Zuowen Tan

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A (t, n) threshold proxy signature scheme enables an original signer to delegate the signature authority to a proxy group of n member such that t or more than t proxy signers can cooperatively sign messages on behalf of the original signer. In the paper, we review the security of some nonre-pudiable threshold proxy signature schemes with known signers. We(More)
In this paper, we first show that a previous proxy signature scheme by delegation with certificate is not provably secure under adaptive-chosen message attacks and adaptive-chosen warrant attacks. The scheme does not provide the strong undeniability. Then we construct a proxy signature scheme by delegation with certificate based on Co-GDH group from(More)
Authenticated multiple key exchange (AMKE) protocols not only allow participants to warrant multiple session keys within one run of the protocol but also ensure the authenticity of the other party. Many AMKE protocols using bilinear pairings have been proposed. However, the relative computation cost of the pairing is approximately twenty times higher than(More)
—Recently, Yang et al. proposed a three-party encrypted key exchange protocol (3PAKE) which is based on Elliptic curve cryptography. Their 3PAKE protocol is efficient because it requires less computation cost and less communication cost, which is well suitable for mobile commerce environments. However, Yang et al.'s 3PAKE protocol is susceptible to parallel(More)
—In the internet environment, it is desirable for a user to login different servers by keying the same password and using the same smart card. This paper proposes an authentication and key agreement scheme with key confirmation for multi-server environments. Compared with the previous authentication and key agreement schemes for multi-server environments,(More)
The telecare medicine information system enables the patients gain health monitoring at home and access medical services over internet or mobile networks. In recent years, the schemes based on cryptography have been proposed to address the security and privacy issues in the telecare medicine information systems. However, many schemes are insecure or they(More)