植基於向量量化編碼法與碼本查詢之資訊隱藏技術

隨著多媒體電腦網路技術的日新月異，透過網際網路上傳遞資料以非常簡單與便利，然而，這些公開通道在安全上是不足的，因為透過公開網路傳遞數位資料容易遭受修改、攔截以及偽造。儘管傳統密碼學技術能提供非常好的安全，不過遭加密後的資料通常會洩漏含有重要資訊情況，且遭加密後的資料可能會引起非法者或（駭客）的注意，所以提供一個安全的傳遞方式，資料隱藏將是一重要議題。資料隱藏或稱偽裝學是一種偽裝技術以提供安全傳遞的管道。資料隱藏與傳統密碼學技術不同地方，是將機密資訊潛藏入至偽裝掩護媒體之中，例如:影像、聲音、文件等。所以把資料潛藏至媒體之中，能夠減少引起非法者或（駭客）的注意和興趣。在這篇碩士論文，我們提出三個資料隱藏技術，第一個技術是植基於向量量化編碼法與主成分分析法，主要是利用主成分分析法來重新排列碼本內編碼字次序，接著將編碼本分割為兩個群組，且編碼字以均勻方式分佈群組中，以供將來在編碼選擇上可以減少重建影像品質不佳情形發生。第二個技術是利用碼本查詢方式，將灰階顏色分割為數個群組或分群集，每個群組分別都給予一個代號，代號是以隨機亂數產生器與種子產生，而在潛藏機密資訊位元同時將對應至群組代號，以加強資訊的安全性，此外將來可透過修改種子與亂數產生器以減少被探測的可能。第三個隱藏技術是基於區塊截短編碼與像素分群概念，利用兩個重建階和一張位元圖來潛藏秘密資料，重建階隱藏是以提出的第二個隱藏技術來進行兩重建階資訊隱藏，此外在位元圖隱藏採用漢明碼原理方式至BTC位元圖中潛藏機密資訊，以增加隱藏容量。

關鍵字

資料隱藏；向量量化編碼法；主成分分析法；分群；隨機亂數產生器；區塊截短編碼法

並列摘要

The increasing popularity of multimedia network technology, data transmission on the Internet becomes very easy and convenient. However, the pubic channel does not secure enough because digital data transmission on the public network is very easy to be modified, intercepted, and copied. Even though traditional cryptography schemes can provides very good security, however as an encrypted data normally reveals the importance of its content. The encrypted data might also attract the interest by hackers. To provide a secure transmission, data hiding becomes an important issue. Data hiding or called Steganography is a kind of camouflage approach which can provide a secure transmission. Data hiding differs from traditional cryptography schemes, in that it embeds secret information into normal host media such as images, music, and texts. It can decrease the suspect of the interest by the hackers because the embedded media does not look like it has valuable. In this thesis, we have proposed three data-hiding schemes. The first proposed scheme is based on the VQ encoding and the principal component analysis. The principal component analysis is used to reorder VQ codewords, and then to spilt them into two cluster groups. To decrease the reconstructed image quality, the codewords uniform selection is also provided. The second scheme uses the concept of the table lookup which partitions gray-level colors into several groups or called clusters. Each cluster is given a unique value by a pseudo random number generator with a known seed. Secret bits are then embedded into the selected groups. To increase the data security, a seed of the pseudo random number generator must be changed at each time for decreasing the possible detection. The third data hiding scheme is based on block truncation coding (BTC) scheme and the concept of pixels clustering. The proposed scheme utilities two reconstructed values and one bitmap of each BTC block to hide secret data. Two reconstructed values for each block uses the second proposed data hiding scheme to hide secret data On the other hand, for the binary bitmap, the Hamming code is applied to each binary bitmap of BTC blocks for increasing the hiding capacity.

並列關鍵字

Data Hiding ； Vector Quantization ； Principal Component Analysis ； Clusters ； Pseudo Random Number Generator ； Block Truncation Coding

參考文獻

[4] Rivest, R. L., Shamir, A. and Adleman, L., “A Method for Obtaining Digital Signatures and Public-Key Cryptosystems,” Communication of ACM, pp.120-126. 1978.

[7] Wang, R. Z., Lin, C. F. and Lin, J. C., “Image Hiding by Optimal LSB Substitution and Genetic Algorithm,” Pattern Recognition, Vol. 34, No. 3, pp. 671-683, March 2001.

[8] Thien, C. C., and Lin, J. C., “A Simple and High-Hiding Capacity Method for Hiding Digit-by-Digit Data in Images Based on Module Function,” Pattern Recognition, Vol. 36, pp. 2875-2881, 2003.

[9] Chang, C. C., Hsiao, J. Y. and Chan, C. S., “Finding Optimal LSB Substitution in Image Hiding by Dynamic Programming Strategy,” Pattern Recognition, Vol. 36, No. 7, pp. 1583-1595, 2003.

[10] Chan, C. K. and Cheng, L. M., “Hiding Data in Images by Simple LSB Substitution,” Pattern Recognition, Vol. 37, No. 3, pp. 469-474, 2004.

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植基於向量量化編碼法與碼本查詢之資訊隱藏技術

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