具時限的代理簽章系統

Abstract

原始簽章者可以利用代理簽章系統將他的簽章權限授權給一位合法的代理簽章者，在得到授權之後，代理簽章者便可以代為執行原始簽章者的簽章程序，並產生合法的代理簽章。在這篇論文中，我們首先提出一個根基於GQ簽章系統的代理簽章系統，這個系統符合了代理簽章系統所必須滿足的所有強條件要求，而且我們可以證明它的安全性。 我們提出了具有時間限制的代理簽章系統的概念，並進一步地提出一個具體的具時限的代理簽章系統，在這個系統裡所產生的代理秘密金鑰本身就具有代理簽章時間的限制。於是一位合法的代理簽章者只能在合法的時間內代為執行原始簽章者的簽章程序，在合法時間外所簽出來的代理簽章將被驗證程序檢查為不合法。

Proxy signature is a signature scheme that is designed to delegate the original signer’s signing capability to a designated proxy signer. Then the proxy signer creates a proxy signature on behalf of the original signer. In this thesis, we proposed a new proxy signature scheme that is based on the GQ signature scheme. The proposed scheme satisfies all strong condition requirements and was proved to be secure. Furthermore, we introduced the concept of time bounded proxy signature schemes and proposed a concrete time bounded proxy signature scheme where generated proxy secret key has its inherently effective time periods. “Time Bounded” means that the proxy signer can only sign a message for periods permitted by the original signer. The proxy signatures created for other periods will be determined to be invalid. Our time bounded scheme also satisfies all strong condition requirements.