數位浮水印是一個可藏匿私密資料至影像之技術，對於一般影像而言，將一像素值輕微地改變並不容易被人眼視覺所發現，因此數位浮水印可以被用來保護影像作者的智財權，成為防止非法盜版的重要機制。近年來浮水印技術開發蓬勃發展，但以嵌入式系統作為平台的應用卻很少見。由於在手持式裝置上電池容量是有限的，如何降低在裝置上執行程式運算時所造成的功率消耗變成了應用程式設計者一項重要的課題。為了實現可應用在嵌入式系統上的浮水印機制，在本論文中，我們提出一個基於直接序列分碼多重存取技術之低功率消耗、高容量與高強健性的浮水印演算法。
在本論文所提出的方法中，多組正交的展延碼被利用來展延多張待嵌入的浮水印影像，並將展延後的浮水印訊號嵌入至頻域係數中。其中，我們以離散餘弦轉換的方式來取得頻域係數。如此一來浮水印演算法所需具備之資料嵌入量、強健性、與安全性等特性可同時獲得提升。此外在降低功率消耗方面，我們根據離散餘弦轉換與直接序列分碼多重存取技術兩者的特性來設計一個低運算複雜度之頻域轉換機制，並將此機制應用於以直接序列分碼多重存取技術為基礎之浮水印嵌入程序。更精確而言，我們提出一個全新的以直接序列分碼多重存取技術為基礎之浮水印嵌入架構。
由實驗結果我們可以清楚地發現，相較於一般傳統基於直接序列分碼多重存取技術之浮水印演算法，所提出的方法可省下82.2%之能量消耗。而在強健度方面，透過進行取出浮水印品質檢測的實驗可知，所提出的浮水印機制即使在JPEG影像壓縮或多種不同的影像處理攻擊下，還是能成功地取出具鑑別度之浮水印影像以成功地保護智財權。

Recently, digital watermarking is an active technique for the copyright protection. Since the battery life of portable device is restricted, reducing the energy consumption in an embedded system is a crucial goal. In order to implement watermarking scheme for embedded systems, we present an energy efficient, secure and robust watermarking algorithm based on DS-CDMA technique in this master thesis.
In this proposed method, multiple watermark patterns are spread with multiple orthogonal spreading codes and then embedded to DCT domain coefficients. In this way, all the capacity, security, and robustness can be improved simultaneously. For power saving, according to the properties of DCT and DS-CDMA technique, we propose a low computational complexity frequency domain transformation for the DS-CDMA embedding. More precisely, we proposed a new architecture for the DS-CDMA based watermarking.
Experimental results show that our approach can reduce 82.2% energy consumption. Moreover, the quality measuring results demonstrate that the proposed DS-CDMA watermarking algorithm is robust enough against several signal distortions such as JPEG compression, sharpening, blurring, intensity adjusting, cropping and random noise adding.

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