以改進式區塊加密技術應用於可燒錄光碟之全像影像數位浮水印

Abstract

由於電腦資訊科技的突飛猛進，今日電腦的運算能力已非常強大，足以處理許多複雜的數學計算，再加上光碟燒錄器材的普及，近年來有學者利用電腦演算產生全像圖的技術(computer-generated holograms, CGH)將全像圖案燒錄於光碟片上，而光碟導溝以及燒錄點間距之數量級與光波的波長相當，因此當光線照射於光碟片資料面時便會產生彩虹般的繞射現象而形成全像圖案。此外為了提高光碟片多重防偽的效果，亦有學者結合區塊加密技術以及光碟燒錄全像技術將一數位影像經由區塊加密演算法加密後燒錄到光碟片上，再透過光學取像系統將影像擷取並且解出其中的隱藏資訊，且光碟片上之全像圖案無法透過光碟對拷的方式進行複製，因此光碟片本身除了儲存資料外，也藉由本研究技術增加了版權保護的效果。 本研究更將此技術應用於DVD可燒錄光碟片上，由於DVD可燒錄光碟的燒錄密度大於CD-R，因此在固定儲存面積下，DVD可以儲存更多的資料，如此可以增加使用上的彈性。而以往的技術僅針對局部的影像進行加密，經本研究改進後將加密的範圍擴展至整張光碟片上之全像底紋，另外透過調整區塊的高斯分佈以及隨機雜訊之參數，便能使加入的區塊呈現不同的面貌，使得加密過後之光碟片除了具有版權保護的效果外，在視覺上也可以更加美觀。 最後本研究將數位設計稿與拍攝後之影像進行分析，找出兩者間的轉換關係，以提供未來使用者在設計全像影像時更加方便。Today, the personal computing capability is more and more powerful to processes many complex mathematic algorithms and operations, and the desktop CD recorder is a very feasible way to record data. In recent years, some researchers used computer-generate holograms (CGH) and disk recorders to output holographic images on CD-R disk’s data side. Since the disk’s microstructure is equivalent to the wavelength of the visible light, the diffraction holographic image on a CD-R disk can be observed. There are also some scholars combined this technique and the patchwork watermarking technique on CD-R disk’s, and the watermarked holographic image in cd can’t be duplicated by disk-to-disk copy. It can serve on an anti-counterfeiting feature for CD-R. Those techniques are also applied to DVD disk, and it shows that DVD can store more data and display distinct holographic image. In addition, we are not only hide watermark in an image which occupying portion of the disk area, but also hide watermark on the whole area of DVD disk. The patch size and shape on DVD disk are also carefully studied for obtaining both anti-counterfeiting and aesthetic purpose.