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隱 像 術

隱 像 術. 張真誠 國立中正大學資訊工程研究所. 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. Apply the Traditional Cryptosystem on Images.

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隱 像 術

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  1. 隱 像 術 張真誠 國立中正大學資訊工程研究所

  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.

  3. Apply the Traditional Cryptosystem on Images

  4. 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)

  5. Virtual Image Cryptosystem

  6. Vector Quantization Encoder

  7. Vector Quantization Decoder

  8. 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, … , Vnv} • Let O be the original image • Let {V1, V2, V3, …, Vnv} be the codebook

  9. 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}

  10. 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

  11. Decryption

  12. Empirical Tests Test1: Original Image Airplane 512 X 512

  13. Virtual Image Lena 256 X 256 Cipher Image Lena 256 X 256 PSNR=37.87dB

  14. Decrypted Image Airplane 512 X 512 PSNR=30.22dB

  15. Test2: Original Image Airplane 512 X 512

  16. Virtual Image Lena 360 X 360 Cipher Image Lena 360 X 360 PSNR=45.13dB

  17. Decrypted Image Airplane 512 X 512 PSNR=31.36dB

  18. Test3: Original Image Peppers 512 X 512

  19. Virtual Image Lena 256 X 256 Cipher Image Lena 256 X 256 PSNR=37.60dB

  20. Decrypted Image Peppers 512 X 512 PSNR=29.91dB

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