The question of how best to perform user authentication is a puzzle that is quite tough to solve. While newer techniques keep emerging, the bread-and-butter user authentication technology of passwords will not go away very soon. Usage of passwords for authenticating users raises several concerns, such as how long the passwords should be, using what combinations of letters, digits, special symbols, etc; and also how long should passwords remain valid (i.e. how frequently they should expire), and so on.