DYNAMIC FEEDBACK ARRANGEMENT SCRAMBLING TECHNIQUE KEYSTREAM GENERATOR

摘要

DYNAMIC FEEDBACK ARRANGEMENT SCRAMBLING TECHNIQUE KEYSTREAM GENERATOR A keystream generator including at least two feedback shift register structures. Each structure has input intermediate and output stages through which data bits are shifted serially in response to a clock signal a plurality of logic elements respectively located between predetermined pairs of register stages means for feeding the data bit shifted from the output stage into the input stage and into predetermined ones of the logic elements in accordance with a polynomial code. The logic elements process a data bit shifted from the preceding stage with the data bit fedback from the output stage in accordance with the polynomial code for input into the succeeding register stage. The structure further includes means for processing the data bits shifted from a predetermined stage of each shift register structure to provide a keystream; and means for varying the polynomial code of at least one of the shift register structures by applying to the logic elements an enabling polynomial code signal that varies in accordance withthe content of data bits shifted from a predetermined register stage. The polynomial code of one of the shift register structures is not varied in response to the polynomial code signal. The bits that cause the polynomial code signal to bevaried are not included in the keystream.