Faculty Profiles - NOGAMI Yasuyuki

Papers - NOGAMI Yasuyuki

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Consideration for Affects of an XOR in a Random Number Generator Using Ring Oscillators.

Ryoichi Sato, Yuta Kodera, Ali Md. Arshad, Takuya Kusaka, Yasuyuki Nogami, Robert H. Morelos-Zaragoza

Entropy 23 ( 9 ) 1168 - 1168 2021

Language：English Publishing type：Research paper (scientific journal) Publisher：MDPI

A cloud service to offer entropy has been paid much attention to. As one of the entropy sources, a physical random number generator is used as a true random number generator, relying on its irreproducibility. This paper focuses on a physical random number generator using a field-programmable gate array as an entropy source by employing ring oscillator circuits as a representative true random number generator. This paper investigates the effects of an XOR gate in the oscillation circuit by observing the output signal period. It aims to reveal the relationship between inputs and the output through the XOR gate in the target generator. The authors conduct two experiments to consider the relevance. It is confirmed that combining two ring oscillators with an XOR gate increases the complexity of the output cycle. In addition, verification using state transitions showed that the probability of the state transitions was evenly distributed by increasing the number of ring oscillator circuits.

DOI： 10.3390/e23091168

Web of Science

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Improvement of Final Exponentiation for Pairings on BLS Curves with Embedding Degree 15

NANJO Yuki, SHIRASE Masaaki, KUSAKA Takuya, NOGAMI Yasuyuki

IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences 104 ( 1 ) 315 - 318 2021

Language：English Publishing type：Research paper (scientific journal) Publisher：The Institute of Electronics, Information and Communication Engineers

<p>To be suitable in practice, pairings are typically carried out by two steps, which consist of the Miller loop and final exponentiation. To improve the final exponentiation step of a pairing on the BLS family of pairing-friendly elliptic curves with embedding degree 15, the authors provide a new representation of the exponent. The proposal can achieve a more reduction of the calculation cost of the final exponentiation than the previous method by Fouotsa et al.</p>

DOI： 10.1587/transfun.2020EAL2046

Other Link： https://dblp.uni-trier.de/db/journals/ieiceta/ieiceta104.html#NanjoSKN21

Restrictions of Integer Parameters for Generating Attractive BLS Subfamilies of Pairing-Friendly Elliptic Curves with Specific Embedding Degrees

Nanjo Yuki, Shirase Masaaki, Kusaka Takuya, Nogami Yasuyuki

International Journal of Networking and Computing 11 ( 2 ) 383 - 411 2021

Language：English Publishing type：Research paper (scientific journal) Publisher：IJNC Editorial Committee

Pairings are widely used for innovative protocols such as ID-based encryption and group signature authentication. According to the recent works, the Barreto-Lynn-Scott (BLS) family of pairing-friendly elliptic curves is suggested for the pairings at the various security levels. One of the important facts is that the BLS family has fixed polynomial parameters of a field characteristic and group order in terms of an integer x_0. For practical pairing-based protocols, we have to carefully find x_0 which leads to efficient pairings, however, this search of x_0 is typically complicated. Thus, it is desired some convenient ways of finding x_0 which have advantageous for the pairings. For this reason, Costello et al. proposed simple restrictions for finding x_0 that generates the specific BLS subfamilies of curves with embedding degree k = 24 having one of the best field and curve constructions for the pairings. Since there are demands of such restrictions for the other cases of the embedding degrees, the authors extend their work and provide these for the cases of k = 2^m 3 and 3^n with arbitrary integers m, n>0 in this paper. The results will help to find new parameters which lead to one of the best performing pairings with the BLS family of curves with various k. The results also allow us to respond to change in the security levels of the pairings flexibly according to the progress in the security analyses in the future.

DOI： 10.15803/ijnc.11.2_383

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Other Link： https://dblp.uni-trier.de/db/journals/ijnc/ijnc11.html#NanjoSKN21

Sophisticated analysis of a method to eliminate fruitless cycles for Pollard's rho method with skew Frobenius mapping over a Barreto-Naehrig curve

Miura Hiromasa, Kanzawa Syota, Matsumura Rikuya, Kodera Yuta, Kusaka Takuya, Nogami Yasuyuki

International Journal of Networking and Computing 11 ( 2 ) 231 - 250 2021

Language：English Publishing type：Research paper (scientific journal) Publisher：IJNC Editorial Committee

In this paper, the authors focus on and propose an approach to attack a kind of pairing-friendly curves, the Barreto-Naehring (BN) curve, to accelerate the evaluation of the security level concerning the elliptic curve discrete logarithm problem (ECDLP). More precisely, this paper targets the BN curve, which is known to be a pairing-friendly curve, and Pollard's rho method based on the random-walk is adopted to attack the curve.Though Pollard's rho method with skew Frobenius mapping is known to solve the ECDLP efficiently, this approach sometimes induces the unsolvable cycle, called the fruitless cycle, and such trials must restart with a different starting point. However, any effective method to eliminate such fruitless cycles has not been proposed. Therefore, the authors focus and give the sophisticated analysis to propose an effective approach to eliminate such cycles to optimize Pollard's rho method furthermore. In addition, we confirm the effectiveness of the method by applying it to a BN curve with 12, 17, and 33-bit parameters.

DOI： 10.15803/ijnc.11.2_231

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Other Link： https://dblp.uni-trier.de/db/journals/ijnc/ijnc11.html#MiuraKMKKN21

An Optimal Curve Parameters for BLS12 Elliptic Curve Pairing and Its Efficiency Evaluation.

Daichi Hattori, Yuto Takahashi, Tomoya Tatara, Yuki Nanjo, Takuya Kusaka, Yasuyuki Nogami