Patent ID: 7881492

Claim:
An electronic watermark embedding apparatus comprising: input image storage means for storing a pixel matrix G with n rows and n columns of an input image; eigenvalue-and-vector calculating means for acquiring eigenvalues s 1 to s n (s 1 >s 2 > . . . >s n ) and eigenvectors p 1 to p n of the pixel matrix G read from the input image storage means; eigenvalue correcting means for selecting at least one pair of eigenvalues (s i ,s j ) having different values from the acquired eigenvalues s 1 to s n and correcting the acquired eigenvalues s 1 to s n such that the values of the selected pair can be equal; means for creating a Jordan-normal-form matrix S w having the corrected eigenvalues as diagonal elements and 1 as one of the nondiagonal elements corresponding to the selected pair; means for outputting the acquired eigenvectors p 1 to p n as electronic watermark key information; means for performing the inverse transform of diagonalization computing on the created matrix S w by using the acquired eigenvectors p 1 to p n to create a pixel matrix G w with n rows and n columns thereby and outputting it as an electronic-watermark-embedded image of the input image.