Topics of Mathematics in Cryptology Probability Theory

A probability is an indicator how likely something is to happen. For example, if we roll probability a die, we may ask what the probability is that we roll a six. In other words, there is a certain event A := “we roll a six”, and we ask for the probability Pr[A] that this event event occurs. In our example, for a fair die, Pr[A] = 16 because there are six equally likely numbers we can roll. So, an event is a description of something that may or may not happen, and the probability of that event tells us how often it happens. (E.g., if Pr[A] = 1/n, then A happens one out of n times.) From this intuitive description, we can easily see the following basic laws of probability: