Data processing apparatus and method

A detecting data processing apparatus operable to determine whether one or more code words of a predetermined set of code words is present in a suspected version of a material item, the suspected version having been assumed to have been formed by combining a code word with part of the bandwidth of the original material item, said apparatus comprising

• a bandwidth processor operable
• to form a reduced-bandwidth-version of a copy of the original material item and a reduced-bandwidth-version of the suspected version of the material, or a reduced-bandwidth-version of a difference between the original and suspect material items, the bandwidth reduction being arranged to isolate the part of the bandwidth of the material to which the code word may have been combined,
• a recovery processor operable to generate a recovered code word from the reduced-bandwidth-versions of the original and suspect material items or reduced-bandwidth-version difference between the suspect and original material items,
• a correlation processor operable to generate, for each of the code words in the predetermined set of code words a correlation value by correlating the recovered code word with each of the generated code words, and
• a detection processor operable to detect one or more code words from the correlation value for the code word exceeding a predetermined threshold.

A method of determining whether one or more code words of a predetermined set of code words is present in a suspected version of a material item, the suspected version having been assumed to have been formed by combining a code word having a lower-bandwidth with respect to the bandwidth of the original material item, the method comprising

• forming a reduced-bandwidth-version of a copy of the original material item and a reduced-bandwidth-version of the suspected version of the material, or a reduced-bandwidth-version of a difference between the original and suspect material items, the bandwidth reduction being arranged to isolate the part of the bandwidth of the material to which the code word may have been combined,
• generating a recovered code word from the reduced-bandwidth-versions of the original and suspect material items or reduced-bandwidth-version difference between the suspect and original material items,
• generating for each of the code words in the predetermined set of code words a correlation value by correlating the recovered code word with each of the generated code words, and
• detecting one or more code words from the correlation value for the code word exceeding a predetermined threshold.

An apparatus for determining whether one or more code words of a predetermined set of code words is present in a suspected version of a material item, the suspected version having been assumed to have been formed by combining a code word having a lower-bandwidth with respect to the bandwidth of the original material item, the apparatus comprising

• means for forming a reduced-bandwidth-version of a copy of the original material item and a reduced-bandwidth-version of the suspected version of the material, or a reduced-bandwidth-version of a difference between the original and suspect material items, the bandwidth reduction being arranged to isolate the part of the bandwidth of the material to which the code word may have been combined,
• means for generating a recovered code word from the reduced-bandwidth-versions of the original and suspect material items or reduced-bandwidth-version difference between the suspect and original material items,
• means for generating for each of the code words in the predetermined set of code words a correlation value by correlating the recovered code word with each of the generated code words, and
• means for detecting one or more code words from the correlation value for the code word exceeding a predetermined threshold.