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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

Security Analysis of the Pomykała-Barabasz Scheme

Li F., Hu Y.

Fundamenta Informaticae

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2007

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Vol. 80, nr 4

453-459

EN

In 2006, Pomykala and Barabasz [Fundamenta Informaticae 69 (2006) 411–425] proposed an elliptic curve based threshold proxy signature scheme which requires shorter cryptographic keys.They claimed that their scheme satisfies the secrecy, the proxy protected, the unforgeability, the non-repudiation, and the known signers. However, in this paper, we show that their scheme cannot achieve the proxy protected, the unforgeability and the non-repudiation by demonstrating a conspiracy attack. In this attack, any t malicious proxy signers can collusively impersonate some other proxy signers to generate proxy signatures.

3

An Efficient and Practical (t, n) Threshold Proxy Signature Scheme with Known Signers

Huang H-F., Chang C-C.

Fundamenta Informaticae

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2003

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Vol. 56, nr 3

243-253

EN

Previously, all of the proposed threshold proxy signature schemes which have been based on the discrete logarithms required a protocol to generate and verify a shared secret among the proxy group. Therefore, it is necessary for the proxy signers to execute a lot of expensive modular exponential computations and communications to obtain and verify a shared secret. Thus, it is very time-consuming to construct the proxy signature. Moreover, some of the existing threshold proxy signature schemes reveal that the receiver cannot find out who signed the proxy signatures. In this paper, we proposed a practical, efficient, and low communications (t, n) threshold proxy signature scheme based on RSA cryptosystem. By using our way, not only the original signer can know who generated the proxy signature, but also everyone can be a verifier to certify the actuality of the group signers who made it. So, it is very convenient to clarify the responsibility of the document's signers fairly.

4

Cryptanalysis of the Hwang-Shi Proxy Signature Scheme

Hwang M-S., Lee C-C., Hwang S-J.

Fundamenta Informaticae

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2002

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Vol. 53, nr 2

131-134

EN

Recently, Hwang and Shi proposed an efficient proxy signature scheme without using one-way hash functions. In their scheme, an original signer needn't send a proxy certificate to a proxy signer through secure channels. However, there are two public key substitution methods that can be used to attack their scheme. In this article, we show that their scheme is vulnerable to the public key substitution attacks.