臺灣博碩士論文加值系統

在公開金鑰加解密系統中，公開金鑰的驗證對於加密資料的安全性而言是不可缺的議題。而X.509公開金鑰基礎建設標準是目前廣泛使用的解決方式。X.509標準定義了在公開金鑰基礎建設中驗證公開金鑰相關的資料格式與運作流程，它是透過一份帶有憑證中心數位簽章的電子憑證來證明公開金鑰的有效性。然而，對於一般使用者來說，很難由憑證內容上所呈現的文字與亂碼數字直接對應想像到公開金鑰擁有者的真實身分。為了解決這個使用上的瑕疵，這篇論文提出了一種產生圖像化憑證的架構。該架構首先將憑證內容的欄位資料依照辨識方式區分為『使用者認證』與『程式驗證』兩大類。不同於傳統憑證，圖像化憑證以圖形化資料如照片、商標、記號等等來表達『使用者認證』欄位資料讓使用者能清楚分辨。此外，考慮到方便性，該架構利用可視與不可視浮水印技術將憑證內容所包含的各個欄位資料整合到一張公開金鑰擁有者的代表照片，使圖像化憑證能以一般電子影像格式呈現憑證內容。這種新型態的圖形化憑證稱為『照片式憑證』。我們以目前常用的影像格式Bitmap來實作這個架構以證明該架構是可行的。

In public-key cryptography, the authentication of public keys is an essential topic for securing electronic data. The X.509 certification authority-based (CA) public key infrastructure (PKI) standard is a widespread solution which explicitly defines data formats and procedures related to the authentication of public key via public key certificates that are digitally sighed by CA. However, the formats of X.509 certificate contents, which consist of randomized integers and string data, are not friendly enough for human to directly associate the identities of real persons. To overcome this drawback, this thesis presents a framework for generating a kind of visualized certificate in image formats. We name this certificate as “photo certificate”. The fields of a certificate are classified into user identification data and program identification data according to their usage. Instead of describing in string data, photo certificate expresses user identification data by a visualized presentation form such as photos, logos, marks, etc. Furthermore, it utilizes watermarking technique for integrating user identification data and program identification data into an image format. We will implement photo certificate in bitmap format to prove that this framework is feasible.

Acknowledgements i
中文摘要 ii
Abstracts iii
Table of Contents iv
List of Figures v
List of Tables vi
Chapter 1 Introduction 1
1.1 Related Knowledge of Public Key Authentication 1
1.1.1 Public-key Infrastructure 2
1.1.2 X.509 Certificate 3
1.2 Motivations 5
Chapter 2 Visualized Certificate 7
Chapter 3 Brief Introduction of Data Hiding 9
3.1 Steganography 10
3.2 Watermarking 10
Chapter 4 Proposed Framework 11
4.1 Preliminary Work 11
4.1.1 Data Classification 11
4.1.2 Format Transformation 12
4.2 Generation Phase 13
4.3 Verification Phase 15
4.4 Implementation 16
4.5 Discussion 19
Chapter 5 Conclusions and Future Works 22
References 23

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