[[alternative]]The Design of Proxy Group-Oriented Signature Schemes with Anonymous Proxy Agent

計畫編號：NSC92-2213-E032-019研究期間：200308~200407研究經費：416,000[[sponsorship]]行政院國家科學委員

[[alternative]]The Desing of Threshold Proxy Threshold Signature Schemes

計畫編號：NSC91-2213-E032-014研究期間：200208~200307研究經費：384,000[[sponsorship]]行政院國家科學委員

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

[[alternative]]The Design of Group-Oriented Proxy Signature Schemes and Proxy Authenticated Encryption Shcemes (II)

計畫編號：NSC90-2213-E032-025研究期間：200108~200207研究經費：318,000[[sponsorship]]行政院國家科學委員

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

[[alternative]]The Design of Group-Oriented Proxy Signature Schemes with Anonymous Proxy Group

計畫編號：NSC93-2213-E032-020研究期間：200408~200507研究經費：428,000[[abstract]]Mambo 等學者在1996 年，首次提出了代理簽章的概念。在代理簽章法 中，原始簽章者，能委託一個代理簽章者為其產生代理簽章。因應實際群 體導向應用的需求，產生了多人授權代理簽章法、代理多人簽章法、多人 授權多人代理簽章法、門檻式代理簽章法與門檻式代理門檻式簽章法。在 已知的提出的代理簽章法中，有一種代理方式是：原始簽章者可以指明代 理人的身份，並委託他作為代理者。但是，在許多商業交易或軍事機密上 的需求，希望代理簽章者的身份是匿名的，只有原始簽章者才能知道代理 簽章的身份。然而在已知的提出的代理簽章法中，代理簽章者的身份是匿 名時，會產生了下列問題，如果代理簽章者希望匿名，會面臨被原始簽章 者偽造代理簽章的風險：如果不希望被原始簽章者偽造代理簽章，他勢必 公開自己的身份。因此我們在今年度正進行的研究計畫中，研究如何設計 匿名的多人授權代理簽章法，以及匿名的門檻式授權代理簽章法，讓代理 簽章者既可以匿名，也可以不怕被原始簽章者偽造代理簽章。延續本年度 的研究，我們發現當代理簽章者變成一個代理簽章群時，再防止代理簽章 群上面需要更近一步地研究設計。因此本次計畫將繼續探討當代理簽章者 為一代理簽章群時的主題，藉以設計匿名的多人代理簽章法，以及匿名的 門檻式代理簽章法。[[sponsorship]]行政院國家科學委員

A new proxy signature scheme as secure as EIGamal signature

Proxy signature helps the proxy signer to sign messages on behalf of the original signer. It is very useful when the original signer (e.g. the president of a company) is not available to sign a specific document. If the original signer can not forge valid proxy signatures through impersonating the proxy signer, it will be robust in a virtual environment; thus the original signer can not shift any illegal action initiated by herself to the proxy signer. In this paper, we propose a new proxy signature scheme. The new scheme can prevent the original signer from impersonating the proxy signer to sign messages. The proposed scheme is based on the regular ElGamal signature. In addition, the fair privacy of the proxy signer is maintained. That means, the privacy of the proxy signer is preserved; and the privacy can be revealed when it is necessary

A New Proxy Signature Scheme As Secure As ElGamal Signature

Proxy signature helps the proxy signer to sign messages on behalf of the original signer. It is very useful when the original signer (e.g. the president of a company) is not available to sign a specific document. If the original signer can not forge valid proxy signatures through impersonating the proxy signer, it will be robust in a virtual environment; thus the original signer can not shift any illegal action initiated by herself to the proxy signer. In this paper, we propose a new proxy signature scheme. The new scheme can prevent the original signer from impersonating the proxy signer to sign messages. The proposed scheme is based on the regular ElGamal signature. In addition, the fair privacy of the proxy signer is maintained. That means, the privacy of the proxy signer is preserved; and the privacy can be revealed when it is necessary