Unauthorized Descrambling of a Random Line Inversion Scrambled TV Signal

Simple techniques for unauthorized descrambling of a random line inversion scrambled television signal are proposed. An analysis of the complexity of the proposed descrambling process is presented and it is shown that high-quality estimates of moderately long encoding sequences can be obtained with reasonable memory and delay. An improvement to the basic scheme which substantially reduces memory requirements with only a slight increase in delay is also evaluated. Finally, it is shown that varying code lengths among a finite number of alternatives does not significantly increase descrambler complexity.