| 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)
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| Research Abstract |
This research is on the identity-based cryptosystems for realization of mail-type cipher communication. First, we investigated a realization scheme of identity-based non-interactive key sharing, and obtained two new original ideas by which we could establish two new realization schemes of identity-based cryptosystem. As the result, the most important problem of key sharing on the common-key cryptosystem could be solved, and it became possile to apply the common-key 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 common-key is shared, (c) any common-key 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 common-key is equivalent to that of encryption of RSA public-key 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 identity-based non-interactive key sharing scheme has been eatablished, it becomes possible to apply it for many cryptographic systems such as identity-based cryptosystem, identity-based authentication, electronic voting system, key management, etc. Less
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