摘要
摘要 在本論文中，我們結合公開金匙和秘密金匙密碼系統發展出混合 型密碼系統，以此系統設計兩個符合UMTS安全需求的認證協定， 並且提出了主動認證這個概念。 在我們的研究過程中，我們發現無論是第二代或是第三代行動通 訊系統，只要以挑戰–回應這個機制為基礎來做相互認證就必須使用 三個信號流程。為了改善這個問題，我們提出了主動認證這個構想， 它不但解決了相互認證過程中需三個步驟的問題而且使得整個認證 中不僅做到使用者和網路操作者的相互認證，還有使用者和服務提供 者的相互認證，這種構想在設計新的認證協定和提昇整個認證的安全 上均有莫大的幫助。 我們所提出的兩個新架構除了採用上述的方法還加入了金匙交 換來解決通訊金匙的分配和管理問題，所不同的是，在第一個架構 中除了有使用者和網路操作者間的通訊金匙還有網路操作者和服務 提供者間的秘密金匙。在第二個架構中則是使用者、網路操作者和服 務提供者共用一把鑰匙，這把鑰匙既是秘密鑰匙也是通訊金匙端看在 何處使用，這樣的做法會減少手機的運算量進而加快認證速度。因此 在整篇論文中，我們獲得如下的研究結果﹕﹙一﹚提出主動認證的概 念，﹙二﹚使用混合型密碼系統。
關鍵字
認證協定並列摘要
Abstract This thesis proposes two new frameworks for authentication proto- col for Universal Mobile Telecommunications System (UMTS). The frameworks adopt the public-key cryptography to fulfill the security features required in the third generation (3G) mobile systems. Our new protocols not only improve some weaknesses on the current authenti- cation schemes for the second generation mobile systems, can also apply to another measure for the currently proposed authentication mechanisms in 3G mobile systems. In our study, we use a number of ways such as Timestamp, Digital Signature, Challenge-Response, etc., to authenticate two parties and reduce the procedures of authentication. In addition, our two schemes use the hybrid mechanism that combines the asymmetric and symmetric cryptosystems to overcome the drawbacks of second gen- eration (2G) mobile systems. Furthermore, we propose a concept of active authentication to simplify authentication protocol between users and systems. Our schemes not only achieve requirements of the published protocols but provide the high level of reliability. In the first framework, we use key exchange twice to arrive at trans- port of session key and secret key. Furthermore, the cost of manufacturer and the key management problem are taken into account in our second scheme so that one time key exchange is used in this framework. To sum up, two ideas have been proposed in this thesis to improve the performance of the authentication protocols of UMTS as follows: 1. Active authentication. 2. Hybrid mechanism that combines the asymmetric and symmetric cryptosystems. It is believed that the results of our study in this thesis will be helpful for the future research in the authentication protocol of 3G mobile communication systems.