Abstract: A computer-implemented method of permitting authentication of data added to an initial plurality of unique data items stored on a computer, all of the data items being converted via a one-way function to respective equal length unique digests (or hashes); and the hashes being stored as a linked dataset in which the value of each successive hash is dependent on the value of the previous hash combined with a new hash resulting from the hashing of the most recently added data. The most recent hash in the linked dataset (hash chain) is the cumulative result of all previous hashes in their original sequence, each hash in the dataset being unique to the most recently added data. Each cumulative hash is constructed by incorporating one or more pre-existing cumulative hashes into the source data, before the new hash is calculated.

Abstract: A computer-implemented method of permitting authentication of data added to an initial plurality of unique data items stored on a computer, all of the data items being converted via a one-way function to respective equal length unique digests (or hashes); and the hashes being stored as a linked dataset in which the value of each successive hash is dependent on the value of the previous hash combined with a new hash resulting from the hashing of the most recently added data. The most recent hash in the linked dataset (hash chain) is the cumulative result of all previous hashes in their original sequence, each hash in the dataset being unique to the most recently added data. Each cumulative hash is constructed by incorporating one or more pre-existing cumulative hashes into the source data, before the new hash is calculated.

Abstract: The invention is concerned with the production of filaments or fibers each of which carries a recognizable "signature" (encoding). These filaments or fibers are produced by taking a film (preferably a plastics film) applying a code directly onto the film across the effective width of the film and then dividing the film substantially at right angles to the code into longitudinal filaments, so that the encoding is then present in each of the filament in exactly the same "signature" as in the code applied to the film.