Hand Me Your PIN! Inferring ATM PINs of Users Typing with a Covered Hand

Hand Me Your PIN! Inferring ATM PINs of Users Typing with a Covered Hand

Cardaioli, Matteo (Università degli Studi di Padova; GFT, Milan)
Cecconello, S. (Università degli Studi di Padova)
Conti, M. (Università degli Studi di Padova)
Milani, Simone (Università degli Studi di Padova)
Picek, S. (TU Delft Cyber Security)
Saraci, Eugen (Università degli Studi di Padova)

2022

Automated Teller Machines (ATMs) represent the most used system for withdrawing cash. The European Central Bank reported more than 11 billion cash withdrawals and loading/unloading transactions on the European ATMs in 2019. Although ATMs have undergone various technological evolutions, Personal Identification Numbers (PINs) are still the most common authentication method for these devices. Unfortunately, the PIN mechanism is vulnerable to shoulder-surfing attacks performed via hidden cameras installed near the ATM to catch the PIN pad. To overcome this problem, people get used to covering the typing hand with the other hand. While such users probably believe this behavior is safe enough to protect against mentioned attacks, there is no clear assessment of this countermeasure in the scientific literature. This paper proposes a novel attack to reconstruct PINs entered by victims covering the typing hand with the other hand. We consider the setting where the attacker can access an ATM PIN pad of the same brand/model as the target one. Afterward, the attacker uses that model to infer the digits pressed by the victim while entering the PIN. Our attack owes its success to a carefully selected deep learning architecture that can infer the PIN from the typing hand position and movements. We run a detailed experimental analysis including 58 users. With our approach, we can guess 30% of the 5-digit PINs within three attempts - the ones usually allowed by ATM before blocking the card. We also conducted a survey with 78 users that managed to reach an accuracy of only 7.92% on average for the same setting. Finally, we evaluate a shielding countermeasure that proved to be rather inefficient unless the whole keypad is shielded.

http://resolver.tudelft.nl/uuid:75683830-79eb-44b6-8a9e-1fe87d1e2b95

USENIX Association

9781939133311

Proceedings of the 31st USENIX Security Symposium, Security 2022

31st USENIX Security Symposium, Security 2022, 2022-08-10 → 2022-08-12, Boston, United States

Proceedings of the 31st USENIX Security Symposium, Security 2022

Institutional Repository

conference paper

© 2022 Matteo Cardaioli, S. Cecconello, M. Conti, Simone Milani, S. Picek, Eugen Saraci