- 學位論文
新的數位影像加解密演算法及隱藏式視覺密碼演算法
NEW DIGITAL IMAGE ENCRYPTION/DECRYPTION ALGORITHMS AND HIDDEN VISUAL CRYPTOGRAPHY ALGORITHM
摘要
近幾年來，隨著網路世界蓬勃的發展及通訊系統與多媒體技術的飛速進步，多媒體通訊已經逐漸成爲人們之間資訊交流的重要管道；因此，資訊的安全與保密顯得越來越重要。尤其是針對影像資訊，由於網路頻寬的普及，影像資料在傳輸過程中容易被非法的使用者竊取、破壞或者更改，所以，對於影像資訊傳輸的保密性是一門越來越被重視的課題。 本論文的目的在於討論利用混沌系統的良好特性來對影像進行加密，進而提高其安全性；除此之外，我們也將討論視覺密碼學相關課題及應用。近年來，許多人開始漸漸應用混沌系統特性於密碼學，由於混沌系統對於初始值的敏感，因此，可以提高已加密資料的安全性，避免被非法使用者竊盜使用，我們會將其利用在Mojette Transform上面，除了可以達到錯誤更正碼的功能更可以增加影像資料上的安全性；另外，在視覺密碼學上，我們可以透過認證碼來判斷影像是否有遭受過變動。
並列摘要
In recent years, owing to the great development of communication system and multimedia technology, the multimedia communication has become an important role in communicating with people. The digital images can be altered and destroyed by the illegal user easily in the data transmission since the communications of digital products over open network occur more and more frequently. Hence, the security of digital images has become a critical issue. The purpose of this paper intends to take advantage of the features of the chaotic sequences to encrypt the digital images coded by Mojette Transform and to improve the security level. In addition, we will discuss the visual cryptography and its application. The Chaos has been applied to the cryptography in recent years. Chaotic sequences have several good properties including the ease of their generation, their sensitive dependence on their initial condition and noise like. It is very useful to strengthen the security of encrypted data to avoid the attack by the pirate. In this paper, we will achieve the error correcting ability of the received images and enhance the security by applying chaos to the Mojette Transform. On the other hand, we may apply the authentication code to judge the digital image whether has been suffered the change in the visual cryptography.