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Multiple-Image Encryption by Rotating Random Grids

Multiple-Image Encryption by Rotating Random Grids. Authors: Tzung-Her Chen, Kai-Hsiang Tsao, and Kuo-Chen Wei Source: Proceedings of The 8th International Conference on Intelligent System Design and Applications (ISDA 2008) 學生：張若怡 P78011044 許伯誠 P76011242 Date: 2013/01/18. Outline.

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Multiple-Image Encryption by Rotating Random Grids

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  1. Multiple-Image Encryption by Rotating Random Grids Authors: Tzung-Her Chen, Kai-Hsiang Tsao, and Kuo-Chen Wei Source: Proceedings of The 8th International Conference on Intelligent System Design and Applications (ISDA 2008) 學生：張若怡 P78011044 許伯誠 P76011242 Date: 2013/01/18

  2. Outline • Introduction • Motivation • Related Work • Research Methods • Encryption phase • Decryption phase • Research Results • Conclusion

  3. Introduction – Visual Cryptography • Traditional Cryptography • - Encryption and Decryption by computer • Visual Cryptography (VC), also called Visual Secret Sharing (VSS) • - Encrypted by computer, Decrypted by human vision

  4. Introduction • Traditional VC and Random Grid • VSS • Traditional VC-based VSS (Codebook) • RG-based VSS (Random Grid) • Traditional VC-based VSS has at least two drawbacks asfollows : • Codebook design • Pixel expansion

  5. Introduction • Pixel expansion Traditional VC-based VSS: Share1 Secret image Share2 Share1 + Share2

  6. Introduction • Traditional VC and Random Grid • VSS • Traditional VC-based VSS (Codebook) • RG-based VSS (Random Grid) • Traditional VC-based VSS has at least two drawbacks asfollows : • Codebook design • Pixel expansion

  7. Motivation SA G1 SA’ G2 SA SA’ SB SB’ G1 G2

  8. Related Work In 1987, Kafri and Keren propose three different algorithms to encrypt a binary secret image. Random Grid Algorithm1: for(i=0 ; i<w ; i++) for(j=0 ; j<h ; j++) if(B[i][j] == 0) G2[i][j] = G1[i][j]; else G2[i][j] = G1[i][j]; Output(G1 , G2); SA G1 G2 • O. Kafri, and E. Keren, “Encryption of pictures and shapes by random grids,” Optics Letters, vol. 12, no. 6, 1987, pp. 377-379.

  9. Research Methods

  10. Research Methods Encryption phase: • Step 1: SA(i, j) ← f RSP(SA). • Randomly select a pixel SA(i, j) from the first secret image SA, where the i-th row and the j-th column of the matrix SA are in the range of [0,m-1]. • Step 2: G1(i, j)||G2(i, j) ← f RG(SA(i, j))

  11. Research Methods

  12. Research Methods

  13. Research Methods • Step 8: G1((m-1)-j, i) ← random(0,1)

  14. Research Methods • Decryption phase

  15. Research Results • Simulation 1: binary secrets, 90-degree rotation • Two secret images SA and SB with the size of 512×512

  16. Research Results • Simulation 2: Halftone secrets, 90-degree rotation • Two gray-level secret images SA and SB with the size of 512×512

  17. Research Results • Simulation 3: binary secrets, 180-degree rotation • Simulation 4: binary secrets, 270-degree rotation

  18. Conclusion • Property 1: No extra codebook redesigned • Property 2: No extra pixel expansion introduced • Property 3: Multiple secrets encoded • Property 4: Bandwidth and storage saving • Property 5: Wide image format

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