1. 1 Commutative Encryption and Watermarking in Video Compression 交換式加密及浮水印法應用在視頻壓縮 IEEE Transactions on Circuits and Systems for Video Technology, VOL. 17, NO. 6, June 2007 Author ： Shiguo Lian, Zhongxuan Liu, Zhen Ren,Haila Wang Adviser ：鄭錦楸, 郭文中 教授 Reporter ：林彥宏

2. 2 Outline Introduction Research Method Watermarking and Encryption Scheme Proposed Encryption Process Proposed Watermarking Process Watermark Extraction Performance Analysis Security Robustness and Imperceptibility Commutation Conclusions

3. 3 Introduction(1/6) H.264/AVC(Advanced Video Coding) Intra-Prediction mode (IPM) I-frame (Intra) P-frame (Unidirectional Predication) B-frame (Bidirectional Predication)

4. 4 Introduction(2/6) intra_4x4

5. 5 Introduction(3/6) intra_16x16

6. 6 Introduction(4/6) Inter-Prediction mode block size selection={16 ×16, 8×16, 16 ×8, 8 ×8, 4 ×8, 8 ×4, 4 ×4 }

7. 7 Introduction(5/6)

8. 8 Introduction(6/6) Motion Vector Difference (MVD) Temporal Redundancy Spatial Redundancy Residue Data

9. 9 Research Method Proposed watermarking and encryption scheme based on H.264/AVC

10. 10 Watermarking and Encryption Scheme be composed of two independent parameters and encrypted copy of watermarked copy of watermark key encryption key encryption algorithm watermark algorithm

11. 11 Proposed Encryption Process MVD Encryption ： Signs of MVD are encrypted Exp-Golomb code (2M+1) 0 → 1 → 1 1 → 10 → 010 2 → 11 → 011 3 → 100 → 00100 4 → 101 → 00101 5 → 110 → 00110 …..

12. 12 Proposed Encryption Process IPM Encryption ： EX ： 0001011 Residue Encryption ： each non-zero residue macroblock DCT coefficients are encrypted partially first 8 coefficients’ signs in each 4×4 DCT block are encrypted

13. 13 Proposed Watermarking Process watermark embedding is composed of three steps ： Block Selection ： 1) residue block is nonzero 2) for I/P-frame, residue DCT block is composed of only ac 3) for B-frame, residue DCT block is composed of either dc or ac

14. 14 Proposed Watermarking Process Coefficient Selection ： coefficient in middle frequency are preferred Watermark Embedding ： if is watermark is original coefficient is quantization step

15. 15 Proposed Watermarking Process if otherwise ex ：

16. 16 Proposed Watermarking Process

17. 17 Watermark Extraction Watermark Extraction ：

18. 18 Performance Analysis Security ： 128-bit AES (Advanced Encryption Standard )

19. 19 Robustness and Imperceptibility

20. 20 Commutation

21. 21 Commutation

22. 22 Conclusions The modified watermarking algorithm makes the watermarking operation and encryption operation commutative. The scheme keeps secure against present attacks, is efficient in implementation, keeps imperceptible, and is robust against recompression in some extent.