Abstract: The method extracts a plurality of blocks from a master image, processes image data corresponding to each block by orthogonal transform, compares coefficients of adjoining blocks with each other, and modifies the order of magnitude of the coefficients, based on bit information to be embedded. The bit information to be embedded is constructed as a basic pattern, which is generated, for example, by the density pattern method. The basic pattern is embedded in image data iteratively. The process of iteratively embedding the basic pattern enhances the resistance against various attacks.

Abstract: The procedure of the present invention specifies predetermined elements included in a matrix F which is obtained by Fourier transform of master image data P0 (step S122), and adds a minute variation ?F of a predetermined magnitude to either a real number array FR or an imaginary number array FI of the predetermined elements (step S124 and S126). Here note that the minute variation ?F should be subtracted from corresponding elements, in order to keep the symmetry of the Fourier spectrum. A resulting image obtained by an inverse transform of the matrix with the minute variation ?F added thereto includes a phase difference pattern W01 that is embedded therein and corresponds to the minute variation ?F. As long as a master image is closed to the public, this embedded pattern can not be taken out of the resulting image nor be deleted by overwriting attacks.

Abstract: The present invention applies a technique, which is characteristic of color images, to embed a digital watermark in a color image and decode the embedded digital watermark. The technique adjusts a color signal transformation matrix by adding or subtracting a digital watermark matrix to or from the color signal transformation matrix in the process of transforming image data of an original color image in an RGB colorimetric system into image data in a YCbCr colorimetric system with the color signal transformation matrix. The digital watermark matrix includes an arbitrary numerical value of real number x, which represents digital watermark information, as an entry thereof and satisfies a condition that a sum of respective entries in each row and in each column is all substantially equal to zero.

Abstract: A color conversion module 42 carries out color conversion of original color image data Grgb from the RGB color system into the CMYK color system to obtain color-converted original color image data Gcmyk (step S104). A DCT module 44 applies DCT (discrete cosine transform) over the whole color-converted original color image data Gcmyk to generate DCT coefficients Dcmyk (step S106). An embedding module 46 embeds the watermark information s into the components C, M, Y, and K of the DCT coefficients Dcmyk (step S108). An IDCT module 48 applies IDCT (inverse discrete cosine transform) onto DCT coefficients D′cmyk with the watermark information s embedded therein to generate embedding-processed color image data G′cmyk (step S110). The color conversion module 42 carries out color conversion of the embedding-processed color image data G′cmyk from the CMYK color system into the RGB color system to obtain embedding-processed color image data G′rgb (step S112).

Abstract: An encoder which encodes a voice in accordance with LD-CELP (Low-Delay Code Excited Linear Prediction) of the ITU-T Recommendation G.728. When a vibration wave is encoded by vector quantization, the code is secretly combined with other data. The encoder stores dividing key data kidx by which 128 types of representative vector data (waveform codes) yj; j=0, 1, . . . , 127 are labeled with 0 or 1 in order from the uppermost bit. If the bit is “0”, the vectors are quantized by using only the waveform codes yj corresponding to the bit “0” of the dividing key data kidx as the selection objects. If the bit is “1”, the vectors are quantized by using only the waveform codes yj corresponding to the bit “1” of the dividing key data kidx as the selection objects. Thus, the outputted voice code is combined with another datum bit.

Abstract: In the process of embedding watermark information in one-dimensional source data, first spread one-dimensional data x(t) is generated by subjecting one-dimensional source data s(t) to spectrum-spreading operation using a PN sequence g(t). This first spread one-dimensional data x(t) then undergoes a modified discrete cosine transformation. A specific frequency component value of the MDCT coefficients is modulated to provide association with the watermark information. The modulated frequency component then undergoes inverse transformation to generate second spread one-dimensional data x′(t). Then, using the same PN sequence in the spreading, the second spread one-dimensional data is subjected to spectrum-despreading to produce digitally watermarked one-dimensional data in which watermark data has been embedded.

Abstract: In a method of coding an electronic text document, the length of a space preceding a word in a line of text data of an electronic document relative to the length of a space following the word is modulated with the value of a bit of signature data. The signature data are thus embedded into the text data of the electronic document, not being easily discernible to illicit readers.