Research on IdentityBased Cryptosystems
Project/Area Number  05680315 
Research Category 
GrantinAid for General Scientific Research (C)

Allocation Type  Singleyear Grants 
Research Field 
情報システム学(含情報図書館学)

Research Institution  Kobe University 
Principal Investigator 
TANAKA Hatsukazu Faculty of Engineering Kobe University Electrical & Electronics Eng.Professor, 工学部, 教授 (80031144)

Project Period (FY) 
1993 – 1994

Project Status 
Completed(Fiscal Year 1994)

Budget Amount *help 
¥1,800,000 (Direct Cost : ¥1,800,000)
Fiscal Year 1994 : ¥400,000 (Direct Cost : ¥400,000)
Fiscal Year 1993 : ¥1,400,000 (Direct Cost : ¥1,400,000)

Keywords  Cryptosystem / Identity Information / Discrete Logarithm Problem / KeySharing / Factoring / RSA PublicKey Cryptosystem / User Authenication System / Key Management / ユークリッド・アタック 
Research Abstract 
This research is on the identitybased cryptosystems for realization of mailtype cipher communication. First, we investigated a realization scheme of identitybased noninteractive key sharing, and obtained two new original ideas by which we could establish two new realization schemes of identitybased cryptosystem. As the result, the most important problem of key sharing on the commonkey cryptosystem could be solved, and it became possile to apply the commonkey cryptosystem easily. The first realization scheme is such that the number of calculations performed by the key generation center is a few, but the amount of secret informations kept secretly by each user increases slightly. The original basic idea is as follows : (a) the security depends on the difficulty of factoring (i.e.computationally secure), (b) the proper random numbers to each user can be cancelled simultaneously when a commonkey is shared, (c) any commonkey between the third parties can not be forged even if many u
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sers collude. The second realization scheme neede to solve the logarithm problem with a relatively small prime as a modulus when each user's secret information is generated, and then the number of necessary calculations increaes slightly, but the number of secret informations for each user is only two words of size N and the number of calculations necessary for sharing a commonkey is equivalent to that of encryption of RSA publickey cryptosystem. The original basic ides is as follows : (a) the security depends on the difficulty of factoring and solving the discrete logarithm problem, (b) a trapdoor can be provided to the discrete logarithm problem using the difficulty of factoring, (c) any secret information of the other party can not be disclosed by the key sharing equation. As the identitybased noninteractive key sharing scheme has been eatablished, it becomes possible to apply it for many cryptographic systems such as identitybased cryptosystem, identitybased authentication, electronic voting system, key management, etc. Less

Report
(3results)
Research Output
(9results)