[[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

A Novel Blind Signature Scheme Based On Discrete Logarithm Problem With Un-traceability

Blind Signatures are a special type of digital signatures which possess two special properties of blindness and untraceability, which are important for today’s real world applications that require authentication , integrity , security , anonymity and privacy. David Chaum[2] was the first to propose the concept of blind signatures. The scheme's security was based on the difficulty of solving the factoring problem [3, 4]. Two properties that are important for a blind signature scheme in order to be used in various modern applications are blindness and untraceability[2, 5, 6] . Blindness means that the signer is not able to know the contents of the message while signing it, which is achieved by disguising (or blinding) the message through various methods. Untraceability refers to preventing the signer from linking the blinded message it signs to a later unblinded version that it may be called upon to verify. Blind signatures based on discrete logarithm problem are still an area with much scope for research. We aim to propose a novel blind signature scheme with untraceability , based on the discrete logarithm problem

A publicly verifiable quantum signature scheme based on asymmetric quantum cryptography

In 2018, Shi et al. \u27s showed that Kaushik et al.\u27s quantum signature scheme is defective. It suffers from the forgery attack. They further proposed an improvement, trying to avoid the attack. However, after examining we found their improved quantum signature is deniable, because the verifier can impersonate the signer to sign a message. After that, when a dispute occurs, he can argue that the signature was not signed by him. It was from the signer. To overcome the drawback, in this paper, we raise an improvement to make it publicly verifiable and hence more suitable to be applied in real life. After cryptanalysis, we confirm that our improvement not only resist the forgery attack but also is undeniable

A Thesis: A CRYPTOGRAPHIC STUDY OF SOME DIGITAL SIGNATURE SCHEMES.

In this thesis, we propose some directed signature schemes. In addition, we have discussed their applications in different situations. In this thesis, we would like to discuss the security aspects during the design process of the proposed directed digital signature schemes. The security of the most digital signature schemes widely use in practice is based on the two difficult problems, viz; the problem of factoring integers (The RSA scheme) and the problem of finding discrete logarithms over finite fields (The ElGamal scheme). The proposed works in this thesis is divided into seven chapters

[[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

[[alternative]]The Desing of Anonymous Proxy Automatic Signature Schemes for Distributed Compilers

計畫編號：NSC94-2213-E032-022研究期間：200508~200607研究經費：422,000[[abstract]]本計畫預定提出適用於分散式誠實製造編議器的匿名自動代理簽章 法，藉以抵抗(未知)電腦病毒的威脅。由於網際網路的普及，電腦病毒的 危害也變得比以往嚴重。雖然防毒軟體可以提供抵抗電腦病毒的保護，但 是防毒軟體無法偵測未知的電腦病毒。在另外一方面，數位簽章法可以偵 測未知的電腦病毒，因為數位簽章法驗證檔案是否被病毒更動過。利用誠 實製造編議器，日本學者Usuda 等人提出自動簽章法以抵抗電腦病毒，隨 後學者Lin 和Jan 提出他們的適用於分散式誠實製造編議器之自動簽章 法。不幸地Lin 和Jan 的方法不足以抵抗偽造簽章攻擊，另外存在原始程 式碼長度受限的限制。於是學者Hwang 和Li 提出他們的適用於分散式誠 實製造編議器之自動代理簽章法。 在Lin 和Jan 的方法與Hwang 和Li 的 方法中，代理編議器編議工作的伺服器之隱私並未受到保護。為了抵抗編 議器製造者偽造自動簽章攻擊，伺服器之公開金鑰與秘密金鑰並須分別用 於自動代理簽章的驗證與產生，然而維護伺服器之公開金鑰的變更過程是 十分不方便的事。若匿名自動代理簽章只需使用編議器製造者公開金鑰就 可以驗證，不僅可以保護伺服器之隱私，也可以方便匿名自動代理簽章法 的實用性。所以本計畫預定提出適用於分散式誠實製造編議器的匿名自動 代理簽章法。[[sponsorship]]行政院國家科學委員

Critical Perspectives on Provable Security: Fifteen Years of Another Look Papers

We give an overview of our critiques of “proofs” of security and a guide to our papers on the subject that have appeared over the past decade and a half. We also provide numerous additional examples and a few updates and errata