基於PNG影像之資訊隱藏技術及其應用之研究

Abstract

由於網路的發達及其方便性，數位影像傳輸也隨之變得頻繁，其中PNG影像是當今應用相當廣泛的一種影像格式。在本論文中，我們針對PNG影像提出了幾種資訊隱藏的技術與應用，包括版權保護、秘密分享及秘密傳輸。在版權保護部份，我們提出一個基於固定大小區塊的影像驗證方法，讓我們調整影像中紅綠藍色及透明通道的像素值，使其符合某種限制條件，來作為驗證訊號，並用以驗證影像之真假性及完整性。在秘密分享方面，我們提出一種藉由解聯立方程式來達到秘密分享效果之方法，該法由n 讣汹1張使用者自選的掩護影像(cover image)產生n份分享檔案，並且將這n份分享檔案藏進掩護影像的透明通道中，形成n份偽裝影像(stego-image)。我們可以藉由收集n張偽裝影像中的分享檔案來復原原本的秘密。在秘密傳輸部分，我們根據以上提到的驗證和秘密分享之技術提出了兩種資訊隱藏的方法。另外，我們亦結合驗證和資訊隱藏，提出一種可驗證秘密資訊之方法。最後，我們以實驗結果證明了所提方法之可行性。

With the convenience and fast speed on the Internet, exchanges of multimedia become more and more frequent nowadays. PNG images are used in a wide variety of applications. In this study, we propose several methods for data hiding applications via PNG images, including copyright protection, secret sharing, and covert communication. For copyright protection, we propose a block-based method for file authentication, which can authenticate the integrity and fidelity of PNG images by adjusting pixel values to meet some constraints in the three color channels (red, green, and blue) and the alpha channel. For secret sharing, we propose a method by solving three simultaneous equations to generate n shares from n 讣汹轨 cover images, and embedding the shares in the alpha channels of the color images. We can recover the secret by collecting all the shares. For covert communication, we propose two data hiding methods which are based on the proposed authentication method and the proposed secret sharing method. We also apply the two methods to yield a combined data hiding and authentication method to authenticate hidden data. Good experimental results show the feasibility of the proposed methods.