鑒於網際網路之普及與智慧財產權意識高漲，數位浮水印技術在近年來受到學術及產業界廣泛的注意，其可應用在多媒體資料如數位音樂、靜態影像、動態視訊等，浮水印的技術是將一些數位信號附於各多媒體資料當中，且其具不易破解、不易消除的特性，對於著作權保護問題提供有效的解決方法。
浮水印的加入，無可避免的必定會對影像造成某種程度的影響。因此強韌度與影像品質之間的拿捏就必須依使用者根據需求而定。浮水印技術主要著重於兩個領域，即 Spatial Domain與Frequency Domain 兩部分，各有其應用之領域。

目前浮水印技術多半用於提供資料所有者之所有權認證，但在新型態犯罪手法日漸增多前提之下，浮水印強韌度不再是唯一考量。接收端如何確保資料來源正確性及完整性、如何預防多重浮水印所造成的所有權之模糊等都是目前資訊安全所會面臨的問題。再此一趨勢之下，浮水印之發展結合安全性相關演算法將日漸迫切。數位簽章(digital signature)及時間戳記(timestamp)目前已廣泛的被應用在電子商務等相關領域，但是數位媒體極易遭到不法人士利用各種技術加以竄改，這使得合法使用者簽章很容易遭到破壞，因此如何克服此一問題是數位簽章應用在多媒體資料之一大課題。

本論文計劃在凌波頻譜上結合加密演算法(Encryption)及時間戳記(Time Stamp)並分別於Spatial Domain 與 Frequency Domain 加入浮水印。此一方法除浮水印本身強韌性(robustness)之考量外，也著重於傳送端及接收端驗證之機制。另外使用有意義之浮水印取代以往常用之任意序列(random sequence)浮水印更加深浮水印本身之可辨認性及預防IBM攻擊。

Digital watermarks have been proposed recently as a means for copyright protection of multimedia data. In this paper we emphasize that security of an image.
A timestamp can record the original message’s digest and authentication time to prove the ownership of the original message. This is already used widely in many applications. In this paper we combined timestamp and encryption algorithm such as ECC for watermark embedding to prevent some attack like multi-watermarks and IBM attack. Besides this we also used adaptive block wavelet transform to search the significant coefficients in the LL band in order to increase watermark robustness.

Experimental result shows the watermark extraction after attacks like JPEG compression, noise corruption, cropping and edge sharpening. We also show a watermark that extracted with illegal timestamp or key.

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