當網路和貯存設備變得越來越普及時，數位資料越容易且越快速的被散佈。盜版者可以輕易且沒限制的複製大量多媒體資料(圖像，音訊和視訊)。因此，人們越來越關心多媒體智慧財產權的保護。

數位浮水印是一個有用且正在發展中的技術，它是一種直接在原資料中嵌入額外資訊的技術。理想上，被加入數位浮水印的資料應該和原資料沒有視覺上的差別，而且數位浮水印不可以在受保護資料沒有受損害的情形下輕易的被移除或修改。數位浮水印的應用包括版權的保護，版權擁有者的認證，以及廣播監視。數位浮水印和傳統的密碼保護最大不同在於受密碼保護的資料在經過解碼後就沒有保護的功能了，這些解碼後的資料可以被複製且散布。相對的，受數位浮水印保護的資料不論在什麼情況下，只要遇到有版權的問題時就可以利用浮水印技術從受保護資料中抽取出藏入的資訊，進而解決版權的爭議。

近幾年有越來越多的研究在討論如何把數位浮水印嵌入影像當中。在影像浮水印系統中，通常把數位浮水印嵌入在空間域或頻率域裡。在空間域可以利用影像強度的改變嵌入浮水印，而在頻率域則可以利用修改轉換係數來嵌入數位浮水印。在空間域常常把數位浮水印嵌入在較低位元的地方，使影像在視覺上察覺不出變化。相對於影像浮水印系統，較少學者在研究視訊浮水印。視訊浮水印主要有兩個方法被考慮，一個是把浮水印嵌入在未經過編碼的視訊中，另一個方法則是把浮水印嵌入在編碼後的資料串當中，例如移動向量。數位資料常常遭受一些故意或非故意的攻擊，例如壓縮，剪裁，增加雜訊，和幾何攻擊等等。因此，在設計浮水印系統時必須把遭受攻擊的情形考慮進去。

在本篇論文中，我們提出了一個基於方塊演算法的視訊浮水印系統。我們的系統優點是不論遇到故意或非故意的攻擊都有非常高的強韌性。浮水印是嵌入在未經壓縮的視訊資料中，並且在萃取時不需要原本的視訊資料。我們的系統可以經由調整臨界參數，獲得不可視性和強韌性中最佳的平衡。基於安全的理由，浮水印在嵌入的時候會伴隨產生私密安全金鑰。最後的實驗結果將會證實我們的系統在資料遭受多種攻擊後還可以準確的萃取出藏入的浮水印。

As the internet and storage equipment become more and more popular, the digital data can be distributed easier and faster. The pirates can easily and unlimitedly copy the digital multimedia (images,audio, and video). Therefore, people are more and more attentive to the copyright protection for digital multimedia.

Digital watermarking is a useful and developing technology, it is the direct embedding of additional information into the original content or host signal. Ideally, there should be imperceptible difference between the watermarked and original signal, and the watermark should be difficult to remove or alter without damaging
the host signal. In some instances, the amount of information that can be hidden and detected reliably is important. Applications include copyright protection, owner identification, and broadcast monitoring. The evident difference between the watermarking and encryption is that the data is only protected during the transmission using the traditional cryptography. After decrypting, the digital data is no longer protected, it can still be copied and
distributed. In contrast to traditional cryptography, anyone can use the multimedia data, once the dispute about the ownership of data happened, we can extract the information from the host data to authenticate and characterize the owner by watermarking technique.

A lot of researches discussed how to embed a watermark into image in recent years. For digital watermarking of image, it often embedded in the spatial/frequency domain. Watermark can be embedded into the image intensity in spatial domain or into image coefficients in transformed domain. In spatial domain, watermark is usually embedded
into low bits to make it imperceptible. In transformed domain, the image is first orthogonally transformed, then watermark is embedded into transformed coefficients. However, few researches analyzed the watermark techniques in video. As far as the watermarking of a video sequence is concerned, in the literature two approaches are
considered: watermark insertion on the original raw video data or alternatively on the coded data bit stream such as motion vector. Digital content often suffer some intentional or unintentional attacks such as compression, cropping, add noise, and geometric attack, etc. Therefore, we need to consider those of attacks for
designing the watermarking system.

In this thesis, we propose a watermarking system based on block matching algorithm. The advantages of our proposed system are not only the robustness in the signal attack and invisibility but also the robustness in the intentional attack such as cropping. The watermark is mainly embedded in the uncompressed domain, and it is detected without the use of the original video information. Hence, this scheme is powerful and possesses the adjustable threshold value
to obtain the balance relationships between the imperceptibility and robustness. For the security viewpoint, the watermark embedding usually requires the knowledge of a secret embedding key to perform. The experimental results show that our proposed method can
successfully detect the watermark from the attacked video especially for video compression.

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