Kohtaro TADAKI


Proposal of the Multivariate Public Key Cryptosystem Relying on the Difficulty of Factoring a Product of Two Large Prime Numbers
Shigeo TSUJII Kohtaro TADAKI Ryo FUJITA Masahito GOTAISHI 
Publication:   IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 2016/01/01
Vol. E99-A  No. 1  pp. 66-72
Type of Manuscript:  Special Section PAPER (Special Section on Cryptography and Information Security)
Category: 
Keyword: 
Multivariate Public Key CryptosystemPublic Key Cryptosystemprime factorizationGröbner basesrank attack
 Summary | Full Text:PDF(1.3MB)

Dually-Perturbed Matsumoto-Imai Signature (DPMS) Scheme
Masahito GOTAISHI Kohtaro TADAKI Ryo FUJITA Shigeo TSUJII 
Publication:   IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 2010/06/01
Vol. E93-A  No. 6  pp. 1078-1085
Type of Manuscript:  Special Section PAPER (Special Section on Discrete Mathematics and Its Applications)
Category: Cryptography and Information Security
Keyword: 
post-quantum cryptosystemMultivariate Public Key Cryptosystemdigital signature
 Summary | Full Text:PDF(650.6KB)

Key-Generation Algorithms for Linear Piece In Hand Matrix Method
Kohtaro TADAKI Shigeo TSUJII 
Publication:   IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 2010/06/01
Vol. E93-A  No. 6  pp. 1102-1110
Type of Manuscript:  Special Section PAPER (Special Section on Discrete Mathematics and Its Applications)
Category: Cryptography and Information Security
Keyword: 
multivariate public-key cryptosystemPiece In Hand matrix methodplus methodkey-generation algorithmprobabilistic polynomial-time algorithmlinear algebra
 Summary | Full Text:PDF(371.2KB)

Security Enhancement of Various MPKCs by 2-Layer Nonlinear Piece in Hand Method
Shigeo TSUJII Kohtaro TADAKI Ryou FUJITA Masahito GOTAISHI Toshinobu KANEKO 
Publication:   IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 2009/10/01
Vol. E92-A  No. 10  pp. 2438-2446
Type of Manuscript:  Special Section PAPER (Special Section on Information Theory and Its Applications)
Category: Cryptography and Information Security
Keyword: 
public key cryptosystemmultivariate public key cryptosystemPiece in Handmultivariate polynomial
 Summary | Full Text:PDF(399.2KB)

Proposal for Piece in Hand Matrix: General Concept for Enhancing Security of Multivariate Public Key Cryptosystems
Shigeo TSUJII Kohtaro TADAKI Ryou FUJITA 
Publication:   IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 2007/05/01
Vol. E90-A  No. 5  pp. 992-999
Type of Manuscript:  Special Section PAPER (Special Section on Discrete Mathematics and Its Applications)
Category: 
Keyword: 
public key cryptosystemmultivariate polynomialmultivariate public key cryptosystempiece in hand conceptsoldiers in hand
 Summary | Full Text:PDF(242.5KB)