a system , method and machine - readable medium for pruning an s - random interleaver starting with an interleaver permutation having n elements and alternating between invalidating the last element of the interleaver permutation and invalidating the last element of a corresponding inverse interleaver permutation until the interleaver permutation has k elements , k being less than n , the method being characterized by the use of a reference vector having n flags and comprising : storing a value in an element of the reference vector corresponding to the value of the each element invalidated in the interleaver permutation .