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Steganography methods employing embedded calibration data

DC CAFC
  • US 5,636,292 A
  • Filed: 05/08/1995
  • Issued: 06/03/1997
  • Est. Priority Date: 05/08/1995
  • Status: Expired due to Term
First Claim
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1. A method of steganographic encoding characterized by:

  • processing a sampled input signal to produce an output signal having an information signal embedded therein, the sampled input signal corresponding to a two dimensional visual image, each sample of said input signal having a value, the encoding including changing at least certain of said input signal sample values to encode the information signal therein,encoding a calibration signal in the output signal together with said information signal, said calibration signal including data corresponding to a predetermined geometrical pattern, said calibration signal having known properties facilitating identification thereof by a recipient of the encoded signal, said encoded calibration signal being substantially imperceptible to a human viewer of the encoded visual image, said predetermined geometrical pattern including a plurality of rotationally symmetric component pattern elements,wherein there exists at least first and second rotational orientations of said image for which at least one of said component pattern elements, as embedded in the output signal, has the same orientation.

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