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Identity-Based Multi-Proxy Signature Scheme in the Standard Model

Gu K., Jia W., Zhang J.

Fundamenta Informaticae

2017

Vol. 150, nr 2

179--210

Multi-proxy signature is a variant of proxy signature, which allows that a delegator (original signer) may delegate his signing rights to many proxy signers. Comparing with proxy signatures, multi-proxy signatures can effectively prevent that some of proxy signers abuse signing rights. Also, with the rapid development of identity-based cryptography, identity-based multi-proxy signature (IBMPS) schemes have been proposed. Comparing with proxy signature based on public key cryptography, IBMPS can simplify key management and be used for more applications. Presently, many identity-based multi-proxy signature schemes have been proposed, but most of them are constructed in the random oracle model. Also, the existing security model for identity-based multi-proxy signature is not enough complete according to the Boldyreva et al.’s work. In this paper, we present a framework for IBMPS on n + 1 users (n is the number of proxy signers participating in signing), and show a detailed security model for IBMPS. Under our framework, we present an identity-based multi-proxy signature scheme in the standard model. Comparing with other identity-based multi-proxy signature schemes, the proposed scheme has more complete security.

Cryptanalysis and Improvement of a Certificateless Multi-proxy Signature Scheme

Tian M., Yang W., Huang L.

Fundamenta Informaticae

2014

Vol. 129, nr 4

365--375

Certificateless cryptography is a new type of public key cryptography,which removes the certificate management problem in traditional public key cryptography and the key escrow problem in identity-based public key cryptography. Multi-proxy signature is an extension of proxy signature, which allows an original signer authorizing a group of proxy signers and only the cooperation of all proxy signers in the group can create valid proxy signatures on behalf of the original signer. Recently, Jin andWen combined certificateless cryptographywith multi-proxy signature, and proposed a model as well as a concrete scheme of certificateless multi-proxy signature. They claimed that their scheme is provably secure in their security model. Unfortunately, in this paper by giving two attacks, we will show that their certificateless multi-proxy signature scheme can be broken. The first attack indicates their security model is flawed and the second attack indicates their certificateless multi-proxy signature scheme is insecure. Possible improvements are also suggested to prevent these attacks.