Research Keywords 【 display / non-display

  • Combinatorics, Cryptography, error correcting sequence, coloring, block design

Research Pursuits 【 display / non-display

  • 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.

Campus Career 【 display / non-display

  • Graduate School of Humanities and Sciences, Research Organization, the Core Section The Natural/Applied Sciences Division, Associate Professor

  • Faculty of Core Research Natural Science Division, Associate Professor

  • Graduate School of Humanities and Sciences, Education Organization, Doctral Program Advanced Sciences

  • Graduate School of Humanities and Sciences, Education Organization, Doctral Program Advanced Sciences

  • Graduate School of Humanities and Sciences, Education Organization, Master's Program Advanced Sciences

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Books 【 display / non-display

  • Introduction to algebra for cryptography

    2010.12, Mariko Hagita, Textbook

Papers 【 display / non-display

  • Projective de Bruijn Sequences

    Lecture notes in Computer Science, 2008.09, Yuki Ohtsuka, Makoto Matsumoto, Mariko Hagita, Original, Research paper (scientific journal), Coauthor

  • 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

  • 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

  • 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

  • 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

  • 1 and 2-error correcting sequence

    Mariko Hagita, Domestic, 2013.06, Workshop for Quasi-Monte Carlo and Pseudo Random Number Generation, Invited, Main Speaker

  • 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

  • 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

  • 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

  • 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

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Industrial Property 【 display / non-display

  • 暗号鍵更新方法

    萩田 真理子, 学校法人 慶應義塾