Optical path length

In telecommunication, a password length parameter is a basic parameter the value of which affects password strength against brute force attack and so is a contributor to computer security.

One use of the password length parameters is in the expression $P=L\times R/S$, 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 into 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').

The degree of password security is determined by the probability that a password can be guessed in its lifetime.