「富含訊息多媒體」 – 一種普及溝通之新工具

Abstract

隨著資訊科技的進步，越來越多的裝置被設計出來跟周遭的環境互動，以做各種普及溝通之應用。普及溝通是指人們可以和生活周遭的物體於任何地點與時間做資訊交換；而存在於生活周遭的許多物體可用來容納資訊，達到普及溝通的目的。本論文定義「富含訊息多媒體」，並探討以這種多媒體做普及溝通的方法。 此外，資訊隱藏可將訊息嵌入多媒體中，因此資訊隱藏為達到普及溝通的其一重要技術。然而，目前大部分的數位裝置，如智慧型手機與平板，並不能感知周遭環境的內容，意即他們不能瞭解周遭環境所含有的資訊，因此需要嶄新之資訊隱藏技術，以應用這些裝置和多種不同的富含訊息多媒體做溝通，達到普及溝通之目的。本論文提出了五種富含訊息的多媒體，包含：大張影像、加密影像、文字形式之協作文件，以及特別設計之兩種影像的硬刻版本，並提出對應於此五種富含訊息多媒體的新資訊隱藏方法。 首先，本論文提出一種可將一秘密影像隱藏於任一同樣大小之目標影像之中的資訊隱藏方法。本方法利用色彩轉換技術，建立一「可視秘密碎片馬賽克影像」，該影像看起來類似使用者挑選的目標影像，可將秘密影像隱藏起來成為一馬賽克影像，此種馬賽克影像不僅可有傳輸秘密影像之功能，更解決了傳統資訊隱藏方法無法於影像中嵌入大量資訊的問題。接著，針對加密影像，本論文利用兩次影像加密及空間相關性之比對技術來隱藏資訊，對每一區塊畫素的幾個LSBs做加密達到嵌入一位元資訊的作用。此方法解決了先前已發表兩個技術會遭遇到的平滑影像問題。 除了影像以外，本論文亦提出一可於協作平台隱藏資訊的新方法。此方法能根據秘密訊息產生擬造的修訂歷史，並將秘密訊息隱藏於模擬過程之中。能達此作用，主要是利用多人協作的幾個特性來隱藏資訊，包含：每個修訂版本的作者、被更改文字序列的數量、被更改文字序列的內涵、取代被更改文字序列的文字序列。此外，還利用一下載的XML格式之英文版維基百科來建置模擬多人協作之資料庫。此一所提方法提供了一種利用協作平台進行秘密通訊與安全保存秘密訊息之應用。 最後，本研究另外提出了可從事「自動識別與資料抓取」之兩種資訊隱藏方法，讓普及溝通實現於特別設計之兩種影像的硬刻版本上。此兩種影像之第一種為富含訊息之字元影像，第二種為富含訊息之編碼影像，這些影像可列印於紙上或顯示於螢幕或電視上。詳言之，富含訊息之字元影像其建立方式是先將字元訊息切碎，再產生跟目標影像一樣大的字元影像，接著利用一區塊亮度調變方法來改變字元影像每塊碎片的亮度值，最後將調變之位元影像注入於目標影像之中。而富含訊息之編碼影像其建立方式是先將一訊息轉換為一由二元圖樣區塊所組成的圖樣影像，並同樣透過區塊亮度調變方法，改變每塊圖樣區塊的亮度值，最後將調變之圖樣影像注入於目標影像之中。這兩種影像擁有類似條碼及QR碼的功能，且其外觀看起來類似一任一選擇的目標影像，故可達到普及溝通的效果。 以上所提出的方法皆為創新之作，深入的理論分析及實驗結果顯示這些方法皆具有可行性及實用性。

With the advance of information technologies, more and more devices are designed to interact with environments for various pervasive communication applications; thereby people can exchange information with the identities existing in the environment everywhere and anytime. Many kinds of identities exist in the environment can be utilized to accommodate information for the purpose of pervasive communication. In this study, identities called message-rich multimedia are defined and investigated for pervasive computing. Data hiding can be employed to embed message information into multimedia existing in various application environments, creating message-rich multimedia as the result; therefore, data hiding is regarded as one of the key techniques to achieve pervasive communication. In addition, most existing digital devices like smart phones and tablets are “unaware” of the environment context, i.e., they cannot “understand” the environmental surrounds even if they can “see” them by image taking with the built-in cameras. Therefore, numerous possibilities for achieving pervasive computing through uses of these devices by data hiding techniques via various message-rich multimedia are worth investigation. In this dissertation study, five types of message-rich multimedia are proposed, including: 1) image with large data volumes; 2) encrypted image; 3) text-typed collaborative writing work; and 4) hard copies of two types of specially-designed images; and five new data hiding techniques creating respectively these types of message-rich multimedia are designed. Firstly, a new large-volume data hiding method for hiding a secret image into any target image of the same size is proposed. The method creates automatically from an arbitrarily-selected target image a so-called secret-fragment-visible mosaic image as a disguise of the given secret image. Based on color transformation, the method not only creates mosaic images useful for secure image communication, but also provides a new way to solve the difficulty of hiding secret images with huge data volumes into target images. Next, via encrypted images, a new data hiding method based on the techniques of double image encryption and spatial correlation comparison is proposed as well, solving a problem encountered by two previously-proposed methods when dealing with flat cover images. Specifically, the proposed method encrypts the LSBs of each block pixel in a given encrypted image to embed a message bit. In addition to dealing with images, a new data hiding method via collaboratively-written articles with camouflaged revision history records for use on collaborative writing platforms is proposed. Characteristics of article revisions are identified subtlely and used to embed secret messages, including the author of each revision, the number of corrected word sequences, the content of the corrected word sequences, and the word sequences replacing the corrected ones. An English Wikipedia XML dump is utilized to construct a database for forging the revisions by data hiding techniques. The proposed method is useful for covert communication or secure keeping of secret messages via collaborative writing platforms. Finally, two other data hiding techniques for automatic identification and data capture applications are proposed to enable pervasive communication via hard copies of two types of specially-created images, where the first type is message-rich character image and the second message-rich code image. These image copies may be printed versions on papers or displayed versions on monitors or TVs. Specifically, a digital message-rich character image is created from an arbitrarily-selected target image for use as a carrier of a given message by fragmenting the shapes of the composing characters of the message and injecting the resulting character fragments randomly into the target image by a block luminance modulation scheme. And a message-rich code image is created by converting a given message into a pattern image composed of binary pattern blocks and injecting the resulting pattern image into the target image by a block luminance modulation scheme. With functions similar to those of barcodes or QR codes, the created two types of message-rich images look similar to the target image, achieving the effect of pervasive communication. The feasibility and effectiveness of all the proposed methods are demonstrated by theoretical analyses and good experimental results.