Proxy signature schemes based on factoring

The proxy signature schemes allow proxy signers to sign messages on behalf of an original signer, a company or an organization. However, most of existing proxy signature schemes are based on the discrete logarithm problem. In this paper, the author would like to propose two efficient proxy signature schemes based on the factoring problem, which combine the RSA signature scheme and the Guillou-Quisquater signature scheme. One is a proxy-unprotected signature scheme that is more efficient. No matter how many proxy signers cooperatively sign a message, the computation load for verifiers would remain almost constant. The other is a proxy-protected signature scheme that is more secure. Finally, to protect the privacy of proxy signers, the author proposes a proxy-protected signature scheme with anonymous proxy signers. (C) 2002 Elsevier Science B.V. All rights reserved.