In a cipher with good diffusion , flipping an input bit should change each output bit with a probability of one half ( this is termed the Strict Avalanche Criterion ) . In particular , for a randomly chosen input , if one flips the i-th bit , then the probability that the j-th output bit will change should be one half , for any i and j â '' this is termed the strict avalanche criterion . More generally , one may require that flipping a fixed set of bits should change each output bit with probability one half .