可列印式的資訊隱藏與數位浮水印之技術

Abstract

越來越多學者投入於研究資訊隱藏的技術，因此有很多新的應用被提出。根據這些提出的應用，資訊隱藏可以區分為兩大類:隱藏學與浮水印。隱藏學是一種藉由隱藏機密資訊於掩護媒體內，使得可以進行機密通訊的技術。浮水印則是隱藏一個使用者所定義的圖騰至媒體內，因此，可用該圖騰對此媒體做版權保護或認證。在本論文中，將針對這兩類資訊隱藏的技術，分別提出可列印式的隱藏學與數位浮水印之技術。 首先，本論文要提出的是一個以完美迷宮做為載體的隱藏學方法。隱藏機密資訊於迷宮的想法，最先是由Niwayama等人所提出的。而他們的方法主要有兩個缺點，第一個缺點是藏量很少，另一個缺點是隱藏機密資訊後的迷宮不是完美迷宮。針對這些缺點，我們提出一個高藏量且藏完資訊後依舊為完美迷宮的隱藏學方法。此外，本論文提出的方法所產生的迷宮，當被印至紙上時，該隱藏的機密資訊依舊可以被取出。 本論文第二個要提出的方法是在半色調影像上的浮水印技術。該技術利用縮減取樣頻率及抖色矩陣的特性，使該方法能抵擋裁切、竄改，及列印掃描等攻擊。比較本論文提出的技術與Guo等人的方法，本論文提出技術有高的強韌性，並在影像的高頻的區域上，有較高的視覺品質。

Data hiding techniques have attracted the attention of many researchers, and many applications have been proposed. According to the applications, data hiding techniques can be divided into two categories: steganography and watermarking. Steganography is a technique to build a secret communication channel by embedding secret messages into cover media. Watermarking is a technique to embed a watermark into a media for copyright protection and authentication. In this dissertation, two printable data hiding methods are proposed. First, a perfect maze based steganographic method is proposed. The original idea of embedding data in a maze was presented by Niwayama et al. Their method has two disadvantages. One is very small embedding capacity; the other is that the embedded maze is not perfect. To treat these disadvantages, here, the proposed method will provide higher embedding capacity and preserve the “perfect” property. In addition, when a stego maze is printed on a paper, the secret messages can still be extracted. Next, a robust watermarking method for dithering halftone images is provided. Based on downsampling and the property of a dispersed dithering screen, the method can resist cropping, tampering, and print-and-scan process attacks. In addition, comparing to Guo. et al.’s method, the experimental results show that the proposed method provides higher robustness for the above mentioned attacks and better visual quality in the high frequency regions of halftone images.