Patent ID: 7487355

Claim:
An encoding data processing apparatus for generating at least one marked version of an original item of material by introducing one of a predetermined set of code words into a copy of said material item, said apparatus comprising: a code word generator operable to generate a first code word of said predetermined set of code words using a pseudo-random number generator, the pseudo-random number generator being operable to generate pseudo-random numbers from which code word coefficients of the first code word are derived, and to generate other code words of the predetermined set from a cyclic shift of the code word coefficients of said first code word; and an encoding processor operable prior to combining a code word of said predetermined set of code words with a copy of said material item, to permute an order of the coefficients of said code word for combining with the copy of the material item in accordance with a permutation code, and to combine the code word coefficients of said code word with said copy of said material item in accordance with said permuted order, wherein said code word generator is operable to generate said pseudo-random numbers for said first code word coefficients from a seed value for initialising said pseudo-random number generator, the seed value uniquely defining said first code word.