JaLCDOI 10.18926/fest/11479
FullText URL 010_001_007.pdf
Author Wang Xiao Dong| Ishikawa, Hirofumi|
Abstract The one-way hash function plays an important role in digital signatures and message authentication from the viewpoint of security. No effective attacking method has been discovered to the algorithm of hash function standard. In this study, we tried to attack SHA-256 in encryption mode using linear and differential cryptanalysis to solve a private key. We deduced that an estimate of the private key would require huge known and chosen plaintexts in both linear and differential cryptanalysis, and that it would be difficult to decipher SHA-256 in view of the required computation.
Keywords differential cryptanalysis encryption mode hash function linear cryptanalysis SHA-256
Publication Title 岡山大学環境理工学部研究報告
Published Date 2005-02-28
Volume volume10
Issue issue1
Start Page 1
End Page 7
ISSN 1341-9099
language 日本語
File Version publisher
NAID 120002313630
JaLCDOI 10.18926/fest/11449
FullText URL 009_019_026.pdf
Author Sakamura Kenichi| Dong Wang Xiao| Ishikawa, Hirofumi|
Abstract We have investigated the linear cryptanalysis of AES cipher in this article. As the previous encryption standard DES could be broken by the linear cryptanalysis, NIST decided a new encryption standard AES in 2000. We try to analyze one and two rounds AES cipher by the method of the linear cryptanalysis and learn the limits of this mehtod. AES cipher provides a conspicuous difficulty in breaking its keys because of small bias of its S-box. We report the experimental results of success rate and are led to conclusion that this method would not work well on more than 3 rounds to break keys.
Keywords AES Chosen plaintext attack Linear cryptanalysis
Publication Title 岡山大学環境理工学部研究報告
Published Date 2004-02-27
Volume volume9
Issue issue1
Start Page 19
End Page 26
ISSN 1341-9099
language 英語
File Version publisher
NAID 120002313376
JaLCDOI 10.18926/fest/11425
Title Alternative A mathematical model of Plasmodium falciparum transmission incorporating drug resistance: Simulations of the Solomon Islands situation
FullText URL 012_019_027.pdf
Author Chen, Tiantian| Nishina, Tomohiko| Hisakane, Naoto| Ishikawa, Hirofumi|
Abstract The Solomon Islands are known as a high endemic region of malaria. The resistance of Plasmodium falciparum to chloroquine has been confirmed since 1980 in the Solomon Islands, and the spread of chloroquine resistance is a big hurdle to malaria control. We have constructured the model for P. falciparum making allowance of chloroquine resistance. We distinguish the infection of resistance strains from that of sensitive strains in both the human and the vector populations. Since the overall parasite rate and the parasite rate of gametocytes for P. falciparum are strongly dependent on age, the human population is divided into 7 age groups in the model. The epidemiological parameters are determined by malariological survey in northeastern Guadalcanal (Ishii et al.) and the sporozoite rate in vector population is assumed as 0.1% based on the entomological study (Harada et al.) Our study aims at estimating the effect of mass drug administration under the presence of drug-resistance and also analyzing the escalation of drug-resistance through the transmission model for P. falciparum which can deal with chloroquine resistance.
Keywords Solomon Islands Plasmodium falciparum drug resistance model
Publication Title 岡山大学環境理工学部研究報告
Published Date 2007-03-15
Volume volume12
Issue issue1
Start Page 19
End Page 27
ISSN 1341-9099
language 日本語
File Version publisher
NAID 120002313858
JaLCDOI 10.18926/fest/11424
FullText URL 011_009_014.pdf
Author Nishina Tomohiko| Tian Tian Chen| Fujita Kazutoshi| Ishikawa, Hirofumi|
Abstract The red fox (Vulpes vulepes) and the vole ( Clethrionomys refocanus) are principal hosts of Echinococcus multilocularis in Hokkaido, Japan. How protoscoleces increases in voles and the level of immunity in foxes remain unknown because of the lack of survey data, so that it is important to clarify these mecahnisms in order to develop control strategies against E. multilocularis. In this study, the growth of protoscoleces in the infected voles was approximated as the logistic curve, the level of immunity in the fox was assumed to depend on the experience of the infection with E. multilocularis, and the worm burden in the fox was assumed to be governed by the amount of protoscoleces in the vole. Our model showed that the population densities of the hosts and the level of immunity influenced the prevalence of the E. multilocularis.
Keywords Echinococcus multilocularis protoscoleces immunity worm burden stochastic model
Publication Title 岡山大学環境理工学部研究報告
Published Date 2006-03-15
Volume volume11
Issue issue1
Start Page 9
End Page 14
ISSN 1341-9099
language 英語
File Version publisher
NAID 120002314034
JaLCDOI 10.18926/fest/11423
FullText URL 012_007_018.pdf
Author Imura Keigo| XiaoDong Wang| Ishikawa, Hirofumi|
Abstract The elliptic curve cryptosystem is a popular cryptosystem. Its safety depends on the difficulty of the elliptic curve discrete logarithm problem (ECDLP). From the viewpoint of ECDLP, it is very interesting to determine the order of elliptic curves. We tabulate the order of elliptic curves on the finite field of characteristic two using the Schoof algorithm, which is an efficient algorithm to decide orders. The Schoof algorithm is carried out by O(log(8)q). Because the calculation of y(q2) occupies most of the time used to execute the Schoof algorithm, it is necessary to reduce the amount of y(q2) calculations.
Keywords elliptic curve order division polynomial Schoof algorithm finite field of characteristic two
Publication Title 岡山大学環境理工学部研究報告
Published Date 2007-03-15
Volume volume12
Issue issue1
Start Page 7
End Page 18
ISSN 1341-9099
language 英語
File Version publisher
NAID 120002313838
JaLCDOI 10.18926/fest/11422
FullText URL 011_001_007.pdf
Author Fujita Kazutoshi| Tian Tian Chen| Nishina Tomohiko| Ishikawa, Hirofumi|
Abstract Plasmodium vivax re-emerged in 1993 near the demilitarized zone (DMZ) in South Korea, although P. vivax malaria disappeared in South Korea in 1979. The re-emergence of malaria in South Korea is believed to have originated from infection by mosquitoes from North Korea across the DMZ. The principal vector of P. vivax in the Korean Peninsula is Anopheles sinensis. The density of An. sinensis has a peak during the second week of July. The North Korean strain of P. vivax has 2 characteristics: a wide distribution of the terms of relapse and a high rate of relapse. Therefore, we may well wonder why the incidence of malaria is concentrated in summer, especially in August. Mathematical models in North Korea and South Korea were constructed in which the South Korean model was affected unidirectionally by the North Korean model. We carried out simulations of the model for the Paju-shi and Yonchon-gun situations near the DMZ region. The simulation results followed the time-course of the re-emergence of P. vivax there, and revealed the mechanism of the elevation of the incidence of P. vivax in summer.
Keywords DMZ Korea model Plasmodium vivax re-emergence
Publication Title 岡山大学環境理工学部研究報告
Published Date 2006-03-15
Volume volume11
Issue issue1
Start Page 1
End Page 7
ISSN 1341-9099
language 英語
File Version publisher
NAID 40007297549