科研之友
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摘要
In a multi-proxy signature scheme, an original signer delegates his or her signing capability to a group of proxy signers, in such a way that only the cooperation of all the proxy signers can generate a valid proxy signature on behalf of the original signer. Several multi-proxy signature schemes have been proposed so far. However, these works either only provide informal security analysis, or provide a security proof in the random oracle model, which has received a lot of criticism that the proofs in the random oracle model are not proofs. In this paper, we propose a new construction of multi-proxy signature that can be proven secure without using the random oracles. As for the security, we divide the potential adversaries into three kinds according to their attack power, and prove that the proposed scheme is unforgeable against all kinds of adversaries, assuming the Computational Diffie-Hellman problem is intractable. Furthermore, the new scheme has the property that the size of a multi-proxy signature is independent on the number of the proxy signers. As far as we know, this is the first multi-proxy signature scheme that can be proven secure in the standard model.
