Definition
Cryptographic Hash Function
A cryptographic hash function is a hash function satisfying additional properties required for security applications:
- One-way: easy to compute the hash for a given input, infeasible to compute an input that maps to a given hash value
- Uniformity: the probability of obtaining a particular
-bit output for a random input should be - Diffusion: each bit of the input message should affect as many output bits as possible
- Weak collision resistance: given a message
and a hash function , it is infeasible to find another message such that - Strong collision resistance: given a hash function
, it is infeasible to find two different messages such that - Near-collision resistance: given a hash function
, it is infeasible to find two different messages such that their hashes differ only in a few bits