臺灣博碩士論文加值系統

隨著科技的進步，數位視訊資料的傳輸應用已經越來越普遍，例如視訊會議系統、線上付費電視等，這些都有可能在網路上為有心人士所竊取，為了防止竊取，所以多媒體資料的加密是一極端重要的議題。因此在本篇論文中，我們實作一合適而且不至於嚴重影響系統效能和壓縮率的視訊加解密系統。
因為，不論在時間域或頻率域上作位元擾亂的動作均會嚴重影響到系統的編碼效能或壓縮率。且在壓縮域的加密方法中[2]，第一種加密方法在移動向量個數較多的情形下，對壓縮率亦會有些許影響。因此，我們選定對霍夫曼碼表作修改，實驗結果顯示這種加解密方法對於原有壓縮系統之效能及壓縮率的影響都不大。
為了建構可以達到快速且不致嚴重影響壓縮率的加密系統，首先，我們提議使用外張樹演算法，對固定長度碼表和可變長度碼表作擾亂的動作，來達到加密的效果；接著，我們利用混沌演算法來快速地產生金鑰。此外，本系統亦可做到多重保密效果。

With the advancement of science and technology, the transmission of digital video data becomes more and more popular. Such as video conference system and online pay-TV which may be grabbed by a hacker. Hence, in order to prevent data piracy and plagiarism, the encryption of multimedia data becomes an extremely important issue. In this paper, we propose an efficient encryption framework which wouldn’t influence seriously the coding speed and compression efficiency of the original codec system.
Since, no matter while employing bit-scrambling techniques on the data in the time domain or frequency domain, which would influence the performance of the codec system seriously. Besides, the first method of the compression domain based encryption algorithms proposed in [2] is also less efficient under the situation that there exists a large amount of motion vector codewords in the coded bitstream. Hence, we proposed a lightweight encryption framework through the modification of Huffman tables and it was implemented and verified to be efficient while embedded in H.263+ codec.
In order to construct an encryption system which could still own the fast coding speed and better compression efficiency. First, we propose to scramble the fixed-length code (FLC) tables and variable-length code (VLC) tables by using the splay tree algorithm. Next, we use the chaotic algorithm to produce the secret key more promptly and confidentially. Furthermore, different configurations of security can be achieved by easily adapting our system.

內容目次---------------------------------------------------------------------1
圖目目次---------------------------------------------------------------------2
表目目次---------------------------------------------------------------------4
第一章 簡介------------------------------------------------------------5
1.1 研究動機-----------------------------------------------------------5
1.2 論文架構-----------------------------------------------------------8
第二章 相關研究-----------------------------------------------------9
2.1 時間域上的選擇性擾亂----------------------------------------10
2.2 頻率域上的選擇性擾亂----------------------------------------12
2.3 霍夫曼碼表的設計----------------------------------------------22
2.4 壓縮域上的字碼擾亂-------------------------------------------31
第三章 提議的視訊加解密架構------------------------------------35
3.1 利用混沌演算法產生金鑰-------------------------------------35
3.2 利用擾亂編碼表的方式來達到加密-------------------------40
3.3 安全性分析-------------------------------------------------------51
3.4 多重保密效果----------------------------------------------------56
第四章 實驗結果------------------------------------------------------58
第五章 結論及未來展望------------------------------------------------69
5.1 結論-------------------------------------------------------------------69
5.2 未來展望-------------------------------------------------------------71
參考文獻---------------------------------------------------------------------72

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