臺灣博碩士論文加值系統

由於通訊網路的普及，電子商務也隨之蓬勃發展。現存已有一種稱為「價格忘卻式傳輸」的傳輸協定，適用於當買家向賣家進行商品交易時，他不願意透漏他購買的商品是什麼，藉以保護自己的隱私。但是，假使有惡意買家在購買後，非法釋出此數位商品，賣家則無法得到保障，因此，此協定已經發展至擁有保護賣家的版權機制，名叫PBSW 協定。我們發現「價格忘卻式傳輸」協定在商品交取的過程中有漏洞，無法確實保護買家的隱私，使買家不能放心進行交易。本篇論文修正「價格忘卻式傳輸」協定的模組，加入取得買賣雙方信任的公正第三方角色來實現能夠保護買家隱私的商品交易。因為原本「價格忘卻式傳輸」協定使用的浮水印機制是嵌入至數位商品中，會降低產品本身品質，我們也修正了浮水印機制，使用視覺密碼加密技術提出一個有效率的新價格忘卻式協定。我們實現了「價格忘卻式傳輸」的定義，重新規劃現有的協定模組，提出「新價格忘卻式傳輸」協定，在實驗過程中，以圖片為交易產品的例子，並使用可視性浮水印機制來測試浮水印的強度，經實驗結果，本研究的浮水印機制強度能夠抵擋大部分的對產品的攻擊。本篇研究有以下兩個貢獻，改善「價格忘卻式傳輸」協定，使買家可以在保護自己隱私的環境中進行交易和 建構秘密分享的產生流程，使之更具實用性。

Because the rapid development of network, the e-commerce also flourishing. There is an existing transaction protocol called Priced Oblivious Transfer (POT). It is applied that when a buyer wants to perform transactions with a seller, he would not disclose what he purchased. But, if there is a malicious buyer release the digital product illegally after buying it, the seller cannot be protected. Therefore, the protocol has been developed to protect the copyright for sellers, it called PBSW protocol. We discovered there are some defects in the POT protocol, when seller send the digital product to buyer, the privacy of buyer might be disclosed. The mechanism is not secure enough for buyer to perform purchase. In this paper, we revised these defects of POT protocol. In order to achieve protecting buyers’ privacy, we add a trust distributor in whole trade model. Because the watermarking technique in PBSW protocol is embedded the watermark into the digital product, the quality of product will be reduced. So, we also change the watermarking mechanism, we utilize the visual cryptography technique and proposed a Revised Priced Oblivious Transfer Protocol (RPOT). Our study achieves the definition in POT protocol by re-planning its model. In our experiment, we take the picture as an example, and utilize Visual Cryptography Technique to test robustness. The result of experiment, our watermarking mechanism is robust enough to resist attacks. The main contributions include the following. First, we improved the POT protocol and let buyers can buy in an environment which is privacy. Second, we conduct the process of generating secret share to make it more practical.

Abstract (In Chinese)........................i
Abstract (In English)........................ii
acknowledgement..............................iii
Content......................................iv
List of Tables...............................v
List of Figures..............................vi
1. Introduction..............................1
2. Preliminaries.............................3
2.1 Digital Watermark........................3
2.2 Visual Cryptography......................5
2.3 k-out-of-N Oblivious Transfer............6
2.4 Priced Oblivious Transfer Protocol.......7
2.5 Weakness of PBSW Protocol................9
3. Proposed RPOT Protocol....................12
3.1 Secret Share Generation Stage............15
3.2 Watermark Extraction Stage...............17
3.3 RPOT Protocol............................17
3.3.1 Initial Phase........................18
3.3.2 Purchase Phase.......................19
3.3.3 Watermark Generation Phase...........20
3.3.4 Arbitration Phase....................21
4. Experiment................................22
4.1 Experimental Design......................23
4.2 Experimental Result......................23
5. Analyze..............................27
5.1 Security Analyze.........................27
5.2 Discussion...............................29
6. Conclusion and Future Work................30
References...................................31

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