2022/12/08 更新

写真a

コシバ タケシ
小柴 健史
Scopus 論文情報  
論文数: 0  Citation: 0  h-index: 11

Citation Countは当該年に発表した論文の被引用数

所属
教育・総合科学学術院 教育学部
職名
教授
プロフィール

理論計算機科学全般に関心を持つ。現在の主な興味を挙げると,

  • 暗号理論
    • 一方向性関数や疑似乱数生成器などのプリミティブの諸性質の究明
    • 秘匿計算の構成要素(秘密分散,Secure Message Transmission,紛失通信など)
    • 秘匿計算の応用
    • 合理的敵対者に対する安全性(ゲーム理論と暗号理論の関係)
  • 量子計算・量子暗号・量子情報
    • 量子敵対者に対する暗号プリミティブの安全性
    • ブラインド量子計算
    • 量子学習理論
  • 乱数抽出・疑似乱数生成

となるが,これらに限定している訳ではない。最近の技術的関心は,暗号理論・量子情報・学習理論とも繋がっていることもあり,凸最適化と二乗和最適化にある。

他学部・他研究科等兼任情報

  • 教育・総合科学学術院   大学院教育学研究科

学内研究所・附属機関兼任歴

  • 2021年
    -
    2022年

    データ科学センター   兼任センター員

学歴

  • 1998年04月
    -
    2001年03月

    東京工業大学   大学院情報理工学研究科   数理・計算科学専攻 博士後期課程  

  • 1990年04月
    -
    1992年03月

    東京工業大学   大学院理工学研究科   情報工学専攻 博士前期課程  

  • 1986年04月
    -
    1990年03月

    東京工業大学   工学部   情報工学科  

学位

  • 2001年03月   東京工業大学   博士(理学)

経歴

  • 2017年04月
    -
    継続中

    早稲田大学   教育・総合科学学術院 教育学部 数学科   教授

  • 2015年04月
    -
    2017年03月

    埼玉大学   大学院理工学研究科 情報システム工学科   教授

  • 2005年04月
    -
    2015年03月

    埼玉大学   大学院理工学研究科 情報システム工学科   准教授(助教授)

  • 2010年11月
    -
    2011年02月

    パリ大学7   Laboratoire d'Informatique Algorithmique: Fondements et Applications (LIAFA)   訪問研究員

  • 2010年03月
    -
    2010年11月

    パリ大学11   Laboratoire de Recherche en Informatique (LRI)   訪問研究員

  • 2006年04月
    -
    2009年03月

    統計数理研究所   客員準教授(客員助教授)

  • 1992年04月
    -
    2005年03月

    株式会社富士通研究所   研究員

  • 2002年11月
    -
    2004年09月

    国立研究開発法人科学技術振興機構   ERATO今井量子計算機構プロジェクト   研究員

  • 1999年01月
    -
    2000年03月

    通信・放送機構   情報通信セキュリティプロジェクト   研究員

▼全件表示

所属学協会

  • 2022年02月
    -
     

    日本数学会

  •  
     
     

    情報処理学会

  •  
     
     

    電子情報通信学会

  •  
     
     

    IEEE

  •  
     
     

    ACM

  •  
     
     

    IACR(国際暗号学会)

▼全件表示

 

研究分野

  • 情報学基礎論

研究キーワード

  • 情報セキュリティ

  • 理論計算機科学

  • プライバシー保護

  • 秘匿計算

  • 量子情報

  • 量子計算

  • 暗号理論

▼全件表示

論文

  • Quantum verifiable protocol for secure modulo zero-sum randomness

    Masahito Hayashi, Takeshi Koshiba

    Quantum Information Processing   21 ( 8 ) Article 291 - (42 pages)  2022年08月  [査読有り]  [国際誌]

    担当区分:最終著者

    DOI

    Scopus

  • Bangla-BERT: Transformer-based Efficient Model for Transfer Learning and Language Understanding

    Md Kowsher, Abdullah As Sami, Nusrat Jahan Prottasha, Mohammad Shamsul Arefin, Pranab Kumar Dhar, Takeshi Koshiba

    IEEE Access   10   91855 - 91870  2022年08月  [査読有り]  [国際誌]

    担当区分:責任著者

    DOI

  • AI Makes Crypto Evolve

    Behrouz Zolfaghari, Takeshi Koshiba

    Applied System Innovation   5 ( 4 ) Article 75 - (33 pages)  2022年07月  [査読有り]  [国際誌]  [国際共著]

    担当区分:最終著者

     概要を見る

    The recent literature reveals a dichotomy formed by a coevolution between cryptography and Artificial Intelligence (AI). This dichotomy consists of two sides, namely Crypto-Influenced AI (CIAI) and AI-Influenced Cryptography (AIIC). While it is pertinent to investigate this dichotomy from both sides, the first side has already been studied. In this review, we focused on AIIC. We identified and analyzed the stages on the evolutionary path of AIIC. Moreover, we attempted to anticipate what the future may hold for AIIC given the impact of quantum computing on the present and the future of AI.

    DOI

    Scopus

  • From Random Numbers to Random Objects

    Behrouz Zolfaghari, Khodakhast Bibak, Takeshi Koshiba

    Entropy   24 ( 7 ) Article 928 - (33 pages)  2022年07月  [査読有り]  [国際誌]

    担当区分:最終著者

     概要を見る

    Many security-related scenarios including cryptography depend on the random generation of passwords, permutations, Latin squares, CAPTCHAs and other types of non-numerical entities. Random generation of each entity type is a different problem with different solutions. This study is an attempt at a unified solution for all of the mentioned problems. This paper is the first of its kind to pose, formulate, analyze and solve the problem of random object generation as the general problem of generating random non-numerical entities. We examine solving the problem via connecting it to the well-studied random number generation problem. To this end, we highlight the challenges and propose solutions for each of them. We explain our method using a case study; random Latin square generation.

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • The Dichotomy of Neural Networks and Cryptography: War and Peace

    Behrouz Zolfaghari, Takeshi Koshiba

    Applied System Innovation   5 ( 4 ) Article 61 - (28 pages)  2022年06月  [査読有り]  [国際誌]  [国際共著]

    担当区分:最終著者

     概要を見る

    In recent years, neural networks and cryptographic schemes have come together in war and peace; a cross-impact that forms a dichotomy deserving a comprehensive review study. Neural networks can be used against cryptosystems; they can play roles in cryptanalysis and attacks against encryption algorithms and encrypted data. This side of the dichotomy can be interpreted as a war declared by neural networks. On the other hand, neural networks and cryptographic algorithms can mutually support each other. Neural networks can help improve the performance and the security of cryptosystems, and encryption techniques can support the confidentiality of neural networks. The latter side of the dichotomy can be referred to as the peace. There are, to the best of our knowledge, no current surveys that take a comprehensive look at the many ways neural networks are currently interacting with cryptography. This survey aims to fill that niche by providing an overview on the state of the cross-impact between neural networks and cryptography systems. To this end, this paper will highlight the current areas where progress is being made as well as the aspects where there is room for future research to be conducted.

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • Chaotic Image Encryption: State-of-the-Art, Ecosystem, and Future Roadmap

    Behrouz Zolfaghari, Takeshi Koshiba

    Applied System Innovation   5 ( 3 ) Article 57 - (38 pages)  2022年06月  [査読有り]  [国際誌]  [国際共著]

    担当区分:最終著者

     概要を見る

    Recently, many researchers have been interested in the application of chaos in cryptography. Specifically, numerous research works have been focusing on chaotic image encryption. A comprehensive survey can highlight existing trends and shed light on less-studied topics in the area of chaotic image encryption. In addition to such a survey, this paper studies the main challenges in this field, establishes an ecosystem for chaotic image encryption, and develops a future roadmap for further research in this area.

    DOI

    Scopus

    4
    被引用数
    (Scopus)
  • Perfectly Secure Message Transmission against Rational Adversaries

    Maiki Fujita, Takeshi Koshiba, Kenji Yasunaga

    IEEE Journal of Selected Areas in Information Theory   3 ( 2 ) 390 - 404  2022年06月  [査読有り]  [国際誌]

     概要を見る

    Secure Message Transmission (SMT) is a two-party cryptographic protocol by which the sender can securely and reliably transmit messages to the receiver using multiple channels. An adversary can corrupt a subset of the channels and commit eavesdropping and tampering attacks over the channels. In this work, we introduce a game-theoretic security model for SMT in which adversaries have some preferences for protocol execution. We define rational “timid” adversaries who prefer to violate security requirements but do not prefer the tampering to be detected. First, we consider the basic setting where a single adversary attacks the protocol. We construct perfect SMT protocols against any rational adversary corrupting all but one of the channels. Since minority corruption is required in the traditional setting, our results demonstrate a way of circumventing the cryptographic impossibility results by a game-theoretic approach. Next, we study the setting in which all the channels can be corrupted by multiple adversaries who do not cooperate. Since we cannot hope for any security if a single adversary corrupts all the channels or multiple adversaries cooperate maliciously, the scenario can arise from a game-theoretic model. We also study the scenario in which both malicious and rational adversaries exist.

    DOI

  • Guesswork of a quantum ensemble

    Michele Dall'Arno, Francesco Buscemi, Takeshi Koshiba

    IEEE Transactions on Information Theory   68 ( 5 ) 3139 - 3143  2022年05月  [査読有り]

    担当区分:最終著者

    DOI

  • CARAN: A Context-Aware Recency Based Attention Network for Point-of-interest Recommendation

    Md. Billal Hossain, Mohammad Shamsul Arefin, Iqbal H. Sarker, Md. Kowsher, Pranab Kumar Dhar, Takeshi Koshiba

    IEEE Access   10   36299 - 36310  2022年04月  [査読有り]  [国際誌]  [国際共著]

    担当区分:最終著者

    DOI

  • An Enhanced Neural Word Embedding Model for Transfer Learning

    Md. Kowsher, Md. Shohanur Islam Sobuj, Md. Fahim Shahriar, Nusrat Jahan Prottasha, Mohammad Shamsul Arefin, Pranab Kumar Dhar, Takeshi Koshiba

    Applied Sciences   12 ( 6 ) Article 2848 - (16 pages)  2022年03月  [査読有り]  [国際誌]  [国際共著]

    担当区分:最終著者

     概要を見る

    Due to the expansion of data generation, more and more natural language processing (NLP) tasks are needing to be solved. For this, word representation plays a vital role. Computation-based word embedding in various high languages is very useful. However, until now, low-resource languages such as Bangla have had very limited resources available in terms of models, toolkits, and datasets. Considering this fact, in this paper, an enhanced BanglaFastText word embedding model is developed using Python and two large pre-trained Bangla models of FastText (Skip-gram and cbow). These pre-trained models were trained on a collected large Bangla corpus (around 20 million points of text data, in which every paragraph of text is considered as a data point). BanglaFastText outperformed Facebook’s FastText by a significant margin. To evaluate and analyze the performance of these pre-trained models, the proposed work accomplished text classification based on three popular textual Bangla datasets, and developed models using various machine learning classical approaches, as well as a deep neural network. The evaluations showed a superior performance over existing word embedding techniques and the Facebook Bangla FastText pre-trained model for Bangla NLP. In addition, the performance in the original work concerning these textual datasets provides excellent results. A Python toolkit is proposed, which is convenient for accessing the models and using the models for word embedding, obtaining semantic relationships word-by-word or sentence-by-sentence; sentence embedding for classical machine learning approaches; and also the unsupervised finetuning of any Bangla linguistic dataset.

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • The Odyssey of Entropy: Cryptography

    Behrouz Zolfaghari, Khodakhast Bibak, Takeshi Koshiba

    Entropy   24 ( 2 ) Article 266 - (27 pages)  2022年02月  [査読有り]  [国際誌]  [国際共著]

    担当区分:最終著者

    DOI

    Scopus

    5
    被引用数
    (Scopus)
  • Cryptography in Hierarchical Coded Caching: System Model and Cost Analysis

    Behrouz Zolfaghari, Vikrant Singh, Brijesh Kumar Rai, Khodakhast Bibak, Takeshi Koshiba

    Entropy   23 ( 11 ) Article 1459 - (22 pages)  2021年11月  [査読有り]  [国際誌]  [国際共著]

    担当区分:最終著者

    DOI

    Scopus

    4
    被引用数
    (Scopus)
  • Frequent contiguous pattern mining over biological sequences of protein misfolded diseases

    Mohammad Shahedul Islam, Md. Abul Kashem Mia, Mohammad Shamsur Rahman, Mohammad Shamsul Arefin, Pranab Kumar Dhar, Takeshi Koshiba

    BMC Bioinformatics   22 ( 1 ) Article 435 - (28 pages)  2021年09月  [査読有り]  [国際誌]  [国際共著]

    担当区分:最終著者

     概要を見る

    <title>Abstract</title><sec>
    <title>Background</title>
    Proteins are integral part of all living beings, which are building blocks of many amino acids. To be functionally active, amino acids chain folds up in a complex way to give each protein a unique 3D shape, where a minor error may cause misfolded structure. Genetic disorder diseases i.e. <italic>Alzheimer, Parkinson,</italic> etc. arise due to misfolding in protein sequences. Thus, identifying patterns of amino acids is important for inferring protein associated genetic diseases. Recent studies in predicting amino acids patterns focused on only simple protein misfolded disease i.e. <italic>Chromaffin Tumor</italic>, by association rule mining. However, more complex diseases are yet to be attempted. Moreover, association rules obtained by these studies were not verified by usefulness measuring tools.



    </sec><sec>
    <title>Results</title>
    In this work, we analyzed protein sequences associated with complex protein misfolded diseases (i.e. <italic>Sickle Cell Anemia, Breast Cancer, Cystic Fibrosis, Nephrogenic Diabetes Insipidus,</italic> and <italic>Retinitis Pigmentosa 4</italic>) by association rule mining technique and objective interestingness measuring tools. Experimental results show the effectiveness of our method.


    </sec><sec>
    <title>Conclusion</title>
    Adopting quantitative experimental methods, this work can form more reliable, useful and strong association rules i. e. dominating patterns of amino acid of complex protein misfolded diseases. Thus, in addition to usual applications, the identified patterns can be more useful in discovering medicines for protein misfolded diseases and thereby may open up new opportunities in medical science to handle genetic disorder diseases.


    </sec>

    DOI

    Scopus

  • CricShotClassify: An Approach to Classifying Batting Shots from Cricket Videos Using a Convolutional Neural Network and Gated Recurrent Unit

    Anik Sen, Kaushik Deb, Pranab Kumar Dhar, Takeshi Koshiba

    Sensors   21 ( 8 ) Article 2846 - (19 pages)  2021年04月  [査読有り]  [国際誌]  [国際共著]

    担当区分:最終著者

    DOI

    Scopus

    3
    被引用数
    (Scopus)
  • A Deep Learning Approach to Predict Autism Spectrum Disorder Using Multisite Resting-State fMRI

    Faria Zarin Subah, Kaushik Deb, Pranab Kumar Dhar, Takeshi Koshiba

    Applied Sciences   11 ( 8 ) Article 3636 - (16 pages)  2021年04月  [査読有り]  [国際誌]  [国際共著]

    担当区分:最終著者

    DOI

    Scopus

    11
    被引用数
    (Scopus)
  • Plant Leaf Disease Recognition using Depthwise Separable Convolution Based Models

    Syed Mohammad, Minhaz Hossain, Kaushik Deb, Pranab Kumar Dhar, Takeshi Koshiba

    Symmetry   13 ( 3 ) Article 511 - (29 pages)  2021年03月  [査読有り]  [国際誌]  [国際共著]

    担当区分:最終著者

    DOI

    Scopus

    10
    被引用数
    (Scopus)
  • Classification of indoor human fall events using deep learning

    Arifa Sultana, Kaushik Deb, Pranab Kumar Dhar, Takeshi Koshiba

    Entropy   23 ( 3 ) Article 328 - (20 pages)  2021年03月  [査読有り]  [国際共著]

    担当区分:最終著者

    DOI

    Scopus

    11
    被引用数
    (Scopus)
  • Fourier-based verifiable function secret sharing

    Takeshi Koshiba

    Proceedings of 2020 International Symposium on Information Theory and Its Applications (ISITA 2020)     442 - 446  2021年03月  [査読有り]

    担当区分:筆頭著者, 責任著者

    DOI

  • Traditional Bangladeshi Sports Video Classification Using Deep Learning Method

    Moumita Sen Sarma, Kaushik Deb, Pranab Kumar Dhar, Takeshi Koshiba

    Applied Sciences   11 ( 5 ) Article 2149 - (20 pages)  2021年02月  [査読有り]  [国際誌]  [国際共著]

    担当区分:最終著者

    DOI

    Scopus

    7
    被引用数
    (Scopus)
  • Image Defogging Framework Using Segmentation and the Dark Channel Prior

    Sabiha Anan, Mohammad Ibrahim Khan, Mir Md Saki Kowsar, Kaushik Deb, Pranab Kumar Dhar, Takeshi Koshiba

    Entropy   23 ( 3 ) Article 285 - (21 pages)  2021年02月  [査読有り]

    担当区分:最終著者

     概要を見る

    Foggy images suffer from low contrast and poor visibility problem along with little color information of the scene. It is imperative to remove fog from images as a pre-processing step in computer vision. The Dark Channel Prior (DCP) technique is a very promising defogging technique due to excellent restoring results for images containing no homogeneous region. However, having a large homogeneous region such as sky region, the restored images suffer from color distortion and block effects. Thus, to overcome the limitation of DCP method, we introduce a framework which is based on sky and non-sky region segmentation and restoring sky and non-sky parts separately. Here, isolation of the sky and non-sky part is done by using a binary mask formulated by floodfill algorithm. The foggy sky part is restored by using Contrast Limited Adaptive Histogram Equalization (CLAHE) and non-sky part by modified DCP. The restored parts are blended together for the resultant image. The proposed method is evaluated using both synthetic and real world foggy images against state of the art techniques. The experimental result shows that our proposed method provides better entropy value than other stated techniques along with have better natural visual effects while consuming much lower processing time.

    DOI

    Scopus

    8
    被引用数
    (Scopus)
  • A guests managing system with lattice-based verifier-local revocation group signature scheme with time-bound keys

    Maharage Nisansala Sevwandi Perera, Takeshi Koshiba

    Advances in Intelligent Systems and Computing (ICMC2019)   1170   81 - 96  2021年02月  [査読有り]

    担当区分:最終著者

    DOI

    Scopus

  • Efficient Private Conjunctive Query Protocol Over Encrypted Data

    Tushar Kanti Saha, Takeshi Koshiba

    Cryptography   5 ( 1 ) Article 2 - (28 pages)  2021年01月  [査読有り]  [国際誌]  [国際共著]

    担当区分:最終著者

    DOI

    Scopus

  • Enhanced Secure Comparison Schemes Using Homomorphic Encryption

    Lihua Wang, Tushar Kanti Saha, Yoshinori Aono, Takeshi Koshiba, Shiho Moriai

    Advances in Intelligent Systems and Computing   1264   211 - 224  2021年  [査読有り]  [国際共著]

    DOI

    Scopus

    3
    被引用数
    (Scopus)
  • Efficient protocols for private wildcards pattern matching

    Tushar Kanti Saha, Deevashwer Rathee, Takeshi Koshiba

    Journal of Information Security and Applications   55   Article 102609 - (18 pages)  2020年12月  [査読有り]  [国際誌]  [国際共著]

    担当区分:最終著者

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Almost fully secured lattice-based group signatures with verifier-local revocation

    Maharage Nisansala Sevwandi Perera, Takeshi Koshiba

    Cryptography   4 ( 4 ) Article 33 - (28 pages)  2020年11月  [査読有り]  [国際誌]

    担当区分:最終著者

    DOI

    Scopus

  • MCIC: Automated Identification of Cellulases from Metagenomic data and Characterization Based on Temperature and pH Dependence

    Mehdi Foroozandeh Shahraki, Shohreh Ariaeenejad, Fereshteh Fallah Atanaki, Behrouz Zolfaghari, Takeshi Koshiba, Kaveh Kavousi, Ghasem Hosseini Salekdeh

    Frontiers in Microbiology   11   Article 567863 - (10 pages)  2020年10月  [査読有り]  [国際誌]  [国際共著]

    DOI

    Scopus

    8
    被引用数
    (Scopus)
  • Combined interactive protocol for lattice-based group signature schemes with verifier-local revocation

    Maharage Nisansala Sevwandi Perera, Takeshi Koshiba

    International Journal of Grid and Utility Computing   11 ( 5 ) 662 - 673  2020年09月  [査読有り]  [国際誌]

    担当区分:最終著者

    DOI

  • Content delivery networks: State of the art, trends and future roadmap

    Behrouz Zolfaghari, Gautam Srivastava, Swapnoneel Roy, Hamid R. Nemati, Fatemeh Afghah, Takeshi Koshiba, Abolfazl Razi, Khodakhast Bibak, Pinaki Mitra, Brijesh Kumar Rai

    ACM Computing Surveys   53 ( 2 ) Article 34 - (34 pages)  2020年04月  [査読有り]  [国際誌]  [国際共著]

    DOI

    Scopus

    28
    被引用数
    (Scopus)
  • Blind audio watermarking based on parametric-slant Hadamard transform and Hessenberg decomposition

    Pranab Kumar Dhar, Azizul Hakim Chowdhury, Takeshi Koshiba

    Symmetry   12 ( 3 ) Article 333 - (16 pages)  2020年03月  [査読有り]  [国際誌]  [国際共著]

    担当区分:最終著者

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Blind image watermarking in canonical and cepstrum domains based on 4-connected t-o'clock scrambling

    Farhana Shirin Chowdhury, Pranab Kumar Dhar, Kaushik Deb, Takeshi Koshiba

    Symmetry   12 ( 2 ) Article 266 - (20 pages)  2020年02月  [査読有り]  [国際誌]  [国際共著]

    担当区分:最終著者

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • Generalized Mm,r-network: A case for fixed message dimensions

    Vikrant Singh, Behrouz Zolfaghari, Chunduri Venkata, Dheeraj Kumar, Brijesh Kumar Rai, Khodakhast Bibak, Gautam Srivastava, Swapnoneel Roy, Takeshi Koshiba

    IEEE Communications Letters   24 ( 1 ) 38 - 42  2020年01月  [査読有り]  [国際誌]  [国際共著]

    担当区分:最終著者

    DOI

    Scopus

  • Arbitrable blind quantum computation

    Go Sato, Takeshi Koshiba, Tomoyuki Morimae

    Quantum Information Processing   18 ( 12 ) Article 370 - (8 pages)  2019年12月  [査読有り]  [国際誌]

    担当区分:責任著者

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • Efficient private database queries using ring-LWE somewhat homomorphic encryption

    Tushar Kanti Saha, Mayank Rathee, Takeshi Koshiba

    Journal of Information Security and Applications   49   Article 102406 - (15 pages)  2019年12月  [査読有り]  [国際誌]  [国際共著]

    担当区分:最終著者

    DOI

    Scopus

    4
    被引用数
    (Scopus)
  • Perfectly secure message transmission against independent rational adversaries

    Kenji Yasugana, Takeshi Koshiba

    Lecture Notes in Computer Science (GameSec 2019)   11836   563 - 582  2019年10月  [査読有り]

    担当区分:最終著者

    DOI

    Scopus

  • Impossibility of perfectly-secure one-round delegated quantum computing for classical client

    Tomoyuki Morimae, Takeshi Koshiba

    Quantum Information & Computation   19 ( 3&4 ) 214 - 221  2019年03月  [査読有り]  [国際誌]

    担当区分:最終著者

  • New assumptions on isogenous pairing groups with applications to attribute-based encryption

    Takeshi Koshiba, Katsuyuki Takashima

    Lecture Notes in Computer Science (ICISC 2018)   11396   3 - 19  2019年01月  [招待有り]

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Outsourcing private equality tests to the cloud

    Tushar Kanti Saha, Takeshi Koshiba

    Journal of Information Security and Applications   43   83 - 98  2018年12月  [査読有り]  [国際誌]  [国際共著]

    担当区分:最終著者

    DOI

    Scopus

    4
    被引用数
    (Scopus)
  • Achieving strong security and member registration for lattice-based group signature scheme with verifier-local revocation

    Maharage Nisansala Sevwandi Perera, Takeshi Koshiba

    Journal of Internet Services and Information Security   8 ( 4 ) 1 - 15  2018年11月  [査読有り]  [国際誌]

    担当区分:最終著者

    DOI

  • Achieving strong security and verifier-local revocation for dynamic group signatures from lattice assumptions

    Maharage Nisansala Sevwandi Perera, Takeshi Koshiba

    Lecture Notes in Computer Science (STM 2018)   11091   3 - 19  2018年10月  [査読有り]

    DOI

    Scopus

    7
    被引用数
    (Scopus)
  • Almost-fully secured fully dynamic group signatures with efficient verifier-local revocation and time-bound keys

    Maharage Nisansala Sevwandi Perera, Takeshi Koshiba

    Lecture Notes in Computer Science (IDCS 2018)   11226   134 - 147  2018年10月  [査読有り]

    DOI

    Scopus

    3
    被引用数
    (Scopus)
  • Achieving full security for lattice-based group signatures with verifier-local revocation

    Maharage Nisansala Sevwandi Perera, Takeshi Koshiba

    Lecture Notes in Computer Science (ICICS 2018)   11149   287 - 302  2018年10月  [査読有り]

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • Perfectly secure message transmission against rational timid adversaries

    Maiki Fujita, Kenji Yasunaga, Takeshi Koshiba

    Lecture Notes in Computer Science (GameSec 2018)   11199   127 - 144  2018年10月  [査読有り]

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Fully dynamic group signature scheme with member registration and verifier-local revocation

    Maharage Nisansala Sevwandi Perera, Takeshi Koshiba

    Springer Proceedings in Mathematics & Statistics (Mathematics and Computing, ICMC 2018)   253   399 - 415  2018年09月  [査読有り]

    DOI

    Scopus

    15
    被引用数
    (Scopus)
  • Fourier-based function secret sharing with general access structure

    Takeshi Koshiba

    Springer Proceedings in Mathematics & Statistics (Mathematics and Computing, ICMC 2018)   253   417 - 428  2018年09月  [査読有り]

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • Zero-knowledge proof for lattice-based group signature schemes with verifier-local revocation

    Maharage Nisansala Sevwandi Perera, Takeshi Koshiba

    Lecture Notes on Data Engineering and Communications Technologies (TwCSec@NBiS 2018)   22   772 - 782  2018年09月  [査読有り]

    DOI

    Scopus

    9
    被引用数
    (Scopus)
  • Achieving almost-full security for lattice-based fully dynamic group signatures with verifier-local revocation

    Maharage Nisansala Sevwandi Perera, Takeshi Koshiba

    Lecture Notes in Computer Science (ISPEC 2018)   11125   229 - 247  2018年09月  [査読有り]

    DOI

    Scopus

    9
    被引用数
    (Scopus)
  • Private comparison protocol and its application to range queries

    Tushar Kanti Saha, Mayank, Deevashwer, Takeshi Koshiba

    Lecture Notes in Computer Science (IDCS 2017)   10794   128 - 141  2018年07月  [査読有り]

    DOI

  • Universal construction of cheater-identifiable secret sharing against rushing cheaters based on message authentication

    Masahito Hayashi, Takeshi Koshiba

    Proceedings of 2018 IEEE International Symposium on Information Theory (ISIT 2018)     2614 - 2618  2018年06月  [査読有り]

    DOI

    Scopus

    6
    被引用数
    (Scopus)
  • Non-transferable proxy re-encryption for multiple groups

    Ei Mon Cho, Lwin San, Takeshi Koshiba

    International Journal of Space-Based and Situated Computing   8 ( 1 ) 20 - 29  2018年04月  [査読有り]

    DOI

  • Privacy-preserving equality test towards big data

    Tushar Kanti Saha, Takeshi Koshiba

    Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)   10723   95 - 110  2018年  [査読有り]

     概要を見る

    In this paper, we review the problem of private batch equality test (PriBET) that was proposed by Saha and Koshiba (3rd APWConCSE 2016). They described this problem to find the equality of an integer within a set of integers between two parties who do not want to reveal their information if they do not equal. For this purpose, they proposed the PriBET protocol along with a packing method using the binary encoding of data. Their protocol was secured by using ring-LWE based somewhat homomorphic encryption (SwHE) in the semi-honest model. But this protocol is not fast enough to address the big data problem in some practical applications. To solve this problem, we propose a base-N fixed length encoding based PriBET protocol using SwHE in the same semi-honest model. Here we did our experiments for finding the equalities of 8–64-bit integers. Furthermore, our experiments show that our protocol is able to evaluate more than one million (resp. 862 thousand) of equality comparisons per minute for 8-bit (resp. 16-bit) integers with an encoding size of base 256 (resp. 65536). Besides, our protocol works more than 8–20 in magnitude than that of Saha and Koshiba.

    DOI

    Scopus

    3
    被引用数
    (Scopus)
  • Secure non-transferable proxy re-encryption for group membership and non-membership

    Ei Mon Cho, Lwin San, Takeshi Koshiba

    Lecture Notes on Data Engineering and Communications Technologies (TwCSec@NBiS 2017)   7   876 - 887  2017年08月  [査読有り]

    DOI

    Scopus

  • Function secret sharing using Fourier basis

    Takuya Ohsawa, Naruhiro Kurokawa, Takeshi Koshiba

    Lecture Notes on Data Engineering and Communications Technologies (TwCSec@NBiS 2017)   7   865 - 875  2017年08月  [査読有り]

    DOI

    Scopus

    3
    被引用数
    (Scopus)
  • An efficient privacy-preserving comparison protocol

    Tushar Kanti Saha, Takeshi Koshiba

    Lecture Notes on Data Engineering and Communications Technologies (NBiS 2017)   7   553 - 565  2017年08月  [査読有り]

    DOI

    Scopus

    6
    被引用数
    (Scopus)
  • Physical implementation of oblivious transfer using optical correlated randomness

    Tomohiro Ito, Hayato Koizumi, Nobumitsu Suzuki, Izumi Kakesu, Kento Iwakawa, Atsushi Uchida, Takeshi Koshiba, Jun Muramatsu, Kazuyuki Yoshimura, Masanobu Inubushi, Peter Davis

    SCIENTIFIC REPORTS   7   Article 8444 - (12 pages)  2017年08月  [査読有り]

     概要を見る

    We demonstrate physical implementation of information-theoretic secure oblivious transfer based on bounded observability using optical correlated randomness in semiconductor lasers driven by common random light broadcast over optical fibers. We demonstrate that the scheme can achieve one-out-of-two oblivious transfer with effective key generation rate of 110 kb/s. The results show that this scheme is a promising approach to achieve information-theoretic secure oblivious transfer over long distances for future applications of secure computation such as privacy-preserving database mining, auctions and electronic-voting.

    DOI

    Scopus

    4
    被引用数
    (Scopus)
  • Secure SMS transmission based on verifiable hash convergent group signcryption

    Ei Mon Cho, Takeshi Koshiba

    Proceedings - 18th IEEE International Conference on Mobile Data Management, MDM 2017     332 - 335  2017年06月  [査読有り]

     概要を見る

    Short Message Service (SMS) is one of the most popular services in the Global System for Mobile (GSM) and many challenges for security arise from the development of message transmission among the broadband network. Recently, an interesting technique called signcryption has been proposed, in which both the properties of signature (ownership) and encryption are simultaneously implemented, with better performance than the traditional signature-then-encryption approach. For the secure mobile computing, we propose a new method for two groups of users that send encrypted signed data by using SMS. We propose a new primitive called verifiable hash convergent group signcryption (VHCGS) by adding the properties of group signcryption and the verification facilities for the third party called the service provider. This research targets toward the type of applications in mobile computing and communication device concerning about SMS.

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • Private Equality Test Using Ring-LWE Somewhat Homomorphic Encryption

    Tushar Kanti Saha, Takeshi Koshiba

    Proceedings - Asia-Pacific World Congress on Computer Science and Engineering 2016 and Asia-Pacific World Congress on Engineering 2016, APWC on CSE/APWCE 2016     1 - 5  2017年06月  [査読有り]

     概要を見る

    We propose two secure protocols namely private equality test (PET) for single comparison and private batch equality test (PriBET) for batch comparisons of l-bit integers. We ensure the security of these secure protocols using somewhat homomorphic encryption (SwHE) based on ring learning with errors (ring-LWE) problem in the semi-honest model. In the PET protocol, we take two private integers input and produce the output denoting their equality or non-equality. Here the PriBET protocol is an extension of the PET protocol. So in the PriBET protocol, we take single private integer and another set of private integers as inputs and produce the output denoting whether single integer equals at least one integer in the set of integers or not. To serve this purpose, we also propose a new packing method for doing the batch equality test using few homomorphic multiplications of depth one. Here we have done our experiments at the 140-bit security level. For the lattice dimension 2048, our experiments show that the PET protocol is capable of doing any equality test of 8-bit to 2048-bit that require at most 107 milliseconds. Moreover, the PriBET protocol is capable of doing about 600 (resp., 300) equality comparisons per second for 32-bit (resp., 64-bit) integers. In addition, our experiments also show that the PriBET protocol can do more computations within the same time if the data size is smaller like 8-bit or 16-bit.

    DOI

    Scopus

    8
    被引用数
    (Scopus)
  • Fully Secure Lattice-based Group Signatures with Verifier-local Revocation

    M. Nisansala, S. Perera, Takeshi Koshiba

    2017 IEEE 31ST INTERNATIONAL CONFERENCE ON ADVANCED INFORMATION NETWORKING AND APPLICATIONS (AINA)     795 - 802  2017年  [査読有り]

     概要を見る

    In PKC 2014, Langlois et al. proposed the first lattice-based group signature scheme with the verifier-local revocability. The security of their scheme is selfless anonymity, which is weaker than the security model defined by Bellare, Micciancio and Warinschi (EUROCRYPT 2003). By using the technique in the group signature scheme proposed by Ling et al. ( PKC 2015), we propose a group signature scheme with the verifier-local revocability. For the security discussion of our scheme, we adapt the BMW03 model to cope with revocation queries, since the BMW03 model is for static groups. Then, we show that our scheme achieves the full anonymity in the adapted BMW03 model.

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • An Enhancement of Privacy-Preserving Wildcards Pattern Matching

    Tushar Kanti Saha, Takeshi Koshiba

    FOUNDATIONS AND PRACTICE OF SECURITY, FPS 2016   10128   145 - 160  2017年  [査読有り]

     概要を見る

    We consider secure pattern matching for some alphabet set, where gaps are represented by the character '*'. Generally, we know that a wildcard character '*' in the pattern is used to replace zero or more letters in the text. Yasuda et al. (ACISP 2014) proposed a new packing method for somewhat homomorphic encryption for handling wildcards pattern where the wildcards replace one letter in the text. We extend the secure pattern matching so that the wildcards are replaced with any sequences. We propose a method for privacy-preserving wildcards pattern matching using somewhat homomorphic encryption in the semi-honest model. At the same time, we also propose another packing method for executing homomorphic operations between plaintext and encrypted wildcards pattern in three homomorphic multiplications rather than 3k multiplications required by Yasuda et al. method to handle k sub-patterns. Moreover, we have been able to improve the communication complexity of Yasuda et al. method by a factor k denoting the total number of sub-patterns appearing in the pattern. In addition, our practical implementation shows that our method is about k-times faster than that of Yasuda et al. Here, we show some applications of our packing method to computing secure Hamming and Euclidean distances.

    DOI

    Scopus

    11
    被引用数
    (Scopus)
  • Analysis of decreasing squared-sum of Gram-Schmidt lengths for short lattice vectors.

    Masaya Yasuda, Kazuhiro Yokoyama, Takeshi Shimoyama, Jun Kogure, Takeshi Koshiba

    J. Mathematical Cryptology   11 ( 1 ) 1 - 24  2017年  [査読有り]  [国際誌]

    担当区分:最終著者

    DOI

    Scopus

    4
    被引用数
    (Scopus)
  • Secure Deduplication in a Multiple Group Signature Setting

    Ei Mon Cho, Takeshi Koshiba

    2017 IEEE 31ST INTERNATIONAL CONFERENCE ON ADVANCED INFORMATION NETWORKING AND APPLICATIONS (AINA)     811 - 818  2017年  [査読有り]

     概要を見る

    Multiple group setting schemes have recently become important for enabling deduplication for cloud servers. We consider a new primitive, cross-group deduplication, allowing the multiple groups by the group signature features. We propose a new framework DDUP-MUG (deduplication for the multiple-group signature scheme) that allows one or more groups to access a file such that the cloud storage server can avoid duplicates according to the ownership of the file. The main goal of the primitive is allowing to multiple groups with individual management and several clients from different groups who attempt to store an identical message on the server. In this paper, the group managers mainly manage the new entities and produce revocation lists for clients and the server respectively. We use Message Lock Encryption (MLE) as an ingredient for deduplication and we provide new three protocols, namely UPL-Dup (for uploading a new message), EDT-Dup (for editing the existing message) and DEL-Dup (for eliminating the existing message) in the DDUP-MUG framework.

    DOI

    Scopus

  • Private conjunctive query over encrypted data

    Tushar Kanti Saha, Takeshi Koshiba

    Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)   10239   149 - 164  2017年  [査読有り]

     概要を見る

    In this paper, we propose an efficient protocol to process a private conjunctive query over encrypted data in the cloud using the somewhat homomorphic encryption (SwHE) scheme with a batch technique. In 2016, Cheon, Kim, and Kim (CKK) [IEEE Trans. Inf. Forensics Security] showed conjunctive query processing over encrypted data using search-and-compute circuits and an SwHE scheme and mentioned that their scheme should be improved in performance. To improve the performance of processing a private conjunctive query, we also propose a new packing method to support an efficient batch computation for our protocol using a few multiplications. Our implementation shows that our protocol works more than 50 times as fast as the CKK protocol for conjunctive query processing. In addition, the security level of our protocol is better than the security level of the CKK protocol.

    DOI

    Scopus

    6
    被引用数
    (Scopus)
  • Big Data Cloud Deduplication based on Verifiable Hash Convergent Group Signcryption

    Ei Mon Cho, Takeshi Koshiba

    2017 THIRD IEEE INTERNATIONAL CONFERENCE ON BIG DATA COMPUTING SERVICE AND APPLICATIONS (IEEE BIGDATASERVICE 2017)     265 - 270  2017年  [査読有り]

     概要を見る

    As Big Data cloud storage servers are becoming popular the shortage of disk space in the cloud becomes a problem. Data deduplication is a method to control the explosion growth of data on the cloud and most of the storage providers are finding more secure and efficient methods for their sensitive data. Recently, an interesting technique called signcryption has been proposed, in which both the properties of signature (ownership) and encryption are simultaneously implemented, with better performance than the traditional signature-then-encryption approach. According to the deduplication, we introduce a new method for a group of users that can eliminate redundant encrypted data owned by different users. Furthermore, we generate the tag which will be the key component of big data management. We propose a new primitive group signcryption for deduplication called verifiable hash convergent group signcryption (VHCGS) by adding the properties of group signcryption and the verification facilities for the storage server (third party).

    DOI

    Scopus

    6
    被引用数
    (Scopus)
  • Efficient protocols for private database queries

    Tushar Kanti Saha, Mayank, Takeshi Koshiba

    Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)   10359   337 - 348  2017年  [査読有り]

     概要を見る

    We consider the problem of processing private database queries over encrypted data in the cloud. To do this, we propose a protocol for conjunctive query and another for disjunctive query processing using somewhat homomorphic encryption in the semi-honest model. In 2016, Kim et al. [IEEE Trans. on Dependable and Secure Comput.] showed an FHE-based query processing with equality conditions over encrypted data. We improve the performance of processing private conjunctive and disjunctive queries with the low-depth equality circuits than Kim et al.’s circuits. To get the low-depth circuits, we modify the packing methods of Saha and Koshiba [APWConCSE 2016] to support an efficient batch computation for our protocols with a few multiplications. Our implementation shows that our protocols work faster than Kim et al.’s protocols for both conjunctive and disjunctive query processing along with a better security level. We are also able to provide security to both attributes and values appeared in the predicate of the conjunctive and disjunctive queries whereas Kim et al. provided the security to the values only.

    DOI

    Scopus

    7
    被引用数
    (Scopus)
  • Privacy-Preserving Fuzzy Commitment for Biometrics via Layered Error-Correcting Codes

    Masaya Yasuda, Takeshi Shimoyama, Narishige Abe, Shigefumi Yamada, Takashi Shinzaki, Takeshi Koshiba

    FOUNDATIONS AND PRACTICE OF SECURITY (FPS 2015)   9482   117 - 133  2016年  [査読有り]

     概要を見る

    With the widespread development of biometrics, concerns about security and privacy are increasing. In biometrics, template protection technology aims to protect the confidentiality of biometric templates (i.e., enrolled biometric data) by certain conversion. The fuzzy commitment scheme gives a practical way to protect biometric templates using a conventional error-correcting code. The scheme has both concealing and binding of templates, but it has some privacy problems. Specifically, in case of successful matching, stored biometric templates can be revealed. To address such problems, we improve the scheme. Our improvement is to coat with two error-correcting codes. In particular, our scheme can conceal stored biometric templates even in successful matching. Our improved scheme requires just conventional error-correcting codes as in the original scheme, and hence it gives a practical solution for both template security and privacy of biometric templates.

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Secure Data Devolution: Practical Re-encryption with Auxiliary Data in LWE-based Somewhat Homomorphic Encryption.

    Masaya Yasuda, Takeshi Koshiba, Takeshi Shimoyama, Jun Kogure, Kazuhiro Yokoyama

    Proceedings of the 3rd ACM International Workshop on Security in Cloud Computing, SCC 2015     53 - 61  2015年  [査読有り]

    DOI

    Scopus

  • New packing method in somewhat homomorphic encryption and its applications.

    Masaya Yasuda, Takeshi Shimoyama, Jun Kogure, Kazuhiro Yokoyama, Takeshi Koshiba

    Security and Communication Networks   8 ( 13 ) 2194 - 2213  2015年  [査読有り]  [国際誌]

    担当区分:最終著者

    DOI

    Scopus

    29
    被引用数
    (Scopus)
  • Secure Statistical Analysis Using RLWE-Based Homomorphic Encryption.

    Masaya Yasuda, Takeshi Shimoyama, Jun Kogure, Kazuhiro Yokoyama, Takeshi Koshiba

    Lecture Notes in Computer Science (ACISP 2015)   9144   471 - 487  2015年  [査読有り]

    DOI

    Scopus

    19
    被引用数
    (Scopus)
  • Practical Packing Method in Somewhat Homomorphic Encryption

    Masaya Yasuda, Takeshi Shimoyama, Jun Kogure, Kazuhiro Yokoyama, Takeshi Koshiba

    DATA PRIVACY MANAGEMENT AND AUTONOMOUS SPONTANEOUS SECURITY, DPM 2013   8247   34 - 50  2014年  [査読有り]

     概要を見る

    Somewhat homomorphic encryption is public key encryption supporting a limited number of both additions and multiplications on encrypted data, which is useful for performing fundamental computations with protecting the data confidentiality. In this paper, we focus on the scheme proposed by Lauter, Naehrig and Vaikuntanathan (ACM CCSW 2011), and present two types of packed ciphertexts based on their packing technique. Combinations of two types of our packing method give practical size and performance for wider computations such as statistical analysis and distances. To demonstrate its efficiency, we implemented the scheme with our packing method for secure Hamming distance, which is often used in privacy-preserving biometrics. For secure Hamming distance between two binary vekoshiba@mail.saitama-u.ac.jpctors of 2048-bit, it takes 5.31ms on an Intel Xeon X3480 at 3.07 GHz. This gives the best performance in the state-of-the-art work using homomorphic encryption.

    DOI

    Scopus

    34
    被引用数
    (Scopus)
  • Privacy-Preserving Wildcards Pattern Matching Using Symmetric Somewhat Homomorphic Encryption

    Masaya Yasuda, Takeshi Shimoyama, Jun Kogure, Kazuhiro Yokoyama, Takeshi Koshiba

    INFORMATION SECURITY AND PRIVACY, ACISP 2014   8544   338 - 353  2014年  [査読有り]

     概要を見る

    The basic pattern matching problem is to find the locations where a pattern occurs in a text. We give several computations enabling a client to obtain matching results from a database so that the database can not learn any information about client's queried pattern. For such computations, we apply the symmetric-key variant scheme of somewhat homomorphic encryption proposed by Brakerski and Vaikuntanathan (CRYPTO 2011), which can support a limited number of both polynomial additions and multiplications on encrypted data. We also utilize the packing method introduced by Yasuda et al. (CCSW 2013) for efficiency. While they deal with only basic problems for binary vectors, we address more complex problems such as the approximate and wildcards pattern matching for non-binary vectors. To demonstrate the efficiency of our method, we implemented the encryption scheme for secure wildcards pattern matching of DNA sequences. Our implementation shows that a client can privately search real-world genomes of length 16,500 in under one second on a general-purpose PC.

    DOI

    Scopus

    24
    被引用数
    (Scopus)
  • On the exact decryption range for Gentry-Halevi's implementation of fully homomorphic encryption.

    Masaya Yasuda, Kazuhiro Yokoyama, Takeshi Shimoyama, Jun Kogure, Takeshi Koshiba

    J. Mathematical Cryptology   8 ( 3 ) 305 - 329  2014年  [査読有り]  [国際誌]

    担当区分:最終著者

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Ancilla-driven universal blind quantum computation

    Takahiro Sueki, Takeshi Koshiba, Tomoyuki Morimae

    PHYSICAL REVIEW A   87 ( 6 ) Article 060301(R) - (5 pages)  2013年06月  [査読有り]  [国際誌]

     概要を見る

    Blind quantum computation is a new quantum secure protocol, which enables Alice who does not have enough quantum technology to delegate her computation to Bob who has a fully fledged quantum power without revealing her input, output, and algorithm. So far, blind quantum computation has been considered only for the circuit model and the measurement-based model. Here we consider the possibility and the limitation of blind quantum computation in the ancilla-driven model, which is a hybrid of the circuit and the measurement-based models.

    DOI

    Scopus

    47
    被引用数
    (Scopus)
  • Secure pattern matching using somewhat homomorphic encryption.

    Masaya Yasuda, Takeshi Shimoyama, Jun Kogure, Kazuhiro Yokoyama, Takeshi Koshiba

    Proceedings of the ACM Conference on Computer and Communications Security (2013 ACM Cloud Computing Security Workshop, CCSW 2013)     65 - 76  2013年  [査読有り]

    DOI

    Scopus

    79
    被引用数
    (Scopus)
  • Packed Homomorphic Encryption Based on Ideal Lattices and Its Application to Biometrics.

    Masaya Yasuda, Takeshi Shimoyama, Jun Kogure, Kazuhiro Yokoyama, Takeshi Koshiba

    Lecture Notes in Computer Science (MoCrySEn 2013)   8128   55 - 74  2013年  [査読有り]

    DOI

    Scopus

    46
    被引用数
    (Scopus)
  • Computational Indistinguishability Between Quantum States and Its Cryptographic Application

    Akinori Kawachi, Takeshi Koshiba, Harumichi Nishimura, Tomoyuki Yamakami

    JOURNAL OF CRYPTOLOGY   25 ( 3 ) 528 - 555  2012年07月  [査読有り]  [国際誌]

     概要を見る

    We introduce a computational problem of distinguishing between two specific quantum states as a new cryptographic problem to design a quantum cryptographic scheme that is "secure" against any polynomial-time quantum adversary. Our problem, QSCD(ff), is to distinguish between two types of random coset states with a hidden permutation over the symmetric group of finite degree. This naturally generalizes the commonly-used distinction problem between two probability distributions in computational cryptography. As our major contribution, we show that QSCD(ff) has three properties of cryptographic interest: (i) QSCD(ff) has a trapdoor; (ii) the average-case hardness of QSCD(ff) coincides with its worst-case hardness; and (iii) QSCD(ff) is computationally at least as hard as the graph automorphism problem in the worst case. These cryptographic properties enable us to construct a quantum public-key cryptosystem which is likely to withstand any chosen plaintext attack of a polynomial-time quantum adversary. We further discuss a generalization of QSCD(ff), called QSCD(cyc), and introduce a multi-bit encryption scheme that relies on similar cryptographic properties of QSCD(cyc).

    DOI

    Scopus

    17
    被引用数
    (Scopus)
  • Public Discussion Must Be Back and Forth in Secure Message Transmission

    Takeshi Koshiba, Shinya Sawada

    INFORMATION SECURITY AND CRYPTOLOGY - ICISC 2010   6829   325 - 337  2011年  [査読有り]

     概要を見る

    Secure message transmission (SMT) is a two-party protocol between a sender and a receiver over a network in which the sender and the receiver are connected by 71 disjoint channels and t out of n channels can be controlled by an adaptive adversary with unlimited computational resources. If a public discussion channel is available to the sender and the receiver to communicate with each other then a secure and reliable communication is possible even when n &gt;= t + 1. The round complexity is one of the important measures for the efficiency for SMT. In this paper, we revisit the optimality and the impossibility for SMT with public discussion and discuss the limitation of SMT with the "unidirectional" public channel, where either the sender or the receiver can invoke the public channel, and show that the "bidirectional" public channel is necessary for SMT.

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Statistically-Hiding Quantum Bit Commitment from Approximable-Preimage-Size Quantum One-Way Function

    Takeshi Koshiba, Takanori Odaira

    THEORY OF QUANTUM COMPUTATION, COMMUNICATION, AND CRYPTOGRAPHY   5905   33 - 46  2009年  [査読有り]

     概要を見る

    We provide a quantum bit commitment scheme which has statistically-hiding and computationally-binding properties from any approximable-preimage-size quantum one-way function, which is a generalization of perfectly-hiding quantum bit commitment scheme based on quantum one-way permutation due to Dumais, Mayers and Salvail. in the classical case, statistically-hiding bit commitment scheme is constructible from any one-way function. However, it is known that the round complexity of the classical statistically-hiding bit commitment scheme is Omega(n/ log n) for the security parameter n. Our quantum scheme as well as the Dumais-Mayers-Salvail scheme is non-interactive, which is advantageous over the classical schemes.

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • Strengthening the Security of Distributed Oblivious Transfer

    K. Y. Cheong, Takeshi Koshiba, Shohei Nishiyama

    INFORMATION SECURITY AND PRIVACY, PROCEEDINGS   5594   377 - 388  2009年  [査読有り]

     概要を見る

    We study the distributed oblivious transfer first proposed by Naor and Pinkas in ASIACRYPT 2000, and generalized by Blundo et al. originally in SAC 2002 and Nikov et al. in INDOCRYPT 2002. One major objective of distributed oblivious transfer is to achieve information theoretic security under specified conditions through the distribution of the functions of traditional oblivious transfer to a set of neutral parties. In this paper we revise the definition of distributed oblivious transfer in order to deal with stronger adversaries and clarify possible ambiguities. Under the new definition, we observe some impossibility results and derive the tipper bounds for the system parameters (with respect to the size of coalition). The weak points of previously proposed schemes based on threshold secret sharing schemes using polynomial interpolation are reviewed and resolved. We generalize the results and prove that, by adjusting some technical details, a previous scheme proposed by Nikov et al. is unconditionally secure. This protocol is efficient and achieves the parameter bounds at the same time.

    DOI

    Scopus

    5
    被引用数
    (Scopus)
  • Reducing Complexity Assumptions for Oblivious Transfer

    K. Y. Cheong, Takeshi Koshiba

    ADVANCES IN INFORMATION AND COMPUTER SECURITY, PROCEEDINGS   5824   110 - 124  2009年  [査読有り]

     概要を見る

    Reducing the minimum assumptions needed to construct various cryptographic primitives is an important and interesting task in theoretical cryptography Oblivious transfer, one of the most basic cryptographic building blocks, could be also studied under this scenario. Reducing the minimum assumptions for oblivious transfer seems not an easy task, as there are a few impossibility results under black-box reductions
    Until recently, it is widely believed that oblivious transfer Can he constructed with trapdoor permutations Goldrech pointed out some flaw in the folklore and introduced some enhancement to cope with the flaw Haitner then revised the enhancement more properly. As a consequence they showed that some additional properties for trapdoor permutations are necessary to construct oblivious transfers In this paper, we discuss possibilities of basing not on trapdoor permutations but on trapdoor functions in general We generalize previous results and give an oblivious transfer protocol based on a collection of trapdoor functions with some extra properties with respect to the length-expansion and the pre- image size. We discuss that our reduced assumption is almost minimal and show the necessity for the extra properties.

    DOI

    Scopus

  • A combinatorial approach to deriving lower bounds for perfectly secure oblivious transfer reductions

    Kaoru Kurosawa, Wataru Kishimoto, Takeshi Koshiba

    IEEE Transactions on Information Theory   54 ( 6 ) 2566 - 2571  2008年06月  [査読有り]  [国際誌]

    担当区分:最終著者

     概要を見る

    Consider the scenario where we are given an ideal functionality of oblivious transfer (OT), and we wish to construct a larger OT by invoking the above functionality as a black box. How many invocations of an ideal OT functionality are necessary? In tackling this problem, some lower bounds were derived using entropy previously. In this paper, we manage to achieve tighter lower bounds by employing a combinatorial approach. This new approach yields lower bounds which are two times larger than the existing bounds. © 2008 IEEE.

    DOI

    Scopus

    5
    被引用数
    (Scopus)
  • Simple direct reduction of string (1,2)-OT to Rabin's OT without privacy, amplification

    Kaoru Kurosawa, Takeshi Koshiba

    INFORMATION THEORETIC SECURITY, PROCEEDINGS   5155   199 - +  2008年  [査読有り]

     概要を見る

    It is known that string (1, 2)-OT and Rabin's OT are equivalent. Actually, there have been many reductions between them. Many of them use the privacy amplification technique as a basic tool. The privacy amplification technique essentially involves some post-processing of sending random objects (e.g., random indices of pairwise independent hash functions) per each invocation of Rabin's OT is necessary. In this paper, we show a simple direct reduction of string (1, 2)-OT to Rabin's OT by using a deterministic randomness extractor for bit-fixing sources. Our reduction can be realized without privacy amplification and thus our protocol is simpler and more efficient with respect to the communication complexity than the previous reductions.

    DOI

    Scopus

  • More on security of public-key cryptosystems based on Chebyshev polynomials

    Kai Y. Cheong, Takeshi Koshiba

    IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS II-EXPRESS BRIEFS   54 ( 9 ) 795 - 799  2007年09月  [査読有り]  [国際誌]

    担当区分:最終著者

     概要を見る

    Recently, a public-key cryptosystem based on Cheby-shev polynomials has been proposed, but it has been later analyzed and shown insecure. This paper addresses some unanswered questions about the cryptosystem. We deal with the issue of computational precision. This is important for two reasons. Firstly, the cryptosystem is defined on. real numbers, but any practical data communication channel can only transmit a limited number of digits. Any real number can only be specified to some precision level, and we study the effect of that. Secondly, we show that the precision issue is related to its security. In particular, the algorithm previously proposed to break the cryptosystem may not work in some situations. Moreover, we introduce another method to break the cryptosystem with general precision settings. We extend the method to show that a certain class of cryptosystems is insecure. Our method is based on the known techniques on the shortest vector problem in lattice and linear congruences.

    DOI

    Scopus

    21
    被引用数
    (Scopus)
  • Low-density attack revisited

    Tetsuya Izu, Jun Kogure, Takeshi Koshiba, Takeshi Shimoyama

    DESIGNS CODES AND CRYPTOGRAPHY   43 ( 1 ) 47 - 59  2007年04月  [査読有り]  [国際誌]

     概要を見る

    The low-density attack proposed by Lagarias and Odlyzko is a powerful algorithm against the subset sum problem. The improvement algorithm due to Coster et al. would solve almost all the problems of density < 0.9408... in the asymptotical sense. On the other hand, the subset sum problem itself is known as an NP-hard problem, and a lot of efforts have been paid to establish public-key cryptosystems based on the problem. In these cryptosystems, densities of the subset sum problems should be higher than 0.9408... in order to avoid the low-density attack. For example, the Chor-Rivest cryptosystem adopted subset sum problems with relatively high densities. In this paper, we further improve the low-density attack by incorporating an idea that integral lattice points can be covered with polynomially many spheres of shorter radius and of lower dimension. As a result, the success probability of our attack can be higher than that of Coster et al.'s attack for fixed dimensions. The density bound is also improved for fixed dimensions. Moreover, we numerically show that our improved low-density attack makes the success probability higher in case of low Hamming weight solution, such as the Chor-Rivest cryptosystem, if we assume SVP oracle calls.

    DOI

    Scopus

    13
    被引用数
    (Scopus)
  • Progress in quantum computational cryptography

    Akinori Kawachi, Takeshi Koshiba

    JOURNAL OF UNIVERSAL COMPUTER SCIENCE   12 ( 6 ) 691 - 709  2006年  [査読有り]  [招待有り]

     概要を見る

    Shor's algorithms for the integer factorization and the discrete logarithm problems can be regarded as a negative effect of the quantum mechanism on public-key cryptography. From the computational point of view, his algorithms illustrate that quantum computation could be more powerful. It is natural to consider that the power of quantum computation could be exploited to withstand even quantum adversaries. Over the last decade, quantum cryptography has been discussed and developed even from the computational complexity-theoretic point of view. In this paper, we will survey what has been studied in quantum computational cryptography.

  • Universal test for quantum one-way permutations

    A Kawachi, H Kobayashi, T Koshiba, RH Putra

    THEORETICAL COMPUTER SCIENCE   345 ( 2-3 ) 370 - 385  2005年11月  [査読有り]

     概要を見る

    The next bit test was introduced by Blum and Micali and proved by Yao to be a universal test for cryptographic pseudorandom generators. On the other hand, no universal test for the cryptographic one-wayness of functions (or permutations) is known, although the existence of cryptographic pseudorandom generators is equivalent to that of cryptographic one-way functions. In the quantum computation model, Kashefi, Nishimura and Vedral gave a sufficient condition of (cryptographic) quantum one-way permutations and conjectured that the condition would be necessary. In this paper, we affirmatively settle their conjecture and complete a necessary and sufficient condition for quantum one-way permutations. The necessary and sufficient condition can be regarded as a universal test for quantum one-way permutations, since the condition is described as a collection of stepwise tests similar to the next bit test for pseudorandom generators. (c) 2005 Published by Elsevier B.V.

    DOI

    Scopus

    9
    被引用数
    (Scopus)
  • Computational indistinguishability between quantum states and its cryptographic application

    A Kawachi, T Koshiba, H Nishimura, T Yamakami

    ADVANCES IN CRYPTOLOGY - EUROCRYPT 2005,PROCEEDINGS   3494   268 - 284  2005年  [査読有り]

     概要を見る

    We introduce a problem of distinguishing between two quantum states as a new underlying problem to build a computational cryptographic scheme that is "secure" against quantum adversary. Our problem is a natural generalization of the distinguishability problem between two probability distributions, which are commonly used in computational cryptography. More precisely, our problem QSCD(ff) is the computational distinguishability problem between two types of random coset states with a hidden permutation over the symmetric group. We show that (i) QSCD(ff) has the trapdoor property; (ii) the average-case hardness of QSCD(ff) coincides with its worst-case hardness; and (iii) QSCD(ff) is at least as hard in the worst case as the graph automorphism problem. Moreover, we show that QSCD(ff) cannot be efficiently solved by any quantum algorithm that naturally extends Shor's factorization algorithm. These cryptographic properties of QSCD(ff) enable us to construct a public-key cryptosystem, which is likely to withstand any attack of a polynomial-time quantum adversary.

    DOI

    Scopus

    34
    被引用数
    (Scopus)
  • Theoretical analysis of (2)(X) attack on RC6

    M Takenaka, T Shimoyama, T Koshiba

    IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES   E87A ( 1 ) 28 - 36  2004年01月  [査読有り]

     概要を見る

    In this paper, we give a theoretical analysis of chi(2) attack proposed by Knudsen and Meier on the RC6 block cipher. To this end, we propose a method of security evaluation against chi(2) attack precisely including key dependency by introducing a method "Transition Matrix Computing." Previously, no theoretical security evaluation against chi(2) attack was known, it has been done by computer experiments. We should note that it is the first result concerning the way of security evaluation against chi(2) attack is shown theoretically.

  • Universal test for quantum one-way permutations

    A Kawachi, H Kobayashi, T Koshiba, RH Putra

    MATHEMATICAL FOUNDATIONS OF COMPUTER SCIENCE 2004, PROCEEDINGS   3153   839 - 850  2004年  [査読有り]

     概要を見る

    The next bit test was introduced by Blum and Micali and proved by Yao to be a universal test for cryptographic pseudorandom generators. On the other hand, no universal test for the cryptographic one-wayness of functions (or permutations) is known, though the existence of cryptographic pseudorandom generators is equivalent to that of cryptographic one-way functions. In the quantum computation model, Kashefi, Nishimura and Vedral gave a sufficient condition of (cryptographic) quantum one-way permutations and conjectured that the condition would be necessary. In this paper, we relax their sufficient condition and give a new condition that is necessary and sufficient for quantum one-way permutations. Our condition can be regarded as a universal test for quantum one-way permutations, since our condition is described as a collection of stepwise tests similar to the next bit test for pseudorandom generators.

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • Short exponent Diffie-Hellman problems

    T Koshiba, K Kurosawa

    PUBLIC KEY CRYPTOGRAPHY - PKC 2004, PROCEEDINGS   2947   173 - 186  2004年  [査読有り]

     概要を見る

    In this paper, we study short exponent Diffie-Hellman problems, where significantly many lower bits are zeros in the exponent. We first prove that the decisional version of this problem is as hard as two well known hard problems, the standard decisional Diffie-Hellman problem (DDH) and the short exponent discrete logarithm problem. It implies that we can improve the efficiency of ElGamal scheme and Cramer-Shoup scheme under the two widely accepted assumptions. We next derive a similar result for the computational version of this problem.

    DOI

    Scopus

    15
    被引用数
    (Scopus)
  • Theoretical analysis of χ2 attack on RC6

    Masahiko Takenaka, Takeshi Shimoyama, Takeshi Koshiba

    Lecture Notes in Computer Science (ACISP 2003)   2727   142 - 153  2003年  [査読有り]

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • Multiple linear cryptanalysis of a reduced round RC6

    T Shimoyama, M Takenaka, T Koshiba

    FAST SOFTWARE ENCRYPTION (REVISED PAPERS)   2365   76 - 88  2002年  [査読有り]

     概要を見る

    In this paper, we apply multiple linear cryptanalysis to a reduced round RC6 block cipher. We show that 18-round RC6 with weak key is breakable by using the multiple linear attack.

    DOI

    Scopus

    11
    被引用数
    (Scopus)
  • On sufficient randomness for secure public-key cryptosystems

    Takeshi Koshiba

    Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)   2274   34 - 47  2002年  [査読有り]

     概要を見る

    In this paper, we consider what condition is sufficient for random inputs to secure probabilistic public-key encryption schemes. Although a framework given in [16] enables us to discuss uniformly and comprehensively security notions of public-key encryption schemes even for the case where cryptographically weak pseudorandom generator is used as random nonce generator to encrypt single plaintext messages, the results are rather theoretical. Here we naturally generalize the framework in order to handle security for the situation where we want to encrypt many messages with the same key. We extend some results w.r.t. single message security in [16] – separation results between security notions and a non-trivial sufficient condition for the equivalence between security notions – to multiple messages security. Besides the generalization, we show another separation between security notions for k-tuple messages and for (k+1)-tuple messages. The natural generalization, obtained here, rather improves to understand the security of public-key encryption schemes and eases the discussion of the security of practical public-key encryption schemes. In other words, the framework contributes to elucidating the role of randomness in public-key encryption scheme. As application of results in the generalized framework, we consider compatibility between the ElGamal encryption scheme and some sequence generators. Especially, we consider the applicability of the linear congruential generator (LCG) to the ElGamal encryption scheme.

    DOI

    Scopus

    3
    被引用数
    (Scopus)
  • The Decision Diffie-Hellman assumption and the Quadratic Residuosity assumption

    T Saito, T Koshiba, A Yamamura

    IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES   E84A ( 1 ) 165 - 171  2001年01月  [査読有り]

     概要を見る

    This paper examines similarities between the Decision Diffie-Hellman (DDH) assumption and the Quadratic Residuosity (QR) assumption. In addition, we show that many cryptographic protocols based on the QR assumption can be reconstructed using the DDH assumption.

  • A new aspect for security notions: Secure randomness in public-key encryption schemes

    T Koshiba

    PUBLIC KEY CRYPTOGRAPHY, PROCEEDINGS   1992   87 - 103  2001年  [査読有り]

     概要を見る

    In this paper, we introduce a framework in which we can uniformly and comprehensively discuss security notions of public-key encryption schemes even for the case where some weak generator producing seemingly random sequences is used to encrypt plaintext messages. First, we prove that indistinguishability and semantic security are not equivalent in general. On the other hand, we derive some sufficient condition for the equivalence and show that polynomial-time pseudo-randomness is not always necessary for the equivalence.

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • Polynomial-time algorithms for the equivalence for one-way quantum finite automata

    T Koshiba

    ALGORITHMS AND COMPUTATION, PROCEEDINGS   2223   268 - 278  2001年  [査読有り]

     概要を見る

    Two quantum finite automata are equivalent if for any string x the two automata accept x with equal probability. This paper gives a polynomial-time algorithm for determining whether two measure-once one-way quantum finite automata are equivalent. The paper also gives a polynomial-time algorithm for determining whether two measure-many one-way quantum finite automata are equivalent.

    DOI

    Scopus

    8
    被引用数
    (Scopus)
  • A theory of randomness for public key cryptosystems: The ElGamal cryptosystem case

    T Koshiba

    IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES   E83A ( 4 ) 614 - 619  2000年04月  [査読有り]

     概要を見る

    There are many public key cryptosystems that require random inputs to encrypt messages and their security is always discussed assuming that random objects are ideally generated. Since cryptosystems run on computers, it is quite natural that these random objects are computationally generated. One theoretical solution is the use of pseudorandom generators in the Yao's sense [16]. Informally saying, the pseudorandom generators are polynomial-time algorithms whose outputs are computationally indistinguishable from the uniform distribution. Since if we use the Yao's generators then it takes much more time to generate pseudorandom objects than to encrypt messages in public key cryptosystems, we relax the conditions of pseudorandom generators to fit public key cryptosystems and give a minimal requirement for pseudorandom generators within public key cryptosystems. As an example, we discuss the security of the El-Gamal cryptosystem [7] with some well-known generators (e.g., the linear congruential generator). We also propose a new pseudorandom number generator, for random inputs to the ElGamal cryptosystem, that satisfies the minimal requirement. The newly proposed generator is based on the linear congruential generator. We show some evidence that the ElGamal cryptosystem with the proposed generator is secure.

  • A technique for boosting the security of cryptographic systems with one-way hash functions

    T Koshiba

    INFORMATION SECURITY AND CRYPTOLOGY - ICISC'99   1787   76 - 81  2000年  [査読有り]

     概要を見る

    In this paper, we show a practical solution to the problems where one-wayness of hash functions does not guarantee cryptographic systems to be secure enough. We strengthen the notion of one-wayness of hash functions and construct strongly one-way hash functions from any one-way hash function or any one-way function.

    DOI

    Scopus

  • Inferring pure context-free languages from positive data

    Takeshi Koshiba, Erkki Mäkinen, Yuji Takada

    Acta Cybernetica   14 ( 3 ) 469 - 477  2000年  [査読有り]  [国際誌]  [国際共著]

    担当区分:筆頭著者, 責任著者

  • Enhancing D-ABDUCTOR towards a diagrammatic user interface platform

    K Misue, K Nitta, K Sugiyama, T Koshiba, R Inder

    1998 SECOND INTERNATIONAL CONFERENCE ON KNOWLEDGE-BASED INTELLIGENT ELECTRONIC SYSTEMS, KES'98 PROCEEDINGS, VOL 1     359 - 368  1998年  [査読有り]

     概要を見る

    The D-ABDUCTOR system was originally developed as a diagram-based idea organizer with facilities for visualization and manipulation of a large class of graphs. It has since been enhanced to improve its extensibility, and now function exchange-ability, functional independence, and configurability without programming have become important features. The enhanced system and its features are illustrated with several examples of its application.

    DOI

  • Learning deterministic even linear languages from positive examples

    T Koshiba, E Makinen, Y Takada

    THEORETICAL COMPUTER SCIENCE   185 ( 1 ) 63 - 79  1997年10月  [査読有り]  [国際誌]  [国際共著]

    担当区分:筆頭著者, 責任著者

     概要を見る

    We consider the problem of learning deterministic even linear languages from positive examples, We show that, for any nonnegative integer k, the class of LR(k) even linear languages is not learnable from positive examples while there is a subclass called LRS(k), which is a natural subclass of LR(k) in the strong sense, learnable from positive examples. Our learning algorithm identifies this subclass in the limit with almost linear time in updating conjectures. As a corollary, in terms of even linear grammars, we have a learning algorithm for k-reversible languages that is more efficient than the one proposed by Angluin.

    DOI

    Scopus

    19
    被引用数
    (Scopus)
  • On a hierarchy of slender languages based on control sets

    Takeshi Koshiba

    Fundamenta Informaticae   31 ( 1 ) 41 - 47  1997年  [査読有り]  [国際誌]

    担当区分:筆頭著者, 責任著者

    DOI

  • Computational learning theoretic cryptanalysis of language theoretic cryptosystems

    Takeshi Koshiba

    Lecture Notes in Computer Science (ICICS 1997)   1334   28 - 38  1997年  [査読有り]

    DOI

  • A machine learning approach to knowledge acquisitions from text databases

    Y Sakakibara, K Misue, T Koshiba

    INTERNATIONAL JOURNAL OF HUMAN-COMPUTER INTERACTION   8 ( 3 ) 309 - 324  1996年07月  [査読有り]  [国際誌]

     概要を見る

    The rapid growth of data in large databases, such as text databases and scientific databases, requires efficient computer methods for automating analyses of the data with the goal of acquiring knowledges or making discoveries. Because the analyses of data are generally so expensive, most parts in databases remains as raw, unanalyzed primary data. Technology from machine learning (ML) will offer efficient tools for the intelligent analyses of the data using generalization ability. Generalization is an important ability specific to inductive learning that will predict unseen data with high accuracy based on learned concepts from training examples.
    In this article, we apply ML to text-database analyses and knowledge acquisitions from text databases. We propose a completely new approach to the problem of text classification and extracting keywords by using ML techniques. We introduce a class of representations for classifying text data based on decision trees; (i.e., decision trees over attributes on strings) and present an algorithm for learning them inductively. Our algorithm has the following features: It does not need any natural language processing technique and it is robust for noisy data. We show that our learning algorithm can be used for automatic extraction of keywords for text retrieval and automatic text categorization. We also demonstrate some experimental results using our algorithm on the problem of classifying bibliographic data and extracting keywords in order to show the effectiveness of our approach.

    DOI

    Scopus

  • Decision tree learning system with switching evaluator

    Takesih Koshiba

    Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)   1081   349 - 361  1996年  [査読有り]

     概要を見る

    In this paper, we introduce the notion of the local strategy of constructing decision trees that includes the information theoretic entropy algorithm in ID3 (or C4.5) and any other local algorithms. Simply put, given a sample, a local algorithm constructs a decision tree in the top-down manner using an evaluation function. We propose a new local algorithm that is very different from the entropy algorithm. We analyze behaviors of the two algorithms on a simple model. Based on these analyses, we propose a learning system of decision trees which can change an evaluation function while constructing decision trees, and verify the effect of the system by experiments with real databases. The system not only achieves a high accuracy, but also produces well-balanced decision trees, which have the advantage of fast classification.

    DOI

    Scopus

  • Typed pattern languages and their learnability

    Takeshi Koshiba

    Lecture Notes in Computer Science (EUROCOLT 1995)   904   367 - 379  1995年  [査読有り]

    DOI

    Scopus

    9
    被引用数
    (Scopus)
  • TEXT CLASSIFICATION AND KEYWORD EXTRACTION BY LEARNING DECISION TREES

    Y SAKAKIBARA, K MISUE, T KOSHIBA

    NINTH CONFERENCE ON ARTIFICIAL INTELLIGENCE FOR APPLICATIONS : PROCEEDINGS     466 - 466  1993年  [査読有り]

▼全件表示

書籍等出版物

  • Statistical Trend Analysis of Physically Unclonable Functions: An Approach via Text Mining

    Behrouz Zolfaghari, Khodakhast Bibak, Takeshi Koshiba, Hamid R. Nemati, Pinaki Mitra( 担当: 共著)

    CRC Press  2021年02月 ISBN: 036775455X

  • 観測に基づく量子計算

    小柴健史, 藤井啓祐, 森前智行

    コロナ社  2017年02月 ISBN: 9784339028706

  • 乱数生成と計算量理論

    小柴健史

    岩波書店  2014年11月 ISBN: 9784000069755

  • 確率と計算 ―乱択アルゴリズムと確率的解析―

    Michael Mitzenmacher, Eli Upfal, 小柴健史, 河内亮周( 担当: 共訳)

    共立出版  2009年04月 ISBN: 4320122291

     概要を見る

    高度な理論が必要な確率的検査証明の概念からパソコンのイーサネットカードの実設計まで,ランダム性と確率的手法は現代の計算機科学において主要な役割を果たしている。特にここ20年,確率論を計算機科学に導入する事例が急増している。そして計算機科学を広範かつより複雑な応用に適用できるように,より高度でより洗練された確率的技法が開発されてきている。そのような状況において,ネットワークアルゴリズム理論分野の第一級の研究者であるMichael Mitzenmacher とEli Upfal によって“Probability and Computing”が書き上げられた。本書はその邦訳版である。本書は,計算機科学に関連するランダム性の基本的手法である乱択アルゴリズムやアルゴリズムの確率的解析について詳しく解説している。

    ASIN

  • 量子暗号理論の展開

    小芦雅斗, 小柴健史

    サイエンス社  2008年11月

     概要を見る

    臨時別冊・数理科学 SGCライブラリ67
    第1章 量子鍵配送の基本プロトコル
    第2章 量子鍵配送の安全性とエンタングルメント
    第3章 量子鍵配送の安全性と相補性
    第4章 量子公開鍵暗号
    第5章 量子公開鍵暗号の安全性
    第6章 量子デジタル署名

Misc

  • 物理乱数生成の理論的側面

    小柴健史

    電子情報通信学会誌   94 ( 12 ) 1072 - 1076  2011年12月  [招待有り]

    記事・総説・解説・論説等(その他)  

    CiNii

  • 暗号論的擬似乱数

    小柴健史

    数理科学   519   21 - 25  2006年09月

  • Quantum Computational Cryptography

    Akinori Kawachi, Takeshi Koshiba

    H. Imai, M. Hayashi, eds., Quantum Computation and Information From Theory to Experiment (Topics in Applied Physics 102)     167 - 184  2006年07月

    記事・総説・解説・論説等(その他)  

    DOI

  • 量子コンピュータは公開鍵暗号にとって脅威なのか?

    小柴健史

    情報処理   47 ( 2 ) 159 - 168  2006年02月

     概要を見る

    量子コンピュータが実現すると素因数分解等を効率的に解くことができ, RSA暗号等の公開鍵暗号の解読が可能となってしまうことが知られている.量子暗号として有名な量子鍵配送プロトコルはその性質から, 公開鍵暗号にとって変わるものではない.では, 量子コンピュータが実現してしまった場合, 現在のセキュリティ基盤を支える公開鍵暗号系の技術は崩壊してしまうのであろうか?本稿では, 敵対者として量子コンピュータが存在したとしても安全性が保たれるような公開鍵暗号系の技術の最新動向について紹介する.

    CiNii

  • 現代暗号への量子アルゴリズムによる攻撃

    小柴健史

    数理科学   492   31 - 36  2004年06月

  • The Decision Diffie-Hellman Assumption and the Quadratic Residuosity Assumption

    SAITO Taiichi, KOSHIBA Takeshi, YAMAMURA Akihiro

    IEICE transactions on fundamentals of electronics, communications and computer sciences   84 ( 1 ) 165 - 171  2001年01月

     概要を見る

    This paper examines similarities between the Decision Diffie-Hellman (DDH) assumption and the Quadratic Residuosity (QR) assumption. In addition, we show that many cryptographic protocols based on the QR assumption can be reconstructed using the DDH assumption.

    CiNii

▼全件表示

Works(作品等)

  • ARMADA

    小柴健史  ソフトウェア 

    1987年
    -
    継続中

     概要を見る

    NEC PC-8001mkII用ゲーム

受賞

  • Award for Outstanding Research Achievement

    2018年12月   Asia Pacific Society for Computing and Information Technology  

  • Outstanding paper award

    2018年10月   GameSec 2018 (Conference on the Decision and Game Theory for Security)  

  • 基礎・境界ソサイエティ編集活動感謝状

    2011年09月   電子情報通信学会  

共同研究・競争的資金等の研究課題

  • 量子情報化社会に向けた量子計算基盤の構築

    日本学術振興会  科学研究費助成事業 基盤研究(A)

    研究期間:

    2021年04月
    -
    2026年03月
     

    小柴 健史, 河内 亮周, 田中 圭介, 安永 憲司, ルガル フランソワ, 西村 治道

  • フーリエ基底を用いた安全な関数分散技術の基盤構築

    日本学術振興会  科学研究費助成事業 挑戦的研究(萌芽)

    研究期間:

    2019年06月
    -
    2022年03月
     

    小柴 健史

     概要を見る

    関数分散は近年見出された新しい暗号技術であり,プライバシーを保ちつつ関数計算を分散評価させる技術で,マルチパーティ秘匿計算などに広く応用を持つと期待されている。その一方でその構築法は簡易ではなく分散させるための自由度が十分でないという問題点がある。本研究において,関数分散と呼ばれる暗号技術に新たな可能性を見出すことを目標として,関数がフーリエ関数の線型結合として表現される事実に着目する。まず,研究代表者自身によるフーリエ基底ベースの従来方式を統一的に扱うためのフレームワークを構築し,関数分散のための基盤整備を行なった。特に,少ない個数のフーリエ基底の線形結合で表現できる関数に対して,Monotone Span Program(MSP)を利用して実現されるアクセス構造を持つ線形秘密分散と組み合わせる方式の一般的性質について考察し,分散計算させるための自由度が高く,かつ,効率的に動作する関数分散を構築するための十分条件を得た。また,少ない個数のフーリエ基底の線形結合で表現でき,かつ「自然な」関数の候補としての定数段ブール回路について,フーリエ表現サイズと関数近似精度との関連について評価を行なった。さらに,秘密関数を持つディーラーが不正をはたらいてもその不正を一般ユーザが検出可能な検証可能秘密分散のアイデアを関数秘密分散に導入することを目指して,関数分散技術に要求される性質を抽出し,プロトタイププロトコルを構築した。

  • インセンティブを考慮した暗号基盤技術の構築

    日本学術振興会  科学研究費助成事業 基盤研究(B)

    研究期間:

    2017年04月
    -
    2021年03月
     

    田中 圭介, 河内 亮周, 安永 憲司, 小柴 健史

     概要を見る

    本研究の目的は、インセンティブの設計を様々な暗号技術 (電子署名・相手認証・ブロックチェーン技術) に拡張することである。このため、研究課題を2つ設定し、各課題に対して研究期間を大きく3つに分けている。課題(A)の既存暗号技術に対するインセンティブ設計では、合理的証明にもとづいた委託計算で利用されている報酬の技術的な設定手法を電子署名や相手認証などへ応用し、さらにその手法をその他の技術へ適用可能な形へ一般化させる。課題(B)のブロックチェーンに対するインセンティブ設計では、ブロックチェーンに対して適切にインセンティブを設定する手法を考案し、そのインセンティブの設定を、課題(A)で発展させたインセンティブの技術的設定手法で実現する。
    課題(A)に対しては、今年度は2018年度までに行った第1フェーズ「インセンティブ設計技法に関する調査と研究」で得られた知見を活用し、第2フェーズ「インセンティブを用いた電子署名・相手認証のモデルと技術の設計」を行った。今年度は特に、これらの要素に密接に関わるSecure Message Transmission (SMT)と呼ばれる要素に着目し、複数ある通信路がすべての敵に支配されたとしても、合理的な敵を考える場合には、安全に通信を行うことができることを示した。
    課題(B)に対しては、今年度は2018年度までに行った第1フェーズ「ブロックチェーンに関する調査と研究」で得られた知見を活用し、第2フェーズ「インセンティブを用いたブロックチェーンのモデルと技術の設計」を行った。典型的なproof-of-workにおいてはハッシュ関数の特定の要件を満たす値を出力するような入力を見つけることが行われている。これはある種の計算問題を解くことに対応しており、この問題を別の計算問題に置き換えたときのインセンティブ設計についての可能性についてに考察を行った。

  • 量子プロトコル理論の線的展開

    日本学術振興会  科学研究費助成事業 基盤研究(A)

    研究期間:

    2016年04月
    -
    2021年03月
     

    小柴 健史, 西村 治道, ルガル フランソワ, 田中 圭介, 河内 亮周, 安永 憲司, 松本 啓史, 堀山 貴史, 小林 弘忠

     概要を見る

    量子プロトコルに関しての基礎的研究として,量子計算機を持つと主張するサーバに対する量子計算機を持つかのクライアントによる古典的検証可能性に,報酬の概念を導入するモデルを提案し,ゲーム理論的な形での同課題の解決という新しい方向性を見出した。またクライアントがサーバに計算の内容を秘匿して量子計算をさせるブラインド量子計算の基本的な設定での不可能性を示し,さらに弱い量子計算モデルによるサンプリングの不可能性も示した。
    量子分散プロトコルの優位性の確立に向けては,大きな進展を得ることができた。具体的には,分散計算の中核的な問題である「全対最短経路問題」に対して,最良の古典分散プロトコルより高速な量子分散プロトコルの開発に成功した。帯域幅の限られているモデルにおいて,三角形発見問題を高速に解く量子分散プロトコルを構築できた。
    量子プロトコル理論へ基礎を与えるための古典暗号プロトコル研究でも貢献した。セキュアメッセージ伝達プロトコルについて,複数の独立した敵対者が存在するモデルでは,すべての通信路が支配されたとしてもゲーム理論的な安全性を達成できることを示した。これは,敵対者がすべての資源を支配した場合に自明に安全性が成り立たない古典的な安全性では実現できない結果である。さらに,並列計算が容易な効率の良いコミットメント方式を提案し,その耐量子安全性を評価した。情報理論的な安全性を持つ秘密計算の一種である条件付き秘密開示方式などの通信効率および使用乱数長の限界を評価した。

  • 通信複雑性に対するブラインド量子計算による方法論の確立

    日本学術振興会  科学研究費助成事業 挑戦的萌芽研究

    研究期間:

    2014年04月
    -
    2017年03月
     

    小柴 健史

     概要を見る

    幾つかの計算問題について量子通信複雑度を議論するために,比較対象として(古典秘匿計算の一方式としての)準同型暗号によるプライバシー保護データ検索の効率的なプロトコルを提案し計算機実験を通して実効性を確かめた。また,量子ブラインド計算において参加者が不正を行ったときに,情報理論的安全性を確保しつつ,それを第三者が検証できる仕組みを導入することに成功した。

  • 統計力学からの計算限界解明へのアプローチ

    日本学術振興会  科学研究費助成事業 新学術領域研究(研究領域提案型)

    研究期間:

    2012年06月
    -
    2017年03月
     

    渡辺 治, 安藤 映, 伊東 利哉, 小柴 健史, 山本 真基, 森 立平, 樺島 祥介, 福島 孝治

     概要を見る

    統計力学的な観点で提案されてきた計算の解析手法や計算に関する問題について,計算論的な観点から検討を行った。その結果,問題例の計算困難さの変化に関して,これまでの枠組みでは捉えられていなかった困難さの変化を明らにすることに成功し,計算困難さの変化を研究するための新しい,より頑健な枠組みを提案した。この結果は,暗号の安全性の基礎にもなる。一方,解の構造の特徴付けや,解の数え上げ問題など,統計力学の基本問題に関しても,効率的アルゴリズムの開発や,その基礎となる知見を得ることができた。

  • 量子プロトコル理論の深化

    日本学術振興会  科学研究費助成事業 基盤研究(A)

    研究期間:

    2012年04月
    -
    2016年03月
     

    小柴 健史, 河内 亮周, 田中 圭介, 安永 憲司, ルガル フランソワ, 松本 啓史, 小林 弘忠, 西村 治道

     概要を見る

    量子対話型証明の一般化モデルを提案し完全問題の存在やBabaiの崩壊定理の量子版などの計算量的構造を明らかにした。半環上の行列積およびグラフ上の三角形発見問題に対して高速量子アルゴリズムを構築し解析方法を発展させ量子分散プロトコルを構築した。観測系と計算系が分離可能な補助キュービット駆動型モデルでも量子ブラインド計算が実現することを示した。計算量クラスBQPの古典計算量クラスAWPPに対し事後選択の概念を利用した量子計算量クラスによる特徴付けを与えた。AWPPがBQPの最良上界である自然な理由を与えAWPPの研究への量子計算量理論的アプローチの可能性を切り拓いた。

  • マルチユーザ型量子ネットワーク

    日本学術振興会  科学研究費助成事業 基盤研究(A)

    研究期間:

    2011年04月
    -
    2016年03月
     

    林 正人, 小川 朋宏, 松本 隆太郎, 石坂 智, 小柴 健史, 西村 治道, 渡辺 峻

     概要を見る

    本研究では,ユーザが複数存在するネットワークにおける量子通信技術について研究を行った.特に,従来技術が苦手とする情報理論的な秘匿性について,量子通信技術をベースに研究した.情報理論的安全性を実現するには多くの場合、秘匿性増強とよばれる情報処理を符号を用いて行うが,先行研究では,1つの符号の長さの有限性を考慮した安全性評価は不十分であったため,それを明らかにした.さらに,秘匿性を保持した形で計算を依頼する秘匿依頼計算についても情報理論的安全性の枠組みで研究し,測定型量子計算の枠組みで具体的な手法を提案し,その計算結果の正しさを保証する枠組みを与えた.

  • 量子暗号理論と古典暗号理論の互換技法の開発

    日本学術振興会  科学研究費助成事業 挑戦的萌芽研究

    研究期間:

    2011年
    -
    2013年
     

    小柴 健史

     概要を見る

    一般的に観測ベース量子計算モデルで議論されるブラインド量子計算の特別形として観測に適した系と計算に適した系が存在し観測は観測系でのみ行う計算モデルとして補助キュービット駆動量子計算がある.当該モデルにおいてブラインド量子計算が可能であるための十分条件を導出し,実際にその十分条件を満たす方法を与えた.暗号理論においては,他のプロトコルの部品として利用しても安全性を維持する性質は汎用結合可能性と呼ばれる.ブラインド量子計算の方式には様々な方式があるが,クライアントが観測を行うタイプのFujii-Morimae方式は汎用結合可能であることを証明した.

  • 量子情報理論と量子計算量理論の融合技術の展開

    日本学術振興会  科学研究費助成事業 基盤研究(B)

    研究期間:

    2009年
    -
    2011年
     

    小柴 健史, 松本 啓史, 小林 弘忠, 田中 圭介, 河内 亮周

     概要を見る

    量子情報理論と量子計算量理論の融合技術を発展させて,対話型証明,暗号理論,ネットワーク理論などの諸問題に対して適用した.量子対話型証明に関しては,複数証明者間の量子エンタングルメントの効果を追究し,量子対話型証明の理論を発展させた.また,ネットワーク符号化における量子通信の可能性を検討し,効率化通信手法の提案を行った.従来の古典暗号の枠組みでは証明困難であったハードコア述語に対して量子暗号理論を介することでその証明を構築可能にした.量子暗号理論へのフィードバックを行うため,様々な古典暗号プロトコルの考案を行った.

  • 脱量子化手法の確立と暗号理論応用

    日本学術振興会  科学研究費助成事業 挑戦的萌芽研究

    研究期間:

    2008年
    -
    2010年
     

    小柴 健史

     概要を見る

    本研究課題では,アルゴリズム構築の新しいパラダイムとして「脱量子化手法」を確立することが目的であるが,前年度に着目した古典計算暗号技術でよく用いられているインタラクティブハッシングと呼ばれる技術とBB84量子鍵配送プロトコルで用いられているBB84量子状態との関係について,本年度はその応用研究を行った.両者の関係は量子化・脱量子化の関係にあり,まず,古典暗号理論における重要な定理の一つであるインタラクティブハッシュ定理の量子版として,非対話量子ハッシュ定理を導いた.これを応用し,量子一方向性関数に基づいて非対話形式の統計的秘匿性を持つ非対話の量子ビット委託プロトコルを構成することに成功した.古典暗号理論においては,ビット委託と紛失通信は大きく異なるプロトコルとして認識されているが,量子暗号においてはその親和性を示す状況証拠が得られていた.特に,F-束縛と呼ばれる特殊な束縛性を持つ文字列委託の存在を仮定した場合,量子紛失通信が得られることが知られており,F-束縛な文字列委託プロトコルをどのように構成すればよいのかは未解決問題のまま残されていた.量子一方向性関数に基づく非対話形式統計的秘匿ビット委託プロトコルを並列化することにより,F-束縛な文字列委託プロトコルを構成出来ることを示し,結果として,量子一方向性関数から量子紛失通信プロトコルを構成することに成功した.量子紛失通信は量子マルチパーティ計算につながると予想されるため,量子暗号理論においては量子一方向性関数の存在という妥当な仮定から高度な暗号プロトコルが構成できることを示唆するものとなっている.

  • 量子情報理論と量子計算量理論の融合とその応用

    日本学術振興会  科学研究費助成事業 基盤研究(B)

    研究期間:

    2006年
    -
    2008年
     

    小柴 健史, 松本 啓史, 小林 弘忠, 河内 亮周

     概要を見る

    量子情報処理を遂行できる実体の可能性・将来性について,対話型証明・暗号理論・アルゴリズム理論の観点から考察し,対話型証明においては量子エンタングルメントが有効であることを確認し,暗号理論においては非対話型のビット委託方式の提案を行い,アルゴリズム理論においては代表的な問題である隠れ部分群問題に対する量子アルゴリズムの限界を導出した.

▼全件表示

講演・口頭発表等

  • Guesswork of a quantum ensemble

    Michele Dall'Arno, Francesco Buscemi, Takeshi Koshiba

    25th Annual Conference on Quantum Information Processing (QIP 2022)  

    開催年月:
    2022年03月
     
     
  • Non-Interactive Statistically-Hiding Quantum Bit Commitment from any Quantum One-way Function

    Takeshi Koshiba  [招待有り]

    The 2nd Kyoto Workshop on Quantum Information, Computation and Foundation, QICF 2021   (オンライン)  the Quantum Information Unit and the Yukawa Institute for Theoretical Physics, Kyoto University  

    発表年月: 2021年09月

    開催年月:
    2021年09月
     
     
  • Guesswork of a quantum ensemble

    Michele Dall'Arno, Francesco Buscemi, Takeshi Koshiba

    The 21st Asian Quantum Information Science Conference, AQIS 2021   (オンライン) 

    発表年月: 2021年09月

    開催年月:
    2021年09月
     
     
  • On Public Verifiability for Secure Delegated Quantum Computation

    Takeshi Koshiba  [招待有り]

    The 1st Kyoto Workshop on Quantum Information, Computation, and Foundation, QICF 2020   (オンライン)  the Quantum Information Unit and Yukawa Institute for Theoretical Physics, Kyoto University  

    発表年月: 2020年09月

    開催年月:
    2020年09月
     
     
  • Recent Progress in Quantum Computational Cryptography

    Takeshi Koshiba  [招待有り]

    The 6th IEEE Conference on Computer Science and Data Engineering   (Melbourne) 

    発表年月: 2019年12月

  • On Public Verifiability for Secure Delegated Quantum Computation

    Takeshi Koshiba  [招待有り]

    研究集会「量子計算, ポスト量子暗号, 量子符号の融合と深化」   (福岡市)  マス・フォア・インダストリ研究所,九州大学  

    発表年月: 2019年11月

  • Homomorphic Encrypion and Its Applications

    Takeshi Koshiba  [招待有り]

    The 2018 International Conference for Top and Emerging Computer Scientists (IC-TECS 2018)   (Taipei)  Asia Pacific Society for Computing and Information Technology  

    発表年月: 2018年12月

  • 安全な代理量子計算

    小柴健史  [招待有り]

    情報理論研究会「若手研究者のための講演会」@第41回情報理論とその応用シンポジウム(SITA 2018)   (スパリゾートハワイアンズ, いわき市)  電子情報通信学会 情報理論とその応用サブソサイエティ  

    発表年月: 2018年12月

  • 観測に基づく量子計算と量子優位性

    小柴健史  [招待有り]

    CREST暗号数理 平成30年度第2回全体会議 チュートリアルワークショップ   (九州大学マスフォアインダストリ研究所, 福岡市) 

    発表年月: 2018年12月

  • 耐量子時代の擬似乱数生成

    小柴健史  [招待有り]

    Small-workshop on Communications between Academia and Industry for Security (SCAIS 2018)   (新潟市)  大阪大学、産業技術総合研究所  

    発表年月: 2018年01月

  • Secure Message Transmission : 可能性と限界

    小柴健史  [招待有り]

    第6回誤り訂正符号のワークショップ   電子情報通信学会 情報理論とその応用サブソサイエティ  

    発表年月: 2017年09月

  • Secure Message Transmission against Rational Adversaries

    Takeshi Koshiba  [招待有り]

    Cryptographic Technologies for Securing Network Storage and Their Mathematical Modeling   Institute of Mathematics for Industry, Kyushu University  

    発表年月: 2017年06月

  • Composable Security of Blind Computation

    Takeshi Koshiba  [招待有り]

    Quantum Science Symposium Asia 2013 (QSS-ASIA 2013)   (Tokyo Univ.) 

    発表年月: 2013年11月

  • Quantum Oblivious Transfer and Quantum One-Way Functions

    Takeshi Koshiba  [招待有り]

    Japan-Singapore Workshop on Multi-User Quantum Network   (National University of Singapore) 

    発表年月: 2012年09月

  • Interactive Hashing and BB84 States

    Takeshi Koshiba  [招待有り]

    Quatum Information in Paris   (Telecom Paris Tech) 

    発表年月: 2010年05月

  • On the Computational Power of BB84 States

    Takeshi Koshiba  [招待有り]

    2010 International Workshop on Quantum Information Science   (Tokyo Univ.) 

    発表年月: 2010年03月

  • Quantum Bit Commitment from Quantum One-Way Function

    Takeshi Koshiba  [招待有り]

    International Conference on Quantum Information and Technology   (Tokyo Univ.) 

    発表年月: 2009年12月

  • 一方向性関数からの擬似乱数生成器の構成法について

    小柴健史  [招待有り]

    第3回公開鍵暗号の安全な構成とその応用ワークショップ   (秋葉原)  産業技術総合研究所・情報セキュリティーセンター  

    発表年月: 2009年09月

  • An Unusual Short Introduction to Quantum Computing

    Takeshi Koshiba  [招待有り]

    (Selangor)  Universiti Putra Malaysia  

    発表年月: 2009年06月

  • Quantum Computational Bit Commitments

    Takeshi Koshiba  [招待有り]

    (Kuala Lumper)  International Islamic University Malaysia  

    発表年月: 2009年06月

  • An Old and New Direction to Quantum Cryptography

    Takeshi Koshiba  [招待有り]

    (Kuala Lumper)  MIMOS Berhad  

    発表年月: 2009年06月

  • On Quantum Oblivious Transfer

    Takeshi Koshiba  [招待有り]

    JST-CNRS Joint Workshop on Quantum Computation: Theory and Feasibility   (Institut Henri Poincare (IHP), Paris) 

    発表年月: 2008年09月

  • 量子計算入門

    小柴健史  [招待有り]

    非線形問題勉強会   (東京理科大学)  東京理科大学  

    発表年月: 2007年12月

  • 擬似乱数のつくりかた

    小柴健史  [招待有り]

    第312回情報科学セミナー   東京電機大学  

    発表年月: 2007年06月

  • 計算量理論的な量子暗号の進展

    小柴健史  [招待有り]

    第16回量子情報技術研究会 (QIT 16)   (NTT厚木) 

    発表年月: 2007年05月

  • 暗号理論における一方向性関数とその周辺の進展

    小柴健史  [招待有り]

    科学研究費特定領域研究「新世代の計算限界-その解明と打破-」Complexity研究集会   (東京工業大学) 

    発表年月: 2006年12月

  • Quantum Public Key Cryptosystem

    Takeshi Koshiba  [招待有り]

    Theory of Quantum Computation, Communication and Cryptography (TQC 2006)   (Atsugi) 

    発表年月: 2006年02月

  • 量子メカニズムと暗号通信

    小柴健史  [招待有り]

    第3回情報科学技術フォーラム (FIT2004)   (同志社大学) 

    発表年月: 2004年09月

▼全件表示

学内研究費(特定課題)

  • 量子情報理論的学習理論の数理基盤構築

    2021年  

     概要を見る

    The guesswork of a quantum ensemble quantifies the minimum number of guesses needed in average to correctly guess the state of the ensemble, when only one state can be queried at a time. Here, we derive analytical solutions of the guesswork problem subject to a finite set of conditions, including the analytical solution for any qubit ensemble with uniform probability distribution. As explicit examples, we compute the guesswork for any qubit regular polygonal and polyhedral ensemble.

  • ゲーム理論的合理性にもとづくセキュアメッセージ転送

    2019年   安永憲司

     概要を見る

    セキュアメッセージ転送は2者間の暗号プロトコルであり,複数の通信チャネルが利用でき,そのうちの幾つかの通信チャネルが敵対者に支配されたとしても,プライバシーを保ちつつメッセージを確実に伝達する方式である。経済的合理性を考慮したゲーム理論の観点から複数の独立した敵対者がある種の合理性をもって行動をしたとき,全チャネルが複数の敵対者に支配されたとしてもセキュアメッセージ転送が可能であることを示すことができた。これは,通常の暗号理論における敵対者の設定や経済的合理性の敵対者でも単一の敵対者の場合は不可能なことであり,この成果をセキュリティに関するゲーム理論的研究に関するトップ国際会議のGameSec2019で発表した。<!-- /* Font Definitions */ @font-face {font-family:"MS 明朝"; panose-1:2 2 6 9 4 2 5 8 3 4; mso-font-alt:"MS Mincho"; mso-font-charset:128; mso-generic-font-family:modern; mso-font-pitch:fixed; mso-font-signature:-536870145 1791491579 134217746 0 131231 0;}@font-face {font-family:Century; panose-1:2 4 6 4 5 5 5 2 3 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:647 0 0 0 159 0;}@font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:-536870145 1107305727 0 0 415 0;}@font-face {font-family:"\@MS 明朝"; panose-1:2 2 6 9 4 2 5 8 3 4; mso-font-charset:128; mso-generic-font-family:modern; mso-font-pitch:fixed; mso-font-signature:-536870145 1791491579 134217746 0 131231 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin:0mm; margin-bottom:.0001pt; text-align:justify; text-justify:inter-ideograph; mso-pagination:none; font-size:10.5pt; mso-bidi-font-size:11.0pt; font-family:"Century",serif; mso-fareast-font-family:"MS 明朝"; mso-bidi-font-family:"Times New Roman"; mso-font-kerning:1.0pt;}.MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt; font-family:"Century",serif; mso-ascii-font-family:Century; mso-fareast-font-family:"MS 明朝"; mso-hansi-font-family:Century; mso-font-kerning:0pt;}size:612.0pt 792.0pt; margin:99.25pt 30.0mm 30.0mm 30.0mm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;}div.WordSection1 {page:WordSection1;}<!-- /* Font Definitions */ @font-face {font-family:"MS 明朝"; panose-1:2 2 6 9 4 2 5 8 3 4; mso-font-alt:"MS Mincho"; mso-font-charset:128; mso-generic-font-family:modern; mso-font-pitch:fixed; mso-font-signature:-536870145 1791491579 134217746 0 131231 0;}@font-face {font-family:Century; panose-1:2 4 6 4 5 5 5 2 3 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:647 0 0 0 159 0;}@font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:-536870145 1107305727 0 0 415 0;}@font-face {font-family:"\@MS 明朝"; panose-1:2 2 6 9 4 2 5 8 3 4; mso-font-charset:128; mso-generic-font-family:modern; mso-font-pitch:fixed; mso-font-signature:-536870145 1791491579 134217746 0 131231 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin:0mm; margin-bottom:.0001pt; text-align:justify; text-justify:inter-ideograph; mso-pagination:none; font-size:10.5pt; mso-bidi-font-size:11.0pt; font-family:"Century",serif; mso-fareast-font-family:"MS 明朝"; mso-bidi-font-family:"Times New Roman"; mso-font-kerning:1.0pt;}.MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt; font-family:"Century",serif; mso-ascii-font-family:Century; mso-fareast-font-family:"MS 明朝"; mso-hansi-font-family:Century; mso-font-kerning:0pt;}size:612.0pt 792.0pt; margin:99.25pt 30.0mm 30.0mm 30.0mm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;}div.WordSection1 {page:WordSection1;}

  • セキュアメッセージ転送の限界突破のためのモデル条件緩和

    2018年   安永憲司

     概要を見る

    セキュアメッセージ転送は2者間の暗号プロトコルで,2者間の間に利用できるチャネルが複数存在し,複数存在するチャネル数の内何本かを敵に支配され,改ざん・盗聴を許す設定である。セキュアメッセージ転送が要求する性質は秘匿性と信頼性であり,両性質が完全な意味で達成される条件は2者間のチャネル数 Nと敵が支配するチャネル数Tの間にN≧2T+1を満たすことが必要であることが示されている。敵対者モデルとして経済的合理性に従い,かつ,妥当なモデルを構築し,そのモデルにおいては,N≧T+1の場合でも完全なセキュアメッセージ転送が構築できることを示すことに成功した。本成果はGameSec2018で研究発表し,Outstanding Paper Awardを受賞した。

  • 秘匿計算における鍵伝播機構の計算理論構築

    2018年   森前智行

     概要を見る

    量子計算の枠組みで秘匿代理計算を行う暗号プロトコルとしてBroadbent, Fitzsimons, Kashefiの方法(BFK09法)やその発展版であるHayashi&amp;Morimaeの方法(HM12法)がある。BFK09方法では量子情報を量子ワンタイムパッド法で完全秘匿を達成するのにパウリ行列X及びZをどう適用するのかという鍵情報を保持する。秘匿された量子情報に演算を施すことは鍵情報をどう変遷させるかに対応する。古典計算での実現可能性を究明するために鍵伝播メカニズムを解明することを考えた。両方法を解析した副産物として,古典クライアントではある種のブラインド量子計算は実現不可能であることを示した。

  • 秘匿計算における鍵伝播メカニズムの解明

    2017年   Go Sato, Tomoyuki Morimae

     概要を見る

    量子計算の枠組みで秘匿代理計算を行う暗号プロトコルとしてBroadbent, Fitzsimons, Kashefiの方法(BFK09法)がある。BFK09法では量子情報を量子ワンタイムパッド法で完全秘匿を達成するのにパウリ行列X及びZをどう適用するのかという鍵情報を保持する。秘匿された量子情報に演算を施すことは鍵情報をどう変遷させるかに対応する。古典計算での実現可能性を究明するためにBFK09法の鍵伝播メカニズムを解明することを考えた。その検討過程としてBFK09法の発展版のHayashi-Morimaeプロトコルを解析し,副産物として公開検証可能はブラインド量子計算プロトコルを考案した。

  • プライバシー保護可能な構造化クエリを許容する暗号化データベース

    2017年   Saha Tushar Kanti, Mayank

     概要を見る

    Ring LWE (Learning With Error)問題に基づく準同型暗号に対してデータ符号化法を工夫することで,ベクトルを暗号化したままの状態で内積計算の高速計算を実現する方法(報告者の既存研究成果)がある。この技術を応用し,暗号化データベース内の複数データエントリに対して,論理和や論理積を用いて構造的な条件を満たすデータを高速に抽出できるような方法を開発し,従来手法と計算機比較実験をすることで新手法の実効性を実証した。

▼全件表示

 

現在担当している科目

▼全件表示

担当経験のある科目(授業)

  • 情報数学3&4[アルゴリズムとデータ構造]

    早稲田大学  

    2021年04月
    -
    継続中
     

  • 応用数学4[計算理論]

    早稲田大学  

    2021年04月
    -
    継続中
     

  • 応用数学3[形式言語理論]

    早稲田大学  

    2021年04月
    -
    継続中
     

  • 情報数学特論I-2[暗号基礎理論 || ブール関数解析]

    早稲田大学,大学院  

    2017年04月
    -
    継続中
     

  • 情報数学特論I-1[量子計算]

    早稲田大学,大学院  

    2017年04月
    -
    継続中
     

  • コンピュータ数学2[近似アルゴリズム]

    早稲田大学,大学院  

    2017年04月
    -
    継続中
     

  • コンピュータ数学1[計算量理論]

    早稲田大学,大学院  

    2017年04月
    -
    継続中
     

  • 情報数学6[Javaプログラミング]

    早稲田大学  

    2017年04月
    -
    2021年03月
     

  • 情報数学5[コンピュータ概論]

    早稲田大学  

    2017年04月
    -
    2021年03月
     

  • 応用数学1&2[離散数学]

    早稲田大学  

    2017年04月
    -
    2021年03月
     

▼全件表示

 

社会貢献活動

  • 量子コンピューター時代の情報セキュリティ

    会津大学  夢の科学技術を子供たちの手に−シンポジウム2006  (会津大学) 

    2006年11月
    -
     

メディア報道

  • 未来の情報化社会を守る

    新聞・雑誌

    執筆者: 本人以外  

    埼玉新聞  

    サイ・テクこらむ  

    2014年04月

  • [Future Story] 絶対に破れない量子暗号

    会誌・広報誌

    執筆者: 本人以外  

    三機工業株式会社広報部   Harmony  

    No.44, pp.12-13  

    2009年03月