Two-Stage Human Verification using HandCAPTCHA and Anti-Spoofed Finger Biometrics with Feature Selection

TL;DR

This paper introduces a two-stage human verification system combining a hand-based CAPTCHA and biometric fingerprint verification with presentation attack detection, achieving high accuracy and security against spoofing and automated attacks.

Contribution

The paper proposes a novel two-stage verification scheme integrating HandCAPTCHA and anti-spoofed fingerprint biometrics with feature selection, enhancing security and accuracy.

Findings

HandCAPTCHA accuracy of 98.5% with 1.23% bot acceptance rate

Zero error rate in presentation attack detection on 255 subjects

Fingerprint identification accuracy of 98% with 6.5% EER

Abstract

This paper presents a human verification scheme in two independent stages to overcome the vulnerabilities of attacks and to enhance security. At the first stage, a hand image-based CAPTCHA (HandCAPTCHA) is tested to avert automated bot-attacks on the subsequent biometric stage. In the next stage, finger biometric verification of a legitimate user is performed with presentation attack detection (PAD) using the real hand images of the person who has passed a random HandCAPTCHA challenge. The electronic screen-based PAD is tested using image quality metrics. After this spoofing detection, geometric features are extracted from the four fingers (excluding the thumb) of real users. A modified forward-backward (M-FoBa) algorithm is devised to select relevant features for biometric authentication. The experiments are performed on the Bogazici University (BU) and the IIT-Delhi (IITD) hand databases using the k-nearest neighbor and random forest classifiers. The average accuracy of the correct HandCAPTCHA solution is 98.5%, and the false accept rate of a bot is 1.23%. The PAD is tested on 255 subjects of BU, and the best average error is 0%. The finger biometric identification accuracy of 98% and an equal error rate (EER) of 6.5% have been achieved for 500 subjects of the BU. For 200 subjects of the IITD, 99.5% identification accuracy, and 5.18% EER are obtained.