Say a hacker has a list of ndistinct password candidates, only one of which will successfully log her into a secure system.
a.If she tries passwords from the list at random, deleting those passwords that do not work, what is the probability that her first successful login will be (exactly) on her k-th try?
b.Now say the hacker tries passwords from the list at random, but does notdelete previously tried passwords from the list. She stops after her first successful login attempt. What is the probability that her first successful login will be (exactly) on her k-th try?