Cryptanalysis of the Hwang-Shi Proxy Signature Scheme

[[abstract]]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[[notice]]補正完畢[[journaltype]]國外[[incitationindex]]EI[[booktype]]紙本[[booktype]]電子版[[countrycodes]]NL

Cryptanalysis and Performance Evaluation of Enhanced Threshold Proxy Signature Scheme Based on RSA for Known Signers

In these days there are plenty of signature schemes such as the threshold proxy signature scheme (Kumar and Verma 2010). The network is a shared medium so that the weakness security attacks such as eavesdropping, replay attack, and modification attack. Thus, we have to establish a common key for encrypting/decrypting our communications over an insecure network. In this scheme, a threshold proxy signature scheme based on RSA, any or more proxy signers can cooperatively generate a proxy signature while or fewer of them cannot do it. The threshold proxy signature scheme uses the RSA cryptosystem to generate the private and the public key of the signers (Rivest et al., 1978). Comparison is done on the basis of time complexity, space complexity, and communication overhead. We compare the performance of four schemes (Hwang et al. (2003), Kuo and Chen (2005), Yong-Jun et al. (2007), and Li et al. (2007), with the performance of a scheme that has been proposed earlier by the authors of this paper. In the proposed scheme, both the combiner and the secret share holder can verify the correctness of the information that they are receiving from each other. Therefore, the enhanced threshold proxy signature scheme is secure and efficient against notorious conspiracy attacks

Comments on "A practical (t, n) threshold proxy signature scheme based on the RSA cryptosystem"

In a (t, n) proxy signature scheme, the original signer can delegate his/her signing capability to n proxy signers such that any t or more proxy singers can sign messages on behalf of the former, but t 1 or less of them cannot do the same thing

Security Analysis of a Proxy Signature Scheme over Braid Groups

Delegation of powers is a common practice in the real world. To realized the delegation of powers electronically, Mambo,Usuda and Okamoto proposed the first proxy signature scheme in 1996. Since then a number of new schemes and their improvements have been proposed. In 2008, Verma proposed a proxy signature scheme over braid groups. This paper analyzes Vermas scheme and found that this scheme suffers with the serious security flaws. In this scheme,the proxy signer is able to misuse his delegated signing capabilities and the original signer can not restrict the proxy signer for misuse her delegation power. As a result, the proposed scheme does not satisfy some essential security requirements. Vermas proposed scheme is also not secure against the original signer and proxy singer changing attacks. Thus, the proposed scheme is not only insecure against the attacks by original signer and proxy signer but also has pitfalls against the forgery attacks mounted by any antagonist

Security Analysis of Some Proxy Signature

A proxy signature scheme allows an entity to delegate his/her signing capability to another entity in such a way that the latter can sign messages on behalf of the former. Such schemes have been suggested for use in a number of applications, particularly in distributed computing where delegation of rights is quite common. Followed by the rst schemes introduced by Mambo, Usuda and Okamoto in 1996, a number of new schemes and improvements have been proposed. In this paper, we present a security analysis of four such schemes newly proposed in [15, 16]. By successfully identifying several interesting forgery attacks, we show that all the four schemes are insecure. Consequently, the fully distributed proxy scheme in [11] is also insecure since it is based on the (insecure) LKK scheme [14, 15]. In addition, we point out the reasons why the security proofs provided in [15] are invalid

An Efficient Secure Anonymous Proxy Signature Scheme

Proxy signature schemes can be used in many business applications such as when the original signer is not present to sign important documents. Any proxy signature scheme has to meet the identifiability, undeniability, verifiability and unforgeability security requirements. In some conditions, it may be necessary to protect the proxy signer’s privacy from outsiders or third parties. Recently, several studies about proxy signature schemes have been conducted but only Yu et al.’ anonymous proxy signature scheme proposed in 2009 attempting to protect the proxy signer’s privacy from outsiders. They claimed their scheme can make the proxy signer anonymous. However, based on our research, we determined that this was not the case and the proxy signer’s privacy was not anonymous. Hence, in this paper, we propose a new anonymous proxy signature scheme that truly makes the proxy signer anonymous while making it more secure and efficient when compared with Yu et al.’s scheme in 2009. Our proxy signature scheme consists of two constructions. First, we mainly use random numbers and bilinear pairings to attain the anonymous property in our proxy. Secondly, we increase the security, integrity, and efficiency of our proxy through modifications

Nominative Proxy Signature Schemes

In a nominative proxy signature scheme, an original singer delegates his signing power to a proxy, who generates a nominative signature on behalf of the original signer. In a nominative proxy signature scheme, only the nominee can verify the signature and if necessary, only the nominee can prove its validity to the third party. In this paper, we first classify the nominative proxy signature into two types, original-nominative proxy signature and proxy-nominative proxy signature. Then we analyze the nominative proxy scheme proposed by Park and Lee. We show that the scheme suffers from universal verification. We also point out that the scheme presented by S.-H. Seo and S.-H. Lee is insecure and the scheme cannot provide non-repudiation. Finally we present our nominative proxy signature schemes which overcome the weakness mentioned above. Compared with the scheme recently proposed by G.-L. Wang, our scheme is more efficient

On the Security of a Proxy Blind Signature Scheme over Braid Groups

A proxy blind signature scheme is the combination of proxy signature and blind signature scheme. In 2009,Verma proposed a proxy blind signature scheme over braid groups. Verma claimed that the proposed scheme is secure against all possible security lapses and also satisfy all essential security attributes.This paper analyzes Verma’s proposed scheme and found that this scheme suffers with the serious security vulnerabilities. This paper show that the proposed scheme does not satisfy unforgeability and unlinkability, which are two essential security requirement of a secure proxy blind signature scheme

Secure Proxy Signature Schemes for Delegation of Signing Rights

A proxy signature scheme permits an entity to delegate its signing rights to another entity. These schemes have been suggested for use in numerous applications, particularly in distributed computing. But to date, no proxy signature schemes with guaranteed security have been proposed; no precise definitions or proofs of security have been provided for such schemes. In this paper, we formalize a notion of security for proxy signature schemes and present provably-secure schemes. We analyze the security of the well-known delegation-by-certificate scheme and show that after some slight but important modifications, the resulting scheme is secure, assuming the underlying standard signature scheme is secure. We then show that employment of the recently introduced aggregate signature schemes permits bandwidth and computational savings. Finally, we analyze the proxy signature scheme of Kim, Park and Won, which offers important performance benefits. We propose modifications to this scheme that preserve its efficiency, and yield a proxy signature scheme that is provably secure in the random-oracle model, under the discrete-logarithm assumption