Method and apparatus for digital watermarking

Abstract

A method for embedding digital watermark data in digital data contents includes the steps of obtaining a frequency coefficient of block data of digital data contents, obtaining a complexity of the block data, obtaining an amount of transformation of the frequency coefficient from the complexity and the digital watermark data, and embedding the digital watermark data by transforming the frequency coefficient. In addition, a method for reading digital watermark data includes the steps of calculating a probability of reading ‘1’ or ‘0’ in a read bit sequence by using a test method on the basis of binary distribution, determining the presence or absence of digital watermark data according to the probability, and reconstituting digital watermark data. Another method includes the steps of performing soft decision in code theory by assigning weights to the digital watermark sequence with a weighting function, and reconstituting digital watermark data.

1 - 4 . (canceled)  
   
   
       5 . A method for reading digital watermark data embedded in digital data contents, said method comprising the steps of: 
 receiving said digital data contents;    dividing said digital data contents into block data;    obtaining a frequency coefficient of said block data; and    generating digital watermark data from said frequency coefficient by using a quantization width corresponding to said frequency coefficient, said quantization width being obtained beforehand according to a manipulation method of said digital data contents.    
   
   
       6 . The method as claimed in  claim 5 , wherein said quantization width is obtained by a method comprising the steps of: 
 dividing first digital data contents into one or a plurality of first block data;    dividing second digital data contents into one or a plurality of second block data, said second digital data contents being obtained by manipulating said first digital data contents with a predetermined manipulation method;    transforming said first block data and said second block data into first frequency coefficients and second frequency coefficients respectively by applying an orthogonal transform;    obtaining difference values between said first frequency coefficients and said second frequency coefficients for each frequency coefficient;    calculating a standard deviation of distribution of said difference values; and    obtaining said quantization width by multiplying said standard deviation by a watermark embedding strength.    
   
   
       7 - 10 . (canceled)  
   
   
       11 . An apparatus for reading digital watermark data embedded in digital data contents, said apparatus comprising: 
 means for receiving said digital data contents;    means for dividing said digital data contents into block data;    means for obtaining a frequency coefficient of said block data; and    means for generating digital watermark data from said frequency coefficient by using a quantization width corresponding to said frequency coefficient, said quantization width being obtained beforehand according to a manipulation method of said digital data contents.    
   
   
       12 . The apparatus as claimed in  claim 11 , wherein said quantization width is obtained by means comprising: 
 means for dividing first digital data contents into one or a plurality of first block data;    means for dividing second digital data contents into one or a plurality of second block data, said second digital data contents being obtained by manipulating said first digital data contents with a predetermined manipulation method;    means for transforming said first block data and said second block data into first frequency coefficients and second frequency coefficients respectively by applying an orthogonal transform;    means for obtaining difference values between said first frequency coefficients and said second frequency coefficients for each frequency coefficient;    means for calculating a standard deviation of distribution of said difference values; and    means for obtaining said quantization width by multiplying said standard deviation by a watermark embedding strength.    
   
   
       13 - 16 . (canceled)  
   
   
       17 . An integrated circuit for reading digital watermark data embedded in digital data contents, said integrated circuit comprising: 
 means for receiving said digital data contents;    means for dividing said digital data contents into block data;    means for obtaining a frequency coefficient of said block data; and    means for generating digital watermark data from said frequency coefficient by using a quantization width corresponding to said frequency coefficient, said quantization width being obtained beforehand according to a manipulation method of said digital data contents.    
   
   
       18 . The integrated circuit as claimed in  claim 17 , wherein said quantization width is obtained by means comprising: 
 means for dividing first digital data contents into one or a plurality of first block data;    means for dividing second digital data contents into one or a plurality of second block data, said second digital data contents being obtained by manipulating said first digital data contents with a predetermined manipulation method;    means for transforming said first block data and said second block data into first frequency coefficients and second frequency coefficients respectively by applying an orthogonal transform;    means for obtaining difference values between said first frequency coefficients and said second frequency coefficients for each frequency coefficient;    means for calculating a standard deviation of distribution of said difference values; and    means for obtaining said quantization width by multiplying said standard deviation by a watermark embedding strength.    
   
   
       19 - 24 . (canceled)  
   
   
       25 - 72 . (canceled)