1. 1 Security of fragile watermarking scheme for image authentication Authors: K. C. Liao, W. B. Lee, and C. W. Liao Source: The Imaging Science Journal, Vol. 54, No. 3, Sept. 2006, pp. 129-133. Speaker: Chia-Chun Wu ( 吳佳駿 ) Date: 2006/12/07

2. 2 Outlines Introduction Lu et al.’s Image Authentication Scheme Attack on Lu et al.’s Scheme Experimental Results Conclusion Comment

3. 3 Introduction Digital watermark for copyright protection, image authentication, etc. Two categories of digital watermarks:  Robust watermark:  for copyright protection.  Fragile watermark:  for image authentication.

4. 4 Lu et al.’s Image Authentication Scheme (1/5) 545 454 545 444 444 444 555 555 555 IIeIe IoIo 999 999 999 777 777 777 IocIoc IecIec encipher encipher: [0, 1, 2, 3,..., 254, 255] → K 1 → [98, 133, 11, 66,..., 201, 6] 000 000 000 111 111 111 b2b2 b1b1 XOR all Bit-planes XOR all Bit-planes Preprocessing: K1K1 K1K1 111 111 111 b3b3 XOR

5. 5 Lu et al.’s Image Authentication Scheme (1/5) 545 454 545 444 444 444 555 555 555 IIeIe IoIo 10 666 666 666 IocIoc IecIec encipher encipher: [0, 1, 2, 3,..., 254, 255] → K 1 → [98, 133, 11, 66,..., 201, 6] 000 000 000 000 000 000 b2b2 b1b1 XOR all Bit-planes XOR all Bit-planes Preprocessing: K1K1 K1K1 000 000 000 b3b3 XOR

6. 6 Lu et al.’s Image Authentication Scheme (2/5) 111 011 110 b4b4 545 454 545 I LSB substitute 555 455 554 I* (watermarked image) Watermark embedding: 111 111 111 b3b3 XOR 010 001 000 W K2K2 000 100 001 W'

7. 7 Lu et al.’s Image Authentication Scheme (2/5) 000 100 001 b4b4 545 454 545 I LSB substitute 444 544 445 I* (watermarked image) Watermark embedding: 000 000 000 b3b3 XOR 010 001 000 W K2K2 000 100 001 W'

8. 8 Lu et al.’s Image Authentication Scheme (3/5) Fig. 2 Block diagram for watermark embedding

9. 9 Lu et al.’s Image Authentication Scheme (4/5) 111 011 110 b4*b4* LSB 555 455 554 I* (watermarked image) Watermark extraction: 111 111 111 b3*b3* 000 100 001 XOR W' 010 001 000 W K2K2 same as in preprocessing

10. 10 Lu et al.’s Image Authentication Scheme (5/5) Fig. 3 Block diagram for watermark extracting * (watermarked image)

11. 11 Attack on Lu et al.’s Scheme (1/3) Statistical analyze 555 455 554 I* (watermarked image) 0,1→ 0 2,3→ 1 4,5→ 1 6,7→ 0. 254,255→ 0 look-up table 111 111 111 b3'b3' 000 000 000 b3"b3" complement Count(4) = 2 Count(5) = 7 > 1/2

12. 12 Attack on Lu et al.’s Scheme (2/3) look-up table 111 111 111 bY'bY' 000 000 000 b3"b3" complement 111 011 110 XOR b4b4 111 011 110 W" 545 454 545 Y 000 000 000 bY"bY" 555 455 554 I* (watermarked image) LSB (unwatermarked image)

13. 13 Attack on Lu et al.’s Scheme (3/3) 111 011 110 XOR b4'b4' 111 011 110 W" 545 454 545 Y 000 000 000 bY"bY" LSB substitute 555 455 554 Y* (watermarked image) (unwatermarked image)

14. 14 Experimental Results (1/5) Fig. 1 Tiling of logo image

15. 15 Experimental Results (2/5) NHS: normalized hamming similarity Fig. 4 (a) Host image ‘Lena’; (b) watermark image; (c) watermarked image; (d) extracted watermark, NHS=1.0

16. 16 Experimental Results (3/5) Fig. 5 (a) Modified watermarked image; (b) forged watermarked image; (c) extracted watermark, NHS=1.0 Type 1: Modification attack

17. 17 Experimental Results (4/5) Fig. 6 (a) Unwatermarked image; (b) forged watermarked image; (c) extracted watermark, NHS=1.0 Type 2: Counterfeit attack

18. 18 Experimental Results (5/5) Fig. 7 Error probability for different ratio of black pixel 10 binary image samples

19. 19 Conclusion Lu et al.'s fragile watermarking scheme is impractical. A forged watermarked image is likely to be produced without the consent of the original watermark owner.

20. 20 Comment (a) Lenna (b) Babon

21. 21 Comment (a) Lenna (stego image) (b) Baboon (stego image)

22. 22 Comment (a) Lenna (watermark) (b) Baboon (watermark) MSE = 0.00177764892578125 PSNR = 75.6323436612957 db