1) A system allows the user to choose a password with a strict length of eight characters (not less or more). Assume that 10,000 passwords can be tested per second. The system administrators want to expire passwords once they have a probability of 0.10 of having been guessed. Determine the expected time to meet the probability under each of the following conditions.

a) Password characters maybe be any ASCII character from 1 to 127, inclusive.

b) Password characters may be any alphanumeric characters ("A" through "Z", "a" through "z" and "0" through "9").

c) Passwords characters must be digits.

2) If a salt is added to the passwords in each of the cases above, would the probability of guessing the password increase or decrease? Why?