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Hagita Mariko
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Research Keywords 【 display / non-display 】
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Combinatorics, Cryptography, error correcting sequence, coloring, block design
Research Pursuits 【 display / non-display 】
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We propose two stream ciphers based on a non-secure pseudorandom number generator (called the mother generator).
The mother generator is here chosen to be
the Mersenne Twister (MT), a widely used 32-bit integer generator having 19937 bits of internal state and period $2^{19937}-1$.
One proposal is CryptMT, which computes the accumulative product of the output of MT, and use the most significant 8 bits as a secure random numbers. Its period is proved to be $2^{19937}-1$, and it is 1.5-2.0 times faster than the most optimized AES in counter-mode.
The other proposal, named Fubuki, is designed to be usable also as a block cipher.
It prepares nine different kinds of encryption functions (bijections from blocks to blocks),
each of which takes a parameter.
Fubuki encrypts a sequence of blocks (= a plain message) by applying these encryption functions iteratedly to each of the blocks. Both the combination of the functions and their parameters are pseudorandomly chosen by using its mother generator MT. The key and the initial value are passed to the initialization scheme of MT.
Academic 【 display / non-display 】
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慶應義塾大学大学院, 理工学研究科, 数理科学専攻, 大学院（博士課程）, 修了, Japan
Campus Career 【 display / non-display 】
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Faculty of Core Research Natural Sciences Division, Professor, 2018.04 -
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Graduate School of Humanities and Sciences, Education Organization, Doctral Program Advanced Sciences, 2015.04 -
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Graduate School of Humanities and Sciences, Education Organization, Master's Program Advanced Sciences, 2015.04 -
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Faculty of Science Information Sciences, 2012.04 -
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Faculty of Core Research Natural Sciences Division, Associate Professor, 2015.04 - 2018.03
Books 【 display / non-display 】
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ヴァン・リント＆ウィルソン 組合せ論 下
第21章 強正則グラフと偏均衡幾何， 第22章 直交ラテン方格， 第27章 差集合と自己同型写像， 第28章 差集合と群環， 第29章 符号と対称デザイン, A Course in Combinatorics, Second edition, 丸善出版, Cambridge University Press, 2019.10, 2001, 神保雅一・澤正憲・萩田真理子, J.H.van Lint, R.M.Wilson, Scholarly book, 1-46, 119-158
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ヴァン・リント＆ウィルソン 組合せ論 上
符号とデザイン, A Course in Combinatorics, Second edition, 丸善出版, Cambridge University Press, 2018.03, 2001, 神保雅一・澤正憲・萩田真理子, J.H.van Lint, R.M.Wilson, Scholarly book, 275-293
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Introduction to algebra for cryptography
2010.12, Mariko Hagita, Textbook, survey, introduction
Papers 【 display / non-display 】
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Projective de Bruijn Sequences
Lecture notes in Computer Science, , 2008.09, Yuki Ohtsuka, Makoto Matsumoto, Mariko Hagita, Original, Research paper (scientific journal), Coauthor
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Errot Correcting Sequence and Projective DeBruijn Graph
Graphs and Combinatorics, , 2008.06, Mariko Hagita, Makoto Matsumoto, Fumio Natsu Yuki Ohtsuka, Original, Research paper (scientific journal), Capital Author
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Cryptanalysis of CryptMT: Effect of Huge Prime Period and Multiplicative Filter
{eSTREAM}, {ECRYPT} Stream Cipher Project, , 2005, Makoto Matsumoto, Mutsuo Saito, Takuji Nishimura and Mariko Hagita, Coauthor
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Mersenne Twister and Fubuki Stream/Block Cipher
{eSTREAM}, {ECRYPT} Stream Cipher Project, , 2005, Makoto Matsumoto, Hagita Mariko, Takuji Nishimura and Mutsuo Saito, Original, Coauthor
Published Article 【 display / non-display 】
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書評 パズルでめぐる奇妙な数学ワールド イアン・スチュアート著，伊藤文英訳
数学通信, 2007, 萩田真理子, Single Author
Presentations 【 display / non-display 】
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1 and 2-error correcting sequence
Mariko Hagita, Domestic, 2013.06, , Workshop for Quasi-Monte Carlo and Pseudo Random Number Generation, Invited, Main Speaker
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擬似乱数の評価方法の検証
Ayana Takahashi, Mariko Hagita, Domestic, 2013.03, , 日本応用数理学会研究部会連合発表会, 東洋大学白山キャンパス, Not Invited, Coauthor
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グラフの彩色多項式
Arisa Nakada, Mariko Hagita, Domestic, 2013.03, , 日本応用数理学会研究部会連合発表会, 東洋大学白山キャンパス, Not Invited, Coauthor
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GF(2)上の2-誤り訂正符号系列の存在条件
Mariko Hagita, Makoto Matsumoto, Domestic, 2012.12, , 応用数学合同研究集会, Not Invited, Main Speaker
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2-誤り訂正符号系列の存在条件
Mariko Hagita, Domestic, 2012.03, , 関西グラフ理論研究集会, Not Invited, Main Speaker
Receipt of outside funds (Education, Research, Contribution to Society and industry-academia[government] collaboration) 【 display / non-display 】
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Grant-in-Aid for Scientific Research(C)2023, 700,000Thousand yen
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Grant-in-Aid for Scientific Research(C)2022, 900,000Thousand yen
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Grant-in-Aid for Scientific Research(C)2021, 900,000Thousand yen
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Grant-in-Aid for Scientific Research(C)2020, 900,000Thousand yen
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Grant-in-Aid for Early-Career Scientists2013, 1,000,000Thousand yen
Contributions as an officer, member, etc., of an academic society 【 display / non-display 】
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2015.04 - now，Committee Member, Domestic
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2015.04 - now，Committee Member, 0972-8600, International
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2014.04 - 2015.03，Committee Member, 0972-8600, International
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2014.04 - 2015.03，Committee Member, Domestic
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2014.04 - 2015.03，Committee Member, Domestic
Open lectures; lectures, courses, and seminars; guest lectures; etc. 【 display / non-display 】
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女子中高生夏の学校2009 暗号を作ろう
2009.08, 国立女性教育会館
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平成１８年度 広島大学公開講座 数学の基礎と展望 －調べる・わかる・創り出す－ 並列計算機によるシミュレーションと、地図の塗り分け問題
2006.08, 主催 広島大学理学部数学教室 共催 広島大学総合科学部数学教室 後援 広島県教育委員会
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一学年、並びに二、三学年理系特別数学講義
2004.07, 新潟県立新潟南高等学校
Media coverage, appearances, commentary, etc. 【 display / non-display 】
- エレガントな解答を求む 解答 数学セミナー
2011.09.01, 日本評論社
- エレガントな解答を求む 数学セミナー
2011.05.01, 日本評論社
- エレガントな解答を求む 解答 数学セミナー
2010.08.01, 日本評論社
- エレガントな解答を求む 数学セミナー
2010.05.01, 日本評論社
- エレガントな解答を求む 解答 数学セミナー
2009.07.01, 日本評論社