Browsing by Author "Fan, Chun-I"

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Interdomain Identity-Based Key Agreement Schemes
(2014-01-01)
Fan, Chun-I
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Lin, Yi-Hui
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Hsu, Tuan-Hung
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Hsu, Ruei-Hau
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交大工研院聯合研發中心
In order to simplify key management, two-party and three-party key agreement schemes based on user identities have been proposed recently. Multiparty (including more than three parties) key agreement protocols, which also are called conference key schemes, can be applied to distributed systems and wireless environments, such as ad hoc networks, for the purpose of multiparty secure communication. However, it is hard to extend two- or three-party schemes to multiparty ones with the guarantee of efficiency and security. In addition to the above two properties, interdomain environments should also be considered in key agreement systems due to diversified network domains. However, only few identity-based multiparty conference key agreement schemes for single domain environments and none for interdomain environments were proposed in the literature and they did not satisfy all of the security attributes such as forward secrecy and withstanding impersonation. In this paper, we will propose a novel efficient single domain identity-based multiparty conference key scheme and extend it to an interdomain one. Finally, we prove that the proposed schemes satisfy the required security attributes via formal methods.
Strongly Secure Certificate less Signature: Cryptanalysis and Improvement of Two Schemes
(2015-01-01)
Chen, Yu-Chi
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Tso, Raylin
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Horng, Gowboa
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Fan, Chun-I
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Hsu, Ruei-Hau
Certificateless cryptography is a well-known system to avoid the key escrow problem of identity-based cryptography. Since it was introduced by Al-Riyami and Paterson in 2003, plenty of schemes and security models had been presented and discussed. Particularly, certificateless signature (CLS) is the most lightened to attract research attention. In the literature works, Hu et al. introduced generic construction and security model that can satisfy non-repudiation. On the other hand, Huang et al. simulated possible attacks and defined more complete security models of CLS for existential unforgeability, and they sorted adversaries into normal, strong, and super adversaries (ordered by their attack powers). In this paper, we consider the security of CLS schemes regarding both of existential unforgeability and non-repudiation. We not only show the weaknesses of two CLS schemes of Fan et al. [5] and Xiong et al. [13], but also point out the loopholes of their security proofs. Hence, we improve the weaknesses and loopholes by proposing a new certificateless short signature with low bandwidth. The proposed scheme is provably secure against the super adversaries and reaches the highest security level.