研究者業績

澁谷 智治

Shibuya Tomoharu

基本情報

所属
上智大学 理工学部情報理工学科 教授
(兼任)理工学部長
学位
博士(工学)(1999年4月 東京工業大学)

研究者番号
20262280
J-GLOBAL ID
200901097688266540
researchmap会員ID
1000181747

外部リンク

主に以下のような研究を行っています。

・安心・安全な分散コンピューティングに関する研究

・無限個のシェアを生成可能な秘密分散法に関する研究

・各種暗号方式・情報セキュリティに関する研究


論文

 63
  • 信学技報 122(427) 325-330 2023年3月  最終著者責任著者
  • Mariko FUJII, Tomoharu SHIBUYA
    IEICE TRANSACTIONS on Information and Systems E.103-D(1) 11-24 2020年1月1日  査読有り
  • Tomoharu Shibuya, Takeru Sudo
    IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences E100A(12) 2558-2571 2017年12月1日  査読有り
    In this paper, we propose a group theoretic representation suitable for the rank-modulation (RM) scheme over the multi-cell ranking presented by En Gad et al. By introducing an action of the group of all permutation matrices on the set of all permutations, the scheme is clearly reformulated. Moreover, weintroduce the concept ofr-dominating sets over the multi-cell ranking, which is a generalization of conventional dominating sets, inthe design of rank-modulation rewriting codes. The concept together with the proposed group theoretic representation yields an explicit formula of an upper bound on the size of the set of messages that can be stored in the memory by using RM rewriting codes over multi-cell ranking. This bound enables us to consider the trade-off between the size of the storable message set and the rewriting cost more closely. We also provide a concrete example of RM rewriting code that is not available by conventional approaches and whose size of the storable message set can not be achieved by conventional codes.
  • Tomoharu Shibuya, Takeru Sudo
    PROCEEDINGS OF 2016 INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY AND ITS APPLICATIONS (ISITA 2016) 131-135 2016年  
    In this paper, we study rank-modulation (RM) rewriting codes based on dominating sets. By introducing a special class of dominating sets in a construction of RM rewriting codes and employing the notion of a group action in an analysis of those codes, we succeeded to construct. RM rewriting codes based on the dominating sets that maximize the amount of stored data under the limit of rewriting cost for flash memories with 4 and 5 cells.
  • Keisuke Kodaira, Mihoko Wada, Tomoharu Shibuya
    IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES E97A(11) 2247-2253 2014年11月  査読有り
    The amplitude damping (AD) quantum channel is one of the models describing evolution of quantum states. The construction of quantum error correcting codes for the AD channel based on classical codes has been presented, and Shor et al. proposed a class of classical codes over F-3 which are efficiently applicable to this construction. In this study, we expand Shor's construction to that over F-7, and succeeded to construct an AD code that has better parameters than AD codes constructed by Shor et al.

MISC

 44
  • 須藤 尊, 渋谷 智治
    電子情報通信学会技術研究報告 = IEICE technical report : 信学技報 116(395) 231-236 2017年1月19日  
  • Shibuya Tomoharu, Sudo Takeru
    電子情報通信学会技術研究報告 = IEICE technical report : 信学技報 116(33) 115-120 2016年5月19日  
  • Shibuya Tomoharu, Sudo Takeru
    電子情報通信学会技術研究報告 = IEICE technical report : 信学技報 116(34) 115-120 2016年5月19日  
  • 神林 雄也, 渋谷 智治
    電子情報通信学会技術研究報告 : 信学技報 112(461) 113-118 2013年3月7日  
    Rank Modulation符号は,フラッシュメモリを構成する各セルの電荷量の大小関係のみを用いて情報を表現する記録符号である.また,Compressed Encoding,はpush up操作を行うことによってメモリの状態遷移を実現するRnak Modulation符号化の一種である.本研究では,Compressed Encodingにおいて記憶容量増大とブロック消去の発生頻度低減を実現する1手法として知られる,遷移グラフの支配集合に基づく符号構成について検討した.この結果,支配集合を構成する新たなアルゴリズムを提案し,さらに,このアルゴリズムが極小支配集合を生成するための十分条件について明らかにしている.また,メモリを構成するセル数が5のときの,極小支配集合を具体的に構成している.
  • Ihara Hiroyuki, Shibuya Tomoharu
    電子情報通信学会技術研究報告. IT, 情報理論 112(124) 85-89 2012年7月12日  
    Spatially coupled (SC) low-density parity-check (LDPC) codes are denned by bipartite graphs that are obtained by assembling prototype graphs. The combination and connection of prototype graphs are designated by specifying some parameters, and Kudekar et al. showed that BP threshold of the ensemble of SC LDPC codes agrees with MAP threshold of the ensemble of regular LDPC codes when those parameters are grown up so that the code length tends to infinity. When we design SC LDPC codes with practical code length, however, it is not clear how to set those parameters to enhance the performance of SC LDPC codes. In this paper, we provide the result of numerical experiments that suggest the dependence of error performance of SC LDPC codes over BEC on their design parameters.

書籍等出版物

 6

講演・口頭発表等

 14
  • Daisuke Hibino, Tomoharu Shibuya
    Technical Committee Meeting on Information Theory 2023年3月15日
  • Taiyu Kamiyama, Yuta Ugaya, Keisuke Kodaira, Tomoharu Shibuya
    2018 The International Symposium on Information Theory and Its Applications 2018年10月28日 Engineering Sciences Society, IEICE
    conventional secret sharing, password protected secret sharing (PPSS) was invented. Recently, Nakahara et al. improved Ogata's multiple-use PPSS (mPPSS), which protects multiple data by one password, by employing secure computation known as CSEC70 method in the user authentication. In this paper, we propose an attack on Nakahara's mPPSS that presumes on a security hall in the adoption of CSEC70 method. Then, we show that the proposed attack enables an administrator of any server of the system to disclose the password of an arbitrary user in Nakahara's mPPSS.
  • Tomoharu Shibuya
    Japan-Singapore Workshop on Coding and Information Theory 2018年3月4日 School of Physical & Mathematical Sciences, Nanyang Technological University
    In this talk, a group theoretic representation suitable for the rank-modulation (RM) scheme over the multi-cell ranking developed by En Gad et al. is presented. By introducing an action of the group of all permutation matrices on the set of all permutations, the scheme is clearly reformulated. Moreover, we introduce the concept of r-dominating sets over the multi-cell ranking, which is a generalization of conventional dominating sets, in the design of rank-modulation rewriting codes. The concept together with the presented group theoretic representation helps to yield an explicit formula of an upper bound on the size of the set of messages that can be stored in the memory by using RM rewriting codes over multi-cell ranking. We also note that this bound enables us to consider the trade-off between the size of the storable message set and the rewriting cost more closely.
  • 須藤 尊, 渋谷 智治
    電子情報通信学会情報理論研究会 2017年1月20日 電子情報通信学会
  • Tomoharu Shibuya, Takeru Sudo
    Conference of Technical Committee on Information Theory 2016年5月20日 IEICE

共同研究・競争的資金等の研究課題

 13