Overview of Basic Attack If we randomly selected values for u+v bits the probability that the expression would hold would be exactly 1/2 It is the deviation or bias from the probability of 1/2 for an expression to hold that is exploited in linear cryptanalysis Hence, if the expression holds with probability p, for randomly chosen plaintexts and the corresponding ciphertexts, then the probability bias is pr-1/2 2424 Overview of Basic Attack • If we randomly selected values for u + v bits, the probability that the expression would hold would be exactly 1/2. • It is the deviation or bias from the probability of 1/2 for an expression to hold that is exploited in linear cryptanalysis. • Hence, if the expression holds with probability pL for randomly chosen plaintexts and the corresponding ciphertexts, then the probability bias is pL – 1/2