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- Seigo Arita
- Discrete Applied Mathematics
- 2003

Nowadays, elliptic curve cryptosystems receive attention and much effort is being dedicated to make it more and more practical. It is worthwhile to construct discrete logarithm based cryptosystems using more general algebraic curves, because it supplies more security sources for public key cryptosystems. The presented paper introduces Cab curves. Roughly… (More)

- Seigo Arita
- ASIACRYPT
- 2000

- Seigo Arita, Kazuto Matsuo, Koh-ichi Nagao, Mahoro Shimura
- IEICE Transactions
- 2004

This paper shows that many of elliptic curve cryptosystems over quartic extension fields of odd characteristics are reduced to genus two hyperelliptic curve cryptosystems over quadratic extension fields. Moreover, it shows that almost all of the genus two hyperelliptic curve cryptosystems over quadratic extension fields of odd characteristics come under… (More)

- Seigo Arita
- ANTS
- 2000

This paper proposes a heuristic algorithm which, given a basis of a subspace of the space of cuspforms of weight 2 for Γ0(N) which is invariant for the action of the Hecke operators, tests whether the subspace corresponds to a quotient A of the jacobian of the modular curve X0(N) such that A is the jacobian of a curve C. Moreover, equations for such a curve… (More)

- Hideo Shimazu, Seigo Arita, Yosuke Takashima
- COLING
- 1992

We have designed and experimentally implemented a tool for developing a natural language systems tha t can accept extra-grammatical expressions, keyword sequences, and linguistic fragments, as well as ordi nary na tura l language queries. The key to this tool 's efficiency is its effective use of a simple keyword analyzer in combination with a conventional… (More)

- Seigo Arita
- IEICE Transactions
- 2003

There are three well-known identification schemes: Fiat-Shamir, GQ and Schnorr identification schemes. All of them are proven secure against passive or active attacks under number theoretic assumptions. However, the efficiencies of reductions in those proofs are not tight, since they need “rewinding.” We show an identification scheme IDKEA1. Although it… (More)

- Hideo Shimazu, Seigo Arita, Yosuke Takashima
- COLING
- 1994

This paper describes the first reported grammatical framework for a nmltimodal interface. Although multimodal interfaces offer the promise of a flexible and user fl'iendly means of human-coml)uter interaction, no study has yet appeared on formal granunatical f'l'ame-works for theln. We have developed Multi-Modal Definite Clause Ch'ammar (MM-I)CG), an… (More)

- Seigo Arita
- Public Key Cryptography
- 2000

Gaudry has described a new algorithm (Gaudry’s variant) for the discrete logarithm problem (DLP) in hyperelliptic curves. For a hyperelliptic curve of a small genus on a finite field GF(q), Gaudry’s variant solves for the DLP in time O(q2+2). This paper shows that Cab curves can be attacked with a modified form of Gaudry’s variant and presents the timing… (More)

This paper shows a commitment protocol which under the KEA1 and Revocable DDH assumptions securely realizes the ideal functionality FCOM of a single commitment. We use an extractor in KEA1 assumption in order to realize extractability of the protocol. By the protocol we can commit to k-bit message with O(k) bits in O(k) computations. It is as efficient as… (More)

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