臺灣博碩士論文加值系統

隨著行動商務的日漸普及，我們發展了很多的應用程式，某部份的應用程式是設計來傳送電子資訊，例如新聞傳播、視訊會議。Multicast 是主要的傳送方式 ,當Multicast傳輸時,我們必須管理群組鑰，必要的時候我們會進行群組鑰的更新動作來保護我們的資訊內容，這個動作稱之為 re-keying 。然而，太多的 re-keying 動作將會耗費過多電腦的運算能力以及頻寬，因此如何減少 re-keying 次數已經成為一個很熱門的研究方向。在使用者轉換群組時網路上管理key的伺服器會使用Multi-group key管理方法來進行re-keying，利用這個方法來管理key可以省下很多re-keying次數，因為大部分的key 可以在使用者端自動產生，但是為了符合 forward security 和 backward security 這兩個安全需求，有些部驟一樣要採用傳統的re-keying方式，因此我們的目標是要設計一個管理key的機制，可以使re-keying次數最小化。過程中我們利用一個存取控制多項式來改善Multi-group key管理方法的管理過程，並且將我們所提出的存取控制多項式進行最佳化 , 以改善伺服器和使用者端處理的效率，最後我們比較Multi-group和我們提出的方法,我們發現我們提出的方法有比較卓越的效率和較少的re-keying次數。

With the m-commerce becomes more and more common and many applications have been developed. Some of them are designed for information content delivery, such as news push, teleconference. Multicast is the main delivery way. In the process of multicast, we need to manage the group key and do some re-keying actions to protect the information content. However, too many re-keying actions would cost lots of computing capability and network bandwidth, so how to decrease the re-keying times becomes a hot issue. When nodes switch among groups, the key server would update keys by adopting the Multi-group key management scheme. In the re-keying steps, some re-keying actions can be done automatically by nodes. But for the security requirements of forward and backward security, we still adopt the traditional re-keying actions in the service group of the leaving side.
Hence, we aim to design a key management scheme that can minimize re-keying times. In the process of distributing keys, our proposed key management scheme generates a polynomial string to replace traditional re-keying steps. Furthermore, in order to improve the performance of processing time at server and client, we optimize the process of picking keys when generating polynomial string. After comparing our proposed scheme ACP to Multi-group, we find it has not only fewer re-keying times but also better performance.

1. Introduction 5
1.1 Background 5
1.2 Motivation and Objective 7
2. Related Works 8
2.1 Logical Key Hierarchy Tree (LKH) 8
2.1.1 Joining and Leaving the Group 11
2.1.2 Switching Service Group 14
2.2 User’s Privileges and Resource Hierarchy 16
2.3 The Existing Group Key Management Schemes of LKH 17
2.4 Access Control Polynomial (ACP) 18
3. Proposed Hierarchical Key Management Scheme 20
3.1 Preliminaries 20
3.2 The Switch Action in LKH with Access Control Polynomial (ACP) 22
3.3 To Optimize the Access Control Polynomial 24
4. Performance Analysis and Comparison 25
4.1 Simulation Implementation 25
4.2 Rekey Overhead Analysis 27
4.3 Performance Comparison 29
5. Conclusion and Discussion 32
References 33

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