A method of generating a pseudorandom data sequence, wherein said pseudorandom data sequence is generated by a procedure for searching for a search pattern in an initial data sequence of N bits, said search procedure comprising the following steps: (a) detecting in said initial data sequence a particular search pattern of r bits that is one of a set of search patterns; (b) determining an output pattern of k bits by an operation that depends on the progress of the preceding step; and repeating the preceding steps (a) and (b) successively to form the pseudorandom data sequence from a succession of output patterns.