Though storing in Array takes O(1) time, searching in it takes at least O(log n) time. This time appears to be small, but for a large data set, it can cause a lot of problems and this, in turn, makes the Array data structure inefficient. If H(A) is the hash and H() is the hash function, A will be the pre-image. So, the pre-image resistance states that if given H(A), it is infeasible to figure out the value of A. Let’s look at some of the unique properties and features of these hash functions. Hash functions are