1 影像偽裝術的最新發展 Chair Professor Chin-Chen Chang Feng Chia University National Chung Cheng University National Tsing Hua University

2 Multimedia (Watermarking) Classifications: Visible watermarking Invisible watermarking Robust watermarking Semi-fragile watermarking Fragile watermarking

3 Multimedia (Watermarking) (Cont.) Visible watermarking Easy to embed Clear to see watermark

4 Multimedia (Watermarking) (Cont.) Invisible watermarking Requirements: Good visual quality of watermarked image Robustness Watermarking Watermarked imageOriginal image Watermark

5 Multimedia (Image authentication) Requirements: Detect the tampered area Try to restore the tampered area Solutions: Hamming codes Image Tampered imageDetected imageRestored image

6 Multimedia (Secret sharing) Classification: Meaningless shadows Meaningful shadows Meaningless shadows Requirements: Unexpected user can not see the secret image Good visual quality of reconstructed secret image

7 Multimedia (Secret sharing) (Cont.) Shadow size: 256  256 Image size: 512  512 Sharing Reconstructing PSNR=24 dB (2,4)-threshold secret sharing scheme

8 Multimedia (Secret sharing) (Cont.) Meaningful shadows Requirements: Good visual quality of stego image Secret image extraction and reconstruction Solutions: Applying steganography techniques Applying image authentication mechanisms

9 Multimedia (Secret sharing) (Cont.) Secret image Stego-image Hiding Reconstructed secret image Reconstructing (n,2)-threshold secret sharing scheme Stego-image

10 Multimedia (Visual cryptography) Requirements: Secret message delivery Unexpected user can not see the message from an individual share Solutions: Using shadow patterns Using meaningful shadow images Using Circle Shares

11 Multimedia (Visual cryptography) (Cont.) Shadow 1Shadow 2 Secret Staking

12 Multimedia (Visual cryptography) (Cont.) Shadow 1Shadow 2 Secret Staking

13 Multimedia (Visual cryptography) (Cont.) Share 1 Share 2 Secret 1 “ VISUAL ” Secret 2 “ SECRET ” Staking Rotating 40 o

14 Multimedia (Steganography) Classification: The target of modification Frequency domain (e.g. DCT, DWT, DFT) Spatial domain (e.g. pixel values) Compression domain (e.g. VQ, LAC, SOC) Stego image restoration Irreversible data hiding Reversible data hiding

15 Multimedia (Steganography) (Cont.) Irreversible data hiding Requirements: High capacity Good visual quality of stego images Solutions: Using Sudoku Using wet paper codes concept Using Hamming codes

16 Multimedia (Steganography) (Cont.) Reversible Requirements: Fully reconstructing cover image Good visual quality of stego image High capacity Solutions: Data hiding in VQ indices Data hiding in LAC codes Data hiding in SOC codes …

17 Data Hiding Cover image Hiding system Secret message Stego image

18 Cover Carriers Image Video Sound Text

19 VQ Encoding Codebook Index table (100,125,…,150) Original Image … (20,65,…,110) (90,135,…,120) (120,155,…,80) (50,42,…,98) (49,117,…,25)

20 Previous Work of Steganography on VQ To find the closest pairs

21 Unused CW 0, CW 8, CW 13, CW CW 1 CW 11,CW 2,CW 3 CW 4, CW 5 CW 6, CW 7 CW 15, CW 10 CW 12, CW 9 d(CW 0, CW 8 ) > TH d(CW 13, CW 14 ) > TH

22 Index Table Unused CW 0, CW 8, CW 13, CW 14 Encode Index Table Original Image

23 A secret message: Index Table CW 1, CW 2, CW 4, CW 5 CW 6, CW 7 CW 11, CW 3 CW 15, CW 10 CW 12, CW Secret bits

24 A secret message: Index Table CW 1, CW 2, CW 4, CW 5 CW 6, CW 7 CW 11, CW 3 CW 15, CW 10 CW 12, CW Secret bits

25 A secret message: Index Table Secret bits

26 Zhang and Wang ’ s Method (Embedding) … : … … … … … … … … … … … … :::::::::::: Magic Matrix Cover image Secret data: … Stego image p1p1 p2p2

27 Zhang and Wang ’ s Method (Extracting) … : … … … … … … … … … … … … :::::::::::: Magic Matrix Stego image Extracted secret data: p1p1 p2p2

28 Sudoku A logic-based number placement puzzle

29 Sudoku (Cont.) Property Possible solutions: 6,670,903,752,021,072,936,960 (i.e. ≈ 6.671×10 21 ) A Sudoku grid contains nine 3 × 3 matrices, each contains different digits from 1 to 9. Each row and each column of a Sudoku grid also contain different digits from 1 to 9.

30 Data Hiding Using Sudoku - 1 Reference Matrix M

31 Data Hiding Using Sudoku (Embedding) (Cont.) Cover Image Stego Image Secret data: … d(, ) = ((8-8) 2 +(4-7) 2 ) 1/2 =3 d(, ) = ((9-8) 2 +(7-7) 2 ) 1/2 =1 d(, ) = ((6-8) 2 +(8-7) 2 ) 1/2 =2.24 min.

32 Data Hiding Using Sudoku (Embedding) (Cont.) Cover Image Stego Image d(, ) = ((11-11) 2 +(15-12) 2 ) 1/2 =3 d(, ) = ((15-11) 2 +(12-12) 2 ) 1/2 =4 d(, ) = ((9-11) 2 +(14-12) 2 ) 1/2 =2.83 min Secret data: …

33 Data Hiding Using Sudoku (Extracting) (Cont.) Stego Image Extracted data: 27 9 =

34 Experimental Results

35 Experimental Results (Cont.) The results of visual quality and Embedding capacity comparisons

36 (7, 4) Hamming Coding Encoding Data: p 1 p 2 d 1 p 3 d 2 d 3 d d 1  d 2  d 4 = p 1 1  1  1 = 1 d 1  d 3  d 4 = p 2 1  0  1 = 0 d 2  d 3  d 4 = p 3 1  0  1 = 0 d1 d2 d3 d4d1 d2 d3 d4 Encoded data Encoding p 1 p 2 d 1 p 3 d 2 d 3 d 4

37 (7, 4) Hamming Coding (Cont.) Error Detection Received data: Error Position Corrected data: Correcting Parity check matrix H Error bit

38 Matrix Coding Method Cover Image Parity check matrix H ( ) T = (1 1 1) T Secret data: …  Stego Image Embedding

39 Matrix Coding Method (Cont.) ( ) T = (1 1 0) T Extracted secret data: … Stego Image Extracting ■ 7 pixels embed 3 bits

40 “ Hamming+1 ” Method Cover Image Parity check matrix H ( ) T = (1 1 1) T Secret data: …  ( ) mod 2= 1 = ? or( ) mod 2= Stego Image Embedding

41 “ Hamming+1 ” Method (Cont.) ( ) T = (1 1 0) T Extracted secret data: … = ( ) mod 2= Stego Image Extracting ■ 8 pixels embed 4 bits