A (t,n) threshold proxy signature scheme allows t or more proxy signers from a designated group of n proxy signers to sign messages on behalf of an original signer. A threshold proxy signature scheme with the nonrepudiation property is a scheme with the capability that any verifier can identify the proxy group which is responsible for a proxy signature, while the proxy group cannot deny. So far, there have been two threshold proxy signature schemes proposed. Of these, Kim's scheme is nonrepudiable, but Zhang's scheme is not. Ln these two schemes, the t proxy signers from the group who actually sign the message are unknown and unidentified. This is very inconvenient for auditing purposes. For the responsibility of the actual signers and the traceability of adversarial signers, it is sometimes necessary to identify who the actual signers are. In this article, we propose the nonrepudiable threshold proxy signature scheme with known signers which is a nonrepudiable threshold proxy signature scheme with the property that the actual signers from the proxy group are known and identified. (C) 1999 Elsevier Science B.V. All rights reserved.
