2. ELE 488 F06 ELE 488 Fall 2006 Image Processing and Transmission (12 – 7 – 06) Digital Watermarking What? Why? How? Attacks, Legal issues 12/7

3. ELE 488 F06 Digital Watermark What? –secondary information in perceptual media data –examples: picture in picture, words in words, data in data, sound in sound Why? How?

4. ELE 488 F06 Vatican Digital Library –Founded 1451 by Pope Nicholas V –150,000 manuscripts (trace back to 300~400 AD) –1.5 million books –only 2,000 scholars visit each year –security

5. ELE 488 F06 from IBM web page IBM - Vatican Library

6. ELE 488 F06 Picture in Picture

7. ELE 488 F06 Picture in Picture

8. ELE 488 F06 Picture in Picture http://www.cl.cam.ac.uk/~fapp2/steganography/image_do wngrading/

9. ELE 488 F06 Is seeing believing?

10. ELE 488 F06 All for a royal smile LONDON, June 21 - One of the official photographs of the wedding of Prince Edward and Sophie Rhys-Jones last Saturday was doctored because Prince Williams ….. did not look happy enough …. From the New York Times, June 22, 1999

11. ELE 488 F06 E-files: binary “images”

12. ELE 488 F06 Authorized and unauthorized modification

13. ELE 488 F06 Document Authentication alter

14. ELE 488 F06 Words in Words

15. ELE 488 F06 Digital Watermark What? –Secondary information in perceptual media data Why? –To convey other information –To Detect Alteration Easy to modify  authentication Easy to copy without degradation  ownership Seeing is believing? How?

16. ELE 488 F06 Picture in Picture http://www.cl.cam.ac.uk/~fapp2/steganography/image_do wngrading/

17. ELE 488 F06 Additional Functionality – error concealment

18. ELE 488 F06 How can watermark help to detect alteration?

19. ELE 488 F06

20. Document Authentication –Embed prescribed pattern or content features beforehand –Verify hidden data’s integrity to decide on authenticity (f) alter (a) (b) (g) after alteration (e) (c) (d)

21. ELE 488 F06 Document Authentication –Embed prescribed pattern or content features beforehand –Verify hidden data’s integrity to decide on authenticity (f) alter (a) (b) (g) after alteration (e) (c) (d)

22. ELE 488 F06 Digital Watermark What? –Secondary information in perceptual media data Why? –To Detect Alteration Easy to modify  authentication Easy to copy without degradation  ownership Seeing is believing? –Convey other information How? –Insertion and detection Replacing LSB Fragile watermark Robust watermark Binary images (documents)

23. ELE 488 F06 Picture in Picture http://www.cl.cam.ac.uk/~fapp2/steganography/image_do wngrading/

24. ELE 488 F06 Replacing LSB UMCP ENEE631 Slides (created by M.Wu © based on Research Talks ’98-’04)

25. ELE 488 F06 Replacing LSBs Replace 6 LSBs with Pentagon’s 6 MSBs UMCP ENEE631 Slides (created by M.Wu © based on Research Talks ’98-’04)

26. ELE 488 F06 Fragile WM to Detect Modification Yeung & Mintzer ICIP’97

27. ELE 488 F06 Fragile WM - Pixel-domain Table-lookup - Pro: simple; be able to localize alteration extracted wmk from altered image

28. ELE 488 F06 # of changeable coeff: 0-30 / blk embed 1bit/blk by repetition Embed in Compressed Domain limit LUT runs of 1’s and 0’s DC and small coeffs not modified

29. ELE 488 F06

30. Difficulties: smooth region –smooth region  difficult to embed, uneven embedding –solutions: backup, shuffling –use ‘error difusion’ in pixel domain embedding

31. ELE 488 F06 Uneven embedding capacity

32. ELE 488 F06 –embedding rate  … >= 1 bit / block Wu-Liu Scheme: shuffling (cont’d)

33. ELE 488 F06 Embedding and Extraction –What to embed? @ @ meaningful pattern: facilitate quick visual check and locate alteration low-level content-based features to help detect alteration

34. ELE 488 F06 Fridrich & Goljan ICIP 99

35. ELE 488 F06 Ideas –Place wmk in perceptually significant spectrum –use random vector as wmk to avoid artifacts –scaling N=1000 largest AC coeff. {v i } by a random factor –w i – iid, zero mean, unit variance Embedding: v i ’ = v i (1+a w i ), a ~ 0.1 How to extract w ? 2D DCTsortv’=v (1+a w) IDCT & nomalize original image N largest coeff. other coeff. marked image N random numbers wmk seed Robust Watermark - Spread Spectrum Embedding (NEC scheme, Cox’s scheme)

36. ELE 488 F06 Detection: based on hypothesis testing –measure and threshold the similarity between Y & W DCT compute similarity threshold test image decision wmk DCTselect N largest original unmarked image select N largest preprocess - - orig X test X’ X’=X+W+N ? X’=X+N ?

37. ELE 488 F06 Random sequence of 1 and –1 1 1 1 -1 -1 1 -1 line up x) 1 1 1 -1 -1 1 -1 1 1 1 1 1 1 1 sum = 7 1 1 1 -1 -1 1 -1 shift 1 1 1 -1 -1 1 -1 1 1 -1 1 -1 -1 sum = 0 1 1 1 -1 -1 1 -1 0 shift 2 0 1 1 1 -1 -1 1 -1 1 -1 -1 -1 1 sum = -1 shift 3, sum = 0 shift 4, sum = -1 shift 5, sum = 0 shift 6, sum = -1 results symmetric if shifted to the left. Correlation: -1 0 -1 0 -1 0 7 0 -1 0 -1 0 -1

38. ELE 488 F06 100 binary random numbers correlation

39. ELE 488 F06 Two binary random sequences cross correlation

40. ELE 488 F06 1000 random numbers (-1, 1)

41. ELE 488 F06 x: 1 or -1, s = sine signal, sx = s+.05*x, correlate x & sx

42. ELE 488 F06 Cox’s Scheme (cont’d) Robustness: –(claimed) scaling, JPEG, dithering, cropping, “printing- xeroxing-scanning”, multiple watermarking Comment: –must store original unmarked image  “private wmk” –perform registration if necessary –adjustable parameters: N and 

43. ELE 488 F06 Examples... wmk & distortions Original JPEG 10% (~30:1 compression) lowpass –Robust watermark are designed to survive distortions: marked orig. wmk distorted distortion

44. ELE 488 F06 Compare NEC & Bell schemes Orig.?NEC ?Bell – PU ?

45. ELE 488 F06 Compare NEC & Bell schemes (cont’d) NECBell - PU

46. ELE 488 F06 Document (AT&T) from http://www.acm.org/~hlb/publications/dig_wtr/dig_watr.html

47. ELE 488 F06

49. OriginalAltered (flipx=2000)

50. ELE 488 F06 The Difference

51. ELE 488 F06 References F. Mintzer, G.W. Braudaway, M.M. Yeung, “Effective and Ineffective Digital Watermarks”, IEEE ICIP 97 Cox, J. Kilian, T. Leighton, T. Shamoon: “Secure Spread Spectrum Watermarking for Multimedia'', IEEE Trans Image Processing, Dec 1997 M Wu, B Liu, “Watermarking for image authentication”, ICIP 98. M. Wu, B. Liu, “Data Hiding in Binary Images for Authentication and Annotation", IEEE Trans Image Processing, August 2004. J. Fridrich, M. Goljan,”Image with Self-correcting Capabilities, ICIP 1997