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    Please use this identifier to cite or link to this item: http://asiair.asia.edu.tw/ir/handle/310904400/9621

    Title: 以適應性資訊隱藏技術為基礎的光學影像加解密系統之研究
    Authors: 莊政宏
    Contributors: 資訊學院
    Keywords: 資料嵌入
    data embedding
    data hiding
    data encryption
    image cryptosystem
    optical security
    double-random-phase encoding
    Date: 2007
    Issue Date: 2010-05-13 13:53:41 (UTC+8)
    Abstract: 本計畫提出一種運用適應性資訊隱藏技術的光學影像加解密系統,此系統具有低失真以及以影像內容為依據的資料隱藏方法,並具有較高的安全性,可作為影像及多媒體訊號傳輸上之應用。此計畫中之光學影像加解密系統,乃是利用一種雙隨機相位編碼演算法,對影像進行加密及解密的動作,並且以非對稱的方式,利用資料隱藏技術將秘密金鑰的傳遞建構於影像中。一般的方法,是利用頻域中之高頻區域,在固定的位置上,以其係數值的部分進行量化,再利用LSB (least significant bit)進行資料隱藏。然而,此方式非但不安全,在隱藏的資料量大的時候,以及量化位階較少的時候,其重建影像的品質不盡理想。本研究所提出新的演算法,將根據不同的影像內容,以適應性的資訊隱藏技術將秘密金鑰藏匿於影像中,並且將研發利用壓縮技術對隱藏的資料或是藏匿的影像訊號進行壓縮,以期減少需藏匿的資料量及釋放一些隱藏的空間。本研究中提出之架構,將可改進傳統之光學影像加解密系統,使資料隱藏更具安全性,同時可大幅提升重建影像的品質。
    This study will propose a public-key-based optical image cryptosystem with adaptive steganography, in which a very low distortion and image content-dependent data embedding method will be presented for practical secure communications. The optical image cryptosystem employs a hybrid architecture where a double random-phase encoding algorithm is used to cipher and decipher images and an asymmetric method is used to encrypt and decrypt session keys. The key delivery is achieved by hiding secret messages, i.e. encrypted session keys, into least significant bits (LSBs) of some quantized coefficients of the ciphered images and extracting the secret data at the receiver side from the ciphered images. Then the images are reconstructed using the decrypted session keys. In the conventional method, the secret data is hidden in a fixed embedding area of the high-frequency band. However, the type of a fixed embedding area decreases the security. Furthermore, the image visual quality without channel distortions is not good when the quantization level is low and the amount of hidden data is large. An important part of this study is to investigate strategies to obtain hiding positions with a specific hiding sequence to embed a significant amount of data without causing noticeable artifacts. Moreover, compression techniques will be applied to reduce the amount of embedded data or release more free hiding space, i.e. embedded data or cover signal compression. To sum up, the newly proposed cryptosystem will have a better performance in hiding data and allow reconstructed images to reach a higher visual quality in the receiver side.
    Appears in Collections:[資訊工程學系] 科技部研究計畫

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