  This paper studies leakage of user passwords and PINs based on observations
of typing feedback on screens or from projectors in the form of masked
characters that indicate keystrokes. To this end, we developed an attack called
Password and Pin Information Leakage from Obfuscated Typing Videos (PILOT). Our
attack extracts inter-keystroke timing information from videos of password
masking characters displayed when users type their password on a computer, or
their PIN at an ATM. We conducted several experiments in various attack
scenarios. Results indicate that, while in some cases leakage is minor, it is
quite substantial in others. By leveraging inter-keystroke timings, PILOT
recovers 8-character alphanumeric passwords in as little as 19 attempts. When
guessing PINs, PILOT significantly improved on both random guessing and the
attack strategy adopted in our prior work [4]. In particular, we were able to
guess about 3% of the PINs within 10 attempts. This corresponds to a 26-fold
improvement compared to random guessing. Our results strongly indicate that
secure password masking GUIs must consider the information leakage identified
in this paper.
