Abstract: A digital data scrambler and descrambler for m parallel synchronized digital data streams, where m is an integer greater than one, is disclosed. The scrambler and descrambler each include m linear sequential filters, each of the m filters being associated with a different one of the m data streams. Each of the scrambler filters include a feedback path and tapping connections to the feedback path and each of the descrambler filters include a feedforward path and tapping connections to the feedforward path. The nature and location of the tapping connections of both the scrambler and descrambler filters are determined in accordance with a polynomial expression which is the same for a matched scrambler and descrambler.