4 ms·That's not half. Its square root of n. By cutting effort in half of 2^n you get only 2^(n-1).by mmozeiko 11y agoThat's not half. Its square root of n. By cutting effort in half of 2^n you get only 2^(n-1).droffel 11y agoThe effective number of bits of entropy are cut in half.mmozeiko 11y agoWell he said "in terms of the effort needed to find a pre-image". For that effort won't be half.