The collision resistance property requires that two different input messages should not hash to the same output. In other words, h(x) != h(z). This property is also known as strong collision resistance.
All these properties are shown in the following diagram:
Three security properties of hash functions
Due to their very nature, hash functions will always have some collisions. This is where two different messages hash to the same output. However, they should be computationally impractical to find. A concept known as the avalanche effect is desirable in all hash functions. The avalanche effect specifies that a small change, ...
