隱 像 術
Post on 31-Dec-2015
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2
Introduction
Images have been widely used in our daily life.
The image security has become an important issue in current computer world.
Image cryptology is a very useful tool to defend the information security.
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Problems
•The cipherimage is meaningless.
Image Camouflage( 影像偽裝 )
•Image size is huge
Image Compression( 影像壓縮 )
•The decrypted image containing a small distortion is usually acceptable.
Vector Quantization ( 向量量畫編碼法 )
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The Principle of the Virtual Image Cryptosystem
•Separate O into a set of vectors {O1, O2, O3,…, Ono}.
•Separate V into another set of vectors {V1, V2, V3, … , Vn
v}
•Let O be the original image
•Let {V1, V2, V3, …, Vnv} be the codebook
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Encryption
•Randomly generate the transformed-origin G and the project-direction D.
•Project {V1, V2, V3, …, Vnv} to D based on G
•Sort the projected results, and obtain {{V’1, V’2, V’3, …, V’nv}
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•Encrypt w, h, no, G, and D into wc, hc, noc, Gc, and Dc by DES-like, respectively.
•Encrypt I into Ic, where Ic=IXORX and X is the bit-string containing G, D, G, D,… only.
•Hide wc, hc, noc, Gc, Dc, and Ic into the pixels of V.
Cipher Image Vc
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