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Method and apparatus for digital watermarking

  • US 6,704,431 B1
  • Filed: 08/31/1999
  • Issued: 03/09/2004
  • Est. Priority Date: 09/04/1998
  • Status: Expired due to Fees
First Claim
Patent Images

1. A method for reading digital watermark data embedded in digital data contents, said method comprising the steps of:

  • receiving said digital data contents;

    determining threshold α

    of reliability of digital watermark data which is read;

    obtaining a binary distribution function F(x) which represents a probability that a number x of ‘

    1’

    bits or ‘

    0’

    bits are included in a bit sequence which is read at random from digital data contents, said binary distribution function F(x) being obtained by using a probability q of reading ‘

    1’

    or ‘

    0’

    in said bit sequence and a repeating number of embedding each bit of digital watermark data;

    reading an ith digital watermark sequence of said digital watermark data from a digital watermark area of said digital data contents;

    calculating the number ki of ‘

    1’

    or ‘

    0’

    included in said digital watermark sequence;

    calculating a probability F(ki) by using said binary distribution function F(x); and

    reconstituting ‘

    1’

    or ‘

    0’

    from ith digital watermark data wi if F(ki)>

    α

    , reconstituting ‘

    0’

    or ‘

    1’

    from ith digital watermark data wi if 1−

    F(ki)>

    α

    , and determining that there is no watermark data or the presence is unknown if both of F(ki)>

    α and

    1−

    F(ki)>

    α

    are not satisfied.

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