Kenji KOYAMA


Fast Computation over Elliptic Curves E(Fqn) Based on Optimal Addition Sequences
Yukio TSURUOKA Kenji KOYAMA 
Publication:   IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 2001/01/01
Vol. E84-A  No. 1  pp. 114-119
Type of Manuscript:  Special Section PAPER (Special Section on Cryptography and Information Security)
Category: 
Keyword: 
elliptic curvesscalar multiplicationFrobenius mapaddition chains
 Summary | Full Text:PDF(352.7KB)

Two Discrete Log Algorithms for Super-Anomalous Elliptic Curves and Their Applications
Noboru KUNIHIRO Kenji KOYAMA 
Publication:   IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 2000/01/25
Vol. E83-A  No. 1  pp. 10-16
Type of Manuscript:  Special Section PAPER (Special Section on Cryptography and Information Security)
Category: 
Keyword: 
elliptic curve discrete logarithm problemsuper-anomalous elliptic curvesdeterministic polynomial time algorithm
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Improved Elliptic Curve Methods for Factoring and Their Performance
Hidenori KUWAKADO Kenji KOYAMA 
Publication:   IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 1997/01/25
Vol. E80-A  No. 1  pp. 25-33
Type of Manuscript:  Special Section PAPER (Special Section on Cryptography and Information Security)
Category: 
Keyword: 
factorizationelliptic curvebirthday paradox
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Fast Exponentiation Algorithms Based on Batch-Processing and Precomputation
Yukio TSURUOKA Kenji KOYAMA 
Publication:   IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 1997/01/25
Vol. E80-A  No. 1  pp. 34-39
Type of Manuscript:  Special Section PAPER (Special Section on Cryptography and Information Security)
Category: 
Keyword: 
addition chains
 Summary | Full Text:PDF(451.1KB)

A New Version of FEAL, Stronger against Differential Cryptanalysis*
Routo TERADA Paulo G. PINHEIRO Kenji KOYAMA 
Publication:   IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 1996/01/25
Vol. E79-A  No. 1  pp. 28-34
Type of Manuscript:  Special Section PAPER (Special Section on Cryptography and Information Security)
Category: 
Keyword: 
cryptographyblock cipherdifferential cryptanalysiskey breaking
 Summary | Full Text:PDF(608.6KB)

The Security of an RDES Cryptosystem against Linear Cryptanalysis
Yasushi NAKAO Toshinobu KANEKO Kenji KOYAMA Routo TERADA 
Publication:   IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 1996/01/25
Vol. E79-A  No. 1  pp. 12-19
Type of Manuscript:  Special Section PAPER (Special Section on Cryptography and Information Security)
Category: 
Keyword: 
linear cryptanalysissecret key cryptosystemDESprobabilistic swappingbest expression
 Summary | Full Text:PDF(593.9KB)

A New RSA-Type Scheme Based on Singular Cubic Curves (y-αx)(y-βx)x3(mod n)
Hidenori KUWAKADO Kenji KOYAMA 
Publication:   IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 1996/01/25
Vol. E79-A  No. 1  pp. 49-53
Type of Manuscript:  Special Section PAPER (Special Section on Cryptography and Information Security)
Category: 
Keyword: 
public-key cryptosystemthe RSA schemecubic curves
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On the Solutions of the Diophantine Equation x3y3z3n
Kenji KOYAMA 
Publication:   IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 1995/03/25
Vol. E78-A  No. 3  pp. 444-449
Type of Manuscript:  LETTER
Category: Information Security and Cryptography
Keyword: 
Diophantine equationsearch algorithm
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A New RSA-Type Scheme Based on Singular Cubic Curves y2x3+bx2 (mod n)
Hidenori KUWAKADO Kenji KOYAMA Yukio TSURUOKA 
Publication:   IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 1995/01/25
Vol. E78-A  No. 1  pp. 27-33
Type of Manuscript:  Special Section PAPER (Special Section on Cryptography and Information Security)
Category: 
Keyword: 
cryptographyRSA cryptosystemcubic curve
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Dynamic Swapping Schemes and Differential Cryptanalysis
Toshinobu KANEKO Kenji KOYAMA Routo TERADA 
Publication:   IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 1994/08/25
Vol. E77-A  No. 8  pp. 1328-1336
Type of Manuscript:  Special Section PAPER (Special Section on Information Theory and Its Applications)
Category: 
Keyword: 
differential cryptanalysissecret key cryptosystemDEScharacteristic probabilitydynamic swapping scheme
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Efficient Cryptosystems over Elliptic Curves Based on a Product of Form-Free Primes
Hidenori KUWAKADO Kenji KOYAMA 
Publication:   IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 1994/08/25
Vol. E77-A  No. 8  pp. 1309-1318
Type of Manuscript:  Special Section PAPER (Special Section on Information Theory and Its Applications)
Category: 
Keyword: 
cryptographypublic-keyelliptic curvesfactorization
 Summary | Full Text:PDF(830.8KB)

Demonstrating Possession without Revealing Factors
Hiroki SHIZUYA Kenji KOYAMA Toshiya ITOH 
Publication:   IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 1994/01/25
Vol. E77-A  No. 1  pp. 39-46
Type of Manuscript:  Special Section PAPER (Special Section on Cryptography and Information Security)
Category: 
Keyword: 
zero-knowledge prooffactoringdiscrete logarithm
 Summary | Full Text:PDF(610KB)

FOREWORD
Kenji KOYAMA 
Publication:   IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 1994/01/25
Vol. E77-A  No. 1  pp. 1-1
Type of Manuscript:  FOREWORD
Category: 
Keyword: 
 Summary | Full Text:PDF(78.3KB)

How to Strengthen DES-like Cryptosystems against Differential Cryptanalysis
Kenji KOYAMA Routo TERADA 
Publication:   IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 1993/01/25
Vol. E76-A  No. 1  pp. 63-69
Type of Manuscript:  Special Section PAPER (Special Section on Cryptography and Information Security)
Category: 
Keyword: 
DEScryptanalysisdifferential attackprobabilistic swapping
 Summary | Full Text:PDF(562.8KB)

A Signed Binary Window Method for Fast Computing over Elliptic Curves
Kenji KOYAMA Yukio TSURUOKA 
Publication:   IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 1993/01/25
Vol. E76-A  No. 1  pp. 55-62
Type of Manuscript:  Special Section PAPER (Special Section on Cryptography and Information Security)
Category: 
Keyword: 
addition chainelliptic curves
 Summary | Full Text:PDF(585.9KB)

Elliptic Curve Cryptosytems and Their Applications
Kenji KOYAMA Tatsuaki OKAMOTO 
Publication:   IEICE TRANSACTIONS on Information and Systems
Publication Date: 1992/01/25
Vol. E75-D  No. 1  pp. 50-57
Type of Manuscript:  Special Section PAPER (Special Section on Theoretical Foundations of Computing)
Category: 
Keyword: 
public-key cryptosystemelliptic curvefactoring
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Security and Unique Decipherability of Two-Dimensional Public Key Cryptosystems
Kenji KOYAMA 
Publication:   IEICE TRANSACTIONS (1976-1990)
Publication Date: 1990/07/25
Vol. E73-E  No. 7  pp. 1058-1067
Type of Manuscript:  Special Section PAPER (Special Issue on Cryptography and Information Security)
Category: Public-Key Systems
Keyword: 
 Summary | Full Text:PDF(659.8KB)

The Number of Extended k-th Power Residues mod pm
Kenji KOYAMA 
Publication:   IEICE TRANSACTIONS (1976-1990)
Publication Date: 1986/12/25
Vol. E69-E  No. 12  pp. 1267-1270
Type of Manuscript:  LETTER
Category: Mathematics, Combinatorics and Graph Theory
Keyword: 
 Summary | Full Text:PDF(259.4KB)

Cryptographic Key Sharing Methods for Multi-Groups and Security Analysis
Kenji KOYAMA 
Publication:   IEICE TRANSACTIONS (1976-1990)
Publication Date: 1983/01/25
Vol. E66-E  No. 1  pp. 13-20
Type of Manuscript:  PAPER
Category: Data Transmission
Keyword: 
 Summary | Full Text:PDF(483.7KB)