An improvement of nonrepudiable threshold proxy signature scheme with known signers
In a (t, n) threshold proxy signature scheme which is a variant of the proxy signature scheme, the proxy signature key is shared among a group of n proxy signers delegated by the original signer. Any t or more proxy signers can cooperatively sign messages on behalf of the original signer. In 2000, Hwang et al. (Int J Inf 11 (2000) 1) proposed a secure nonrepudiable threshold proxy signature scheme with known signers. In this paper, we point out a cryptanalysis of their scheme. Furthermore, we improve the security of the threshold proxy signature scheme which remedies the weakness of Hwang et al.'s scheme. (C) 2004 Elsevier Ltd. All rights reserved.
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