substr md5 collision

Question

I need a 4-character hash. At the moment I am taking the first 4 characters of a md5() hash. I am hashing a string which is 80 characters long or less. Will thi

Answer 1

4 first characters contains 4*4 = 16 bits of data, so collision will be definitely at 65536 elements, and, due to birthday attack, it will be found much faster. You should use more bits of hash.