<Dl> <Dd> Given an input m, it should be difficult to find a different input m such that hash (m) = hash (m). Functions that lack this property are vulnerable to second - preimage attacks . </Dd> </Dl> <Dd> Given an input m, it should be difficult to find a different input m such that hash (m) = hash (m). Functions that lack this property are vulnerable to second - preimage attacks . </Dd> <Li> Collision resistance <Dl> <Dd> It should be difficult to find two different messages m and m such that hash (m) = hash (m). Such a pair is called a cryptographic hash collision . This property is sometimes referred to as strong collision resistance . It requires a hash value at least twice as long as that required for pre-image resistance; otherwise collisions may be found by a birthday attack . </Dd> </Dl> </Li> <Dl> <Dd> It should be difficult to find two different messages m and m such that hash (m) = hash (m). Such a pair is called a cryptographic hash collision . This property is sometimes referred to as strong collision resistance . It requires a hash value at least twice as long as that required for pre-image resistance; otherwise collisions may be found by a birthday attack . </Dd> </Dl>

A one-way hash function is also known as a fingerprint