A basic parameter affecting the password length needed to provide a given degree of security. Note 1: Password length parameters are related by the expression P = LR/S, where P is the probability that a password can be guessed in its lifetime, L is the maximum lifetime a password can be used to log in to a system, R is the number of guesses per unit of time, and S is the number of unique algorithm-generated passwords (the password space. ) Note 2: The degree of password security is determined by the probability that a password can be guessed in its lifetime.