運用可變長度編碼及隨機位元插入之視訊加解密技術研究

Abstract

在這篇論文裡，我們依據黃日良學長和王聖智老師在2001年提出的加解密架構，做改良以提高其安全度。他們的加解密架構的主要概念在於加密可變長度碼表。為了提高安全度，我們利用隨機位元插入法和隨機位元轉換法來打亂密文的統計特性；另外，我們也打亂RLC(run-length coding)的對應關係，以增加被攻擊的困難度。我們的加解密架構係以MPEG-4實現，並能達到即時傳輸。在論文中，我們也討論到我們的加解密架構的安全度及所可能遭受到的攻擊。值得一提的是，我們的加解密架構抵抗雜訊的能力並不因為加解密的訴求而降低。

In this paper, we propose a new video encryption algorithm, which is based on the encryption scheme proposed by Huang and Wang in 2001. In Huang’s approach, the encryption operation is fulfilled via the modification of VLC tables. Based on this encryption scheme, we made a few modifications to greatly enhance its security level. The modifications include the use of randomized bit-insertion and bit-flipping to complicate the statistics of ciphertexts and the use of RLC (run-length coding) disarrangement to increase the difficulty in cryptanalysis. This algorithm can be easily employed over an MPEG-4 codec to achieve real-time encryption. The security levels of this proposed algorithm against various types of attacks are also discussed. Moreover, the encrypted data have about the same level of noise sensitivity as the original MPEG-4 bit-stream.