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1

Certificateless Proxy Signature Scheme in the Standard Model

Ming Y., Wang Y.

Fundamenta Informaticae

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2018

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Vol. 160, nr 4

409--445

EN

Proxy signature is extension of the standard signature, in which the original signer can delegate his or her signing capability to proxy signer in such a way that the latter can sign messages on behalf of the former. Certificateless cryptography eliminates the need of certificates in the traditional public key cryptography and solves the inherent key escrow problem in the identity based cryptography. In this paper, we extend security model of proxy signature to certificateless setting and formalize the security model of certificateless proxy signature. We propose a certificateless proxy signature scheme with concrete implementation which is probably secure in the standard model. Furthermore, the proposed scheme is proven to be existentially unforgeable under the hardness of the computational Diffie-Hellman problem.

2

Cryptanalysis and Improvement of a Certificateless Multi-proxy Signature Scheme

Tian M., Yang W., Huang L.

Fundamenta Informaticae

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2014

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Vol. 129, nr 4

365--375

EN

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.

3

An efficient provably secure certificateless aggregate signature applicable to mobile computation

Xiong H., Wu Q., Chen Z.

Control and Cybernetics

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2012

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Vol. 41, no. 2

373-391

EN

An aggregate signature scheme allows a public algorithm to aggregate n signatures on n distinct messages from n signers into a single signature. By validating the single resulting signature, one can be convinced that the messages have been endorsed by all the signers. Certificateless aggregate signatures allow the signers to authenticate messages without suffering from the complex certificate management in the traditional public key cryptography or the key escrow problem in identity-based cryptography. In this paper, we present a new efficient certificateless aggregate signature scheme. Compared with up-to-date certificateless aggregate signatures, our scheme is equipped with a number of attracting features: (1) it is shown to be secure under the standard computational Diffie-Hellman assumption in the random oracle model; (2) the security is proven in the strongest security model so far; (3) the signers do not need to be synchronized; and (4) its performance is comparable to the most efficient up-to-date schemes. These features are desirable in a mobile networking and computing environment where the storage/ computation capacity of the end devices are limited, and due to the wireless connection and distributed feature, the computing devices are easy to be attacked and hard to be synchronized.