Auflistung nach Autor:in "Ohki, Tetsushi"
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- KonferenzbeitragEvaluation of security for biometric guessing attacks in biometric cryptosystem using fuzzy commitment scheme(BIOSIG 2012, 2012) Hidano, Seira; Ohki, Tetsushi; Takahashi, KentaBiometric authentication based on template protection has attracted attention in the past decade. In the discussion on the security of these systems, however, the content of biometric information is assumed to be sufficiently large, and real conditions of biometric features have not yet been reflected. This paper focuses on a biometric cryptosystem using a fuzzy commitment scheme and demonstrates correlation between fingerprint bit strings by using our method for evaluating the content of biometric information. Additionally, attacks to guess biometric bit strings, which take advantage of correlation between them, are explained, and the security against these attacks is theoretically and experimentally discussed.
- KonferenzbeitragImproved Post-quantum-secure Face Template Protection System Based on Packed Homomorphic Encryption(BIOSIG 2021 - Proceedings of the 20th International Conference of the Biometrics Special Interest Group, 2021) Tamiya, Hiroto; Isshiki, Toshiyuki; Mori, Kengo; Obana, Satoshi; Ohki, TetsushiThis paper proposes an efficient face template protection system based on homomorphic encryption. By developing a message packing method suitable for the calculation of the square Euclidean distance, the proposed system computes the squared Euclidean distance between facial features by a single homomorphic multiplication. Our experimental results show the transaction time of the proposed system is about 14 times faster than that of the existing face template protection system based on homomorphic encryption presented in BIOSIG2020.
- KonferenzbeitragNew security definitions for biometric authentication with template protection: toward covering more threats against authentication systems(BIOSIG 2013, 2013) Isshiki, Toshiyuki; Araki, Toshinori; Mori, Kengo; Obana, Satoshi; Ohki, Tetsushi; Sakamoto, ShizuoExisting studies on the security of biometric authentication with template protection have considered the adversaries who obtain only protected templates. Since biometric authentication systems transmit data other than the protected templates, we need to consider how to secure biometric authentication systems against adversaries with those data. In this paper, we propose a classification of adversaries in biometric authentication with template protection into the following three types in accordance with their knowledge: (1) protected template data, (2) data transmitted during authentication, and (3) both types of data. We also propose a new security metric unforgeability, which provides authentication security against attacks by adversaries impersonating someone else on authentication systems even when they cannot obtain the biometric information of a claimant. We then give security definitions against each type of adversary we classified. We also propose a biometric authentication scheme with template protection that is irreversible against all types of adversaries.