使用視覺上可移除的浮水印實現可調式多媒體階層式保護

Abstract

隨著網際網路的日漸普及，數位資料變得非常容易取得，因此我們需要一個保護架構來保護智財權。再者，由於行動通訊的發達，加上行動通訊本身頻寬的多樣化，造成了可調式多媒體日趨重要，如此一來，為了保護可調式多媒體，一個可調式多媒體階層式保護的架構被提了出來。這個架構利用加密系統來保護各階層的資料，而解密的金鑰則以浮水印鑲嵌在上一個階層的資料內。 在本論文中，我們主要的目的是驗證可調式多媒體階層式保護的可行性，其驗證的範圍包括了解析度可調以及影像品質可調。為了驗證這兩種可調式媒體，JPEG2000被選擇為測試平台，這是因為JPEG2000本身提供了解析度可調與影像品質可調的檔案格式。為了攜帶解密金鑰，一個視覺上可移除的數位浮水印被設計出來，這個數位浮水印利用鑲嵌高強度的浮水印來達到高資料容量的目的，但是隨之而來的是一個品質較差的鑲嵌後影像，不過一個視覺上不受影響的影像可以在最後被取得。有了視覺上可移除的數位浮水印的幫助，用來保護解析度可調或是影像品質可調多媒體的階層式保護架構可以被完整地實現。

With the widespread use of Internet, digital multimedia data are easy to access. Therefore, a protection scheme is needed to secure the intellectual property. On the other hand, scalable media coding becomes more and more important due to the varying bandwidth in transmission such as mobile communication. Hence, a layered protection scheme of scalable media was proposed. It is a scheme which protects data of each layer by cryptosystem and the decoding key of the current layer is carried by the watermark embedded in the previous layer. In this thesis, our goal is to design and implement the layered protection scheme for the SNR and the spatial scalable media. Thus, the JPEG2000 still image compression standard, which provides content formats for SNR and spatial scalabilities, is used as the platform in our implementation. To fulfill all the requirements in our system, the perceptually removable watermarking (PRW) is chosen for carrying the decoding keys. The specifically designed PRW embeds the watermark with high intensity to increase the data capacity, and it can be removed at the other end with virtually no loss on image quality. With the aid of the PRW, the layered protection scheme for SNR and spatial scalability can be successfully implemented.