利用WebM視訊做資訊隱藏及其應用之研究

Abstract

隨著網路以及視訊壓縮技術的進步，數位影片已經成為我們生活中的一部分。WebM是Google 公司所開放免版權費用的開源視訊格式，WebM針對影片在網路上的使用做最佳化。本論文針對WebM影片利用資訊隱藏技術做秘密傳輸、視訊驗證及隱私權保護之研究與應用。在秘密傳輸部份，我們提出了一個修改頻率域係數嵌入秘密訊息的方法，不但考慮到秘密訊息的可藏量以及影片嵌入後的品質，也考慮到秘密訊息安全性的問題。在視訊驗證方面，因為視訊監控影片經常成為不法使用者竄改掩蓋犯罪事實的對象，所以我們利用資訊隱藏技術及WebM特性，提出一個偵測移動物體作為驗證訊號的方法，對可能遭受竄改的影片做驗證。在隱私權保護部份，因為視訊監控影片經常在個人隱私權方面引起爭議，所以我們提出了一個使用WebM特性將具有隱私爭議的影片內容消除及復原的方法。最後我們提出了相關的實驗結果，證明我們所提的方法是可行的。

With the advance of the Internet and video compression technologies, uses of digital videos nowadays have become part of the human life. WebM is one of the video coding standards developed in recent years, which has many merits, such as its openness offered by Google, Inc., optimality for uses on the web, etc. In this study, methods for three data hiding applications, namely, covert communication, video authentication, and privacy protection, are proposed using WebM videos as cover media. For covert communication, a data hiding method via WebM videos by frequency coefficient modifications in the frequency domain is proposed. The method considers not only the data hiding capacity and imperceptibility, but also the security issue. For video authentication, a method which detects motion objects in a surveillance video to generate authentication signals and embed them in the video to yield a protected version is proposed. The proposed method may be used to verify possible tampering attacks in the protected surveillance video. For privacy protection in videos, a method for removing privacy-sensitive contents from a video by using WebM features and embedding the removed contents in the same video imperceptibly is proposed. The hidden privacy-sensitive contents can be extracted later to recover the original privacy-sensitive contents. Good experimental results show the feasibility of the proposed methods for applications on covert communication, video authentication, and privacy protection in videos.