IllusionPIN demonstration

IllusionPIN: Shoulder-Surfing Resistant Authentication Using Hybrid Images

We address the problem of shoulder-surfing attacks on authentication schemes by proposing IllusionPIN (IPIN), a PIN-based authentication method that operates on touchscreen devices. IPIN uses the technique of hybrid images to blend two keypads with different digit orderings in such a way, that the user who is close to the device is seeing one keypad to enter her PIN, while the attacker who is looking at the device from a bigger distance is seeing only the other keypad. The user’s keypad is shuffled in every authentication attempt since the attacker may memorize the spatial arrangement of the pressed digits.

To reason about the security of IllusionPIN, we developed an algorithm which is based on human visual perception and estimates the minimum distance from which an observer is unable to interpret the keypad of the user. We tested our estimations with 84 simulated shoulder-surfing attacks from 21 different people. None of the attacks was successful against our estimations. In addition, we estimated the minimum distance from which a camera is unable to capture the visual information from the keypad of the user. Based on our analysis, it seems practically almost impossible for a surveillance camera to capture the PIN of a smartphone user when IPIN is in use.


  1. Athanasios Papadopoulos, Toan Nguyen, Emre Durmus, Nasir Memon, IllusionPIN: Shoulder-Surfing Resistant Authentication Using Hybrid Images, IEEE Transactions on Information Forensics and Security (TIFS), Volume 12, Issue 12, December 2017, Pages 2875-2889


  1. Tricking the eye to defeat shoulder-surfing attacks, NYU Press Release
  2. The optical illusion that could protect your passcodes: Researchers reveal keypad that looks different if someone looks over your shoulder, Daily Mail
  3. The 5 Coolest Things On Earth This Week - GE Reports -
  4. This smartphone optical illusion could stop thieves from stealing your PIN or passcode, IBTimes
  5. Clever illusion helps protect your PIN from ‘shoulder surfers’, Digital Trends
  6. NYU Tandon’s IllusionPIN Combats Shoulder-Surfing, Washington Square News
  7. More…