent. All measurement was in a tolerance of one digit. (plus, minus one pixel!) • The measurement time with non-optimized code is around 10 seconds. • We have developed a method, which does not require storing the code and checking the Hamming distance, but regenerates the code every time on line, using a small piece of redundant information, like a PIN code. Digital watermark

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