A Secure and Practical Sample-then-lock Scheme for Iris Recognition

• Main Authors: Zhu, Feng, Shen, Peisong, Chen, Kaini, Ma, Yucheng, Chen, Chi
• Format: Conference Proceeding
• Language: English
• Subjects: Codes; Cryptography; Entropy; Force; Pattern recognition; Resists; Stability analysis
• ISSN: 2831-7475
• DOI: 10.1109/ICPR56361.2022.9956077

Sample-then-lock construction is a reusable fuzzy extractor for low-entropy sources. When applied on iris recognition scenarios, many subsets of an iris-code are used to lock the cryptographic key. The security of this construction relies on the entropy of subsets of iris codes. Simhadri et al. reported a security level of 32 bits on iris sources. In this paper, we propose two kinds of attacks to crack existing sample-then-lock schemes. Exploiting the low-entropy subsets, our attacks can break the locked key and the enrollment iris-code respectively in less than 2 20 brute force attempts. To protect from these proposed attacks, we design an improved sample-then-lock scheme. More precisely, our scheme employs stability and discriminability to select high-entropy subsets to lock the genuine secret, and conceals genuine locker by a large amount of chaff lockers. Our experiment verifies that existing schemes are vulnerable to the proposed attacks with a security level of less than 20 bits, while our scheme can resist these attacks with a security level of more than 100 bits when number of genuine subsets is 10 6 .