| Co-Investigator(Kenkyū-buntansha) |
SAKURAI Koichi Department of Computer Science and Communication Engineering, Kyushu Univ. professor, 工学部, 助教授 (60264066)
ITO Toshiya School of Information Science, Japanese Advanced Institution of Science and Technology Research Associate, 総合理工学研究科, 助教授 (20184674)
SHINODA Yoichi School of Information Science, Japanese Advanced Institution of Science and Technology Research Associate, 情報科学研究科, 助教授 (50206108)
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| Budget Amount *help |
¥5,700,000 (Direct Cost: ¥5,700,000)
Fiscal Year 2000: ¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 1999: ¥3,200,000 (Direct Cost: ¥3,200,000)
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| Research Abstract |
In this reseach, we have proposed ＆ threshold (secret sharing) scheme, in which without reconstructing the system, one can efficiently and securely update the parameter such as the threshold and the number of the members. With Tamura et. al., we have presented a threshold scheme with parameter changeability, in which the systems before and after such a update keep the perfect security. But that system requires much amount of information which should be distributed using secure channels. With Meda et. al., we have constructed a threshold scheme with threshold changeability, in which the amount of information which should be securely distributed, can be decreased, though the perfect security is lost,
With Okamoto et. al, we have modified "Okamoto-Tanaka key-exchange scheme (OT scheme)" so that we can update a key without reconstructing the system. Also we have estimated the security of the modified system. With Kim et. al., we have given the proof for the security of OT scheme against various types of active attacks.
With Burmester et. al., we have proposed "an order-specified multisignature scheme", and given a proof of the security of the scheme. With Minato et. al., we have proposed "a multisignature with signers' intensions", and given a proof of the security of the scheme.
With Koide et. al., we have proposed an e-cash system, in which even if the secret key of the bank leaks, the bank can dinstinguish a valid coin with a coin forged using the leaked secret key.
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