Toshiyuki Isshiki

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We discuss the merits of using group signature technology in Identity Management. We propose a novel model of group signature scheme and introduce a new entity called User-Revocation manager. User-Revocation manager plays an independent role regarding user revocation which was previously covered by either Group manager or Issuing manager. We extend the idea(More)
Group signature is one of the main theme in recent digital signature studies. Typical signature algorithm is a combination of more than 70 elliptic curve (ECC), modular (RSA), long-bit integer and hash arithmetic functions. A full H/W IP core is strongly desired for the use of group signature in SoCs in slow-clock and low-power mobile devices and embedded(More)
This paper proposes a novel secure biometric authentication scheme that hides the biometric features and the distance between the enrolled and authenticated biometric features, and prevent impersonation. To confirm that the proposed scheme has such properties, we formally model secure biometric authentication schemes by generalizing the related and proposed(More)
We formalize the notion of several weakened random oracle models in order to capture which property of a hash function is crucial to prove the security of a cryptographic scheme. In particular, we focus on augmenting the random oracle with additional oracles that respectively return collisions, secondpreimages, and first-preimages. We study the security of(More)
A sanitizable signature scheme is a signature scheme that allows the sanitizer to sanitize certain portions of the document and to generate the valid signature of the resulting document with no interaction with the signer. There exist many models and schemes for sanitizable signature. In this paper, we precisely formalize the algorithms and the security(More)
Natural (molybdenite) and synthesized molybdenum disulfide crystals have been studied by high-resolution transmission electron microscopy. The image simulation demonstrates that the [0001] and [0110] HRTEM images of hexagonal and rhombohedral MoS2 crystals hardly disclose their stacking sequences, and that the [2110] images can distinguish the Mo and S(More)