傳統的浮水印技術面臨兩個重要的問題。第一，在演算公開的情況下，很難抵擋針對演算法所設計出來的攻擊,這些攻擊可以輕易地抹除已加入的浮水印，第二，一張影像可以同時加入很多浮水印，甲說這是他的影像，乙說這也是他的影像，兩者都可以萃取出浮他們的浮水印，然而我們就無法得知誰這張影像的所有權歸誰所有。這兩個問題，使浮水印的技術無法全面的發展。
數位影像版權保護有別於傳統的浮水印技術，最重的的特點是對於被保護的影像，我們無須修改它。我們只要將影像的特徵取出，然後用萃取出的特徵再向授權的公正的第三者註冊，再完成註冊手續的同時，一個時間戳記被紀錄，用來證明註冊的時間。將來如果對影像的所有權有爭論，第一個註冊的人將被公定為合法的所有權人。
對於影像的特徵的翠取，有很多方法提出來。但很少特徵的翠取方法，在受到各式各樣的攻擊依然保持不變，尤其是受到幾何上的攻擊。我們的方法是基於Mexican Hat Wavelet scale interaction 所萃取出來的特徵點。這種方法萃取出來的特徵點可以抵擋訊號處理攻擊和幾何攻擊。
查此張影像是否已經註過冊，我們就要拿這張影像萃取出來的特徵，再儲存資料庫逐一比對是否吻合。要注意的是，這張影像可能已遭受到攻擊，特徵點可能有些位置上的改變。我們觀察到，這些特徵點有結構性的位移變化，換句話說，特徵點之間的相對位置並沒有明顯的改變。因此在我們提出的方法中，提出一系列的反運算以訂正受到扭曲變化的特徵點。訂正過後，再來比對是否吻合。

Traditional watermark scheme has encountered two serious problems. First, it is easy to attack watermark by methods which are specifically designed for its algorithm. Second, an image may be embedded many watermark simultaneously. We have no ideal which watermark was embedded first which one was embedded latter. Therefore, to determine truly owner of the content becomes impossible.
Digital image copyright protection scheme is very different from traditional watermark. No modification of original image is needed. Only what we should do is extract feature of image and register to the third party with it. At the same time, we get a time stamp to prove at what time we register the content. When argument happened, the first registrant is truly legal owner of the image. The first registrant is defined who has the earliest time stamp.
There are many ways proposed for feature extraction. But seldom feature remains unchanged under various attacks, especially geometric attacks. Our feature extraction method is called Mexican Hat Wavelet scale interaction. The extracted feature points can resist both geometric distortion and signal processing.
Here come the problems about feature points pattern matching when we want to check an image registered or not. We observe that feature points have structural position shift. So our methods applied many inverse transformations to correct its distortion when suffered from attacks.

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