With the 1 second sleep (for the first attempt) I was thinking of something along the lines of this: t1 = time(); /* Perform login credentials check, if okay

With the 1 second sleep (for the first attempt) I was thinking of something along the lines of this: t1 = time(); /* Perform login credentials check, if okay return */ loginattempt = n; sleep(n^2 - time() + t1); In other words, the sleep time includes the time it took to process the login info.