| 摘要 |
A method of embedding data in material, which material is represented by digital samples, the method comprises the steps of: defining a matrix D ; selecting a block of samples having the same dimension as the matrix D , the values of the samples of the block forming a matrix of value C; and embedding a bit b of the data in the block by combining C and D to form a matrix Cs, wherein <F>Cs = C+ D </F> represents a first value of the bit and <F>Cs = C- D </F> represents a second value of the bit. Further steps determine whether the embedded bit results in a valid matrix Cs. In some cases if the matrix would be invalid, a dummy bit may be embedded or matrix C may be clipped. A corresponding method of decoding comprises the steps of: determining the matrix D ; selecting a block the values of the samples in the block forming a matrix Cs, calculating Cs + D and Cs - D ; calculating a function <F>k=<Cs, D ></F>; and decoding the value of the encoded bit; wherein if k>0 then the encoded bit b has the first value and if k<0 the said bit b has the second value. Further steps check whether the bit is valid. The above steganographic ("watermarking") method is preferably applied to image data, for example acting on 8-bit image data such that a block is formed from a number of pixels and elements of the block take values in the range 0-255. The method may apply to video, audio or data material. |
