- 學位論文
高容量與高效率嵌入隱寫術
High-Capacity and Efficient-Embedding Steganography
摘要
網際網路提供了使用者隨時隨地交換訊息，因此資訊安全是重要的議題。有一種技術是專門隱藏重要訊息稱為”隱寫術”，或”資訊隱藏”。資訊隱藏的目的是在已知的公開媒體中嵌入欲傳遞的秘密訊息，或是在多媒體檔案中置入難以移除的浮水印並公開宣稱其擁有權。這類的研究主要訴求於如何提高隱蔽容量並同時降低與原來的宿主檔案的失真度。 我們在這篇論文中提出三個資訊隱藏的方法，其中兩種為盲且可還原。第一種是利用類比調變的原理，我們將欲傳遞的秘密訊息載入超高頻的頻段使其人類聽覺無法知覺然後併入公開媒體音樂，此時，各個頻段的載波是關鍵鑰匙，合法的接收者必須先利用安全通道得知。由於超高頻的頻段無法察覺且無限，因此我們的實驗顯示可以無限制的放入高頻訊號，這使得隱蔽容量的限制提升了。 第二種資訊隱藏方法主要是植基於生理訊號的研究，我們利用錯誤更正碼原理（漢明碼）並在麻省理工學院的公開資料庫中選取樣本進行實驗。錯誤更正碼的原理是植入數個偵測位元來達成訊號糾錯的目的，我們反過來使用，當更改一個位元時可以同時表示隱藏數個位元。這種方法可以增加隱寫術的效率，一般的方法不論是更改時域或頻域的內容，往往最多只能在更改一個位元時嵌入一個位元而已，而我們提出的方法可以在更改一個位元時同時嵌入數個位元。利用錯誤更正碼發展隱寫術的研究中，我們是第一個盲且具可還原性的設計。 第三種資訊隱藏方法主要是由人工合成音樂隱匿資訊。近年來，由於社群媒體的興起，許多使用者會於社群媒體發布自我定義之媒體，這使得發展適於自我定義之媒體隱寫術具有應用性。而自我定義媒體的優勢在於，可於合成期間順勢藏匿秘密訊息達成”合成相似度越高，隱匿訊息越多”的特性。我們的實驗中初步顯示出，可藉由合成的步驟越細膩，不但合成出來的音樂越真實，隱匿的位元數也越高。這是一種為了打破隱寫術過去的瓶頸：隱匿量越高，失真度越高。
並列摘要
The Internet allows people to exchange personal private information and great importance is now attached to data security. Many means of keeping data confidential have been designed. The field of steganography, which is also called “data hiding”, concerns the embedding of messages in insignificant media before a transmission. Information-hiding schemes are used to hide secrets in cover media, producing stego-media. The approach enables users to discover attempts by intruders to replace original messages with fabricated content. The objective of data hiding is to increase the capacity for hidden secrets while reducing the likelihood that intruders identify them. In this dissertation, three new data hiding schemes are proposed. Two of them are blind and reversible. The first steganographic scheme presents a new data hiding scheme that is based on transforming the data to be covertly transmitted into a high-frequency signal, which is then carried by an audible public music signal. The principle is as follows: The secret message is translated into a digital form, which is then transformed into a high-frequency signal. This high-frequency signal, which is above the threshold of human audibility, is integrated into a public music signal, which can be actively downloaded by legal receivers. The receiver will demodulate the high-frequency signal and recover the data. This proposed scheme greatly reduces the risk of exposure of the secret message during transmission. Experimental simulation and comparison are performed in this paper to investigate the practicability and the superior performance of the proposed method compared to the competing data hiding schemes. The second steganographic scheme works by adopting error-correcting-coding strategy to transform digital physiological signals into a new bit-stream that uses a matrix in which is embedded the Hamming code to pass secret messages or private information. The shared keys are the matrix and the version of the Hamming code. An online open database, the MIT-BIH arrhythmia database, was used to test the proposed algorithms. The time-complexity, capacity and robustness are evaluated. Comparisons of several evaluations subject to related work are also proposed. This work proposes a reversible, low-payload steganographic scheme for preserving the privacy of physiological signals. An (n-m)-hamming code is used to insert n-m secret bits into n bits of a cover signal. The number of embedded bits per modification is higher than in comparable methods, and the computational power is efficient and the scheme is secure. Unlike other Hamming-code based schemes, the proposed scheme is both reversible and blind. The third scheme is using synthesized music to hide data. Recently, social media are widely developed and users post their self-defined media. This makes self-defined based steganography is applicable. The advantage of self-defined is the synchronization of hiding and synthesis. It results “high capacity, low distortion”. From our experiments, the more synthesized steps executed, the numbers of bits are embedded and the synthesized music sounds more real. The proposed scheme conquers the bottleneck of steganography, which is, high capacity and high distortion.