1. Bit-level based secret sharing for image encryption Rastislav Lukac, Konstantinos N. Plataniotis Presented by Du-Shiau Tsai Pattern Recognition 38 (2005) 767 – 772

2. 2 Contents 1. Introduction 2. Visual Cryptography 3. The proposed scheme 4. Experiment results 5. Conclusions

3. 3 Introduction Secret image sharing (Tsai)

4. 4 Introduction Classification of SIS (Tsai) SIS visual Cryptography (1994) variant visual secret sharing (2000) interpolation method (2002)

5. 5 Introduction Visual cryptography is a secret sharing procedure for image data Recover the secret by the human visual system Without additional computations and any knowledge of cryptography.

6. 6 Introduction Unfortunately, visual sharing schemes cannot restore to its original quality when the original input is a natural image. The proposed scheme operates directly on the bit planes of the digital image

7. 7 2-out-of-3 Visual Cryptography SASA SBSB SCSC

8. 8 2-out-of-2 Visual Cryptography B

9. 9 More reasons for the proposed scheme cannot provide perfect reconstruction intensity or spatial resolution is not appropriate for real-time applications.

10. 10 The proposed scheme

11. 11 Example: The (2,2) proposed scheme for 4-bit image 12=1011=1*2 3 + 0*2 2 + 1*2 1 + 1 5=0101=0*2 3 + 1*2 2 + 0*2 1 + 1

12. 12 Experiment results

13. 13 Conclusions Preserve all the features of traditional k-out-n sharing schemes Allow for perfect reconstruction of the input B- bit image Encrypts binary, gray-scale and color images Can be effectively implemented either in software or hardware