Abstract

. Delegation of rights is a common practice in the real world. Proxy signature schemes have been invented to delegate signing capability efficiently and transparently. Existing proxy signature schemes don't support nonrepudiation. Nonrepudiation means signature signer, both the original and proxy signers, cannot falsely deny later that he generated a signature. In practice, it is important and, sometimes, necessary to have the capability to decide who is the actual signer of a proxy signature for internal auditing purpose or when there is abuse of signing capability. In this paper, we show how to add nonrepudiation to existing proxy signature schemes. Nonrepudiation is achieved through a partially blind signature key generation protocol adapted from a fully blind signature scheme. The new nonrepudiable proxy signature scheme fits in the same general framework as existing ones. Therefore, the desirable properties of existing schemes can also be said about our new scheme. In...

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