1 影像偽裝術的最新發展 張真誠 逢甲大學 講座教授 中正大學 榮譽教授 清華大學 合聘教授

2 1. Watermarking 2. Image authentication 3. Secret sharing 4. Visual cryptography 5. Steganography

3 Watermarking Visible watermarking Easy to embed Clear to see watermark

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

5 Image authentication Requirements: Detect the tampered area Try to restore the tampered area Image Tampered imageDetected imageRestored image

6 Secret sharing Classification: Meaningless shadows Meaningful shadows

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

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

9 Visual cryptography Shadow 1Shadow 2 Secret Stacking

10 Visual cryptography (Cont.) Shadow 1Shadow 2 Secret Stacking

11 Visual cryptography (Cont.) Share 1 Share 2 Secret 1 “ VISUAL ” Secret 2 “ SECRET ” Stacking Rotating 40 o

12 Steganography The targets Frequency domain (e.g. DCT, DWT, DFT) Spatial domain (e.g. pixel values) Compression domain (e.g. VQ) Text Restoration Irreversible Reversible

13 Steganography (Cont.) Cover image Hiding system Secret message Stego image Image

14 Steganography (Cont.) Text 壞的毛病 壞毛病 山東的蘋果 山東蘋果 我的媽媽 我媽媽 主要的問題 主要問題 另外的一件事 另外一件事 其他的問題 其他問題 北京的大學 北京大學 Video Sound

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

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

17 Sudoku A logic-based number placement puzzle

18 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.

19 Data Hiding Using Sudoku - 1 Reference Matrix M

20 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.

21 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: …

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

23 Experimental Results

24 Experimental Results (Cont.) The results of visual quality and Embedding capacity comparisons Images Proposed PSNRC Baboon Barbara Boats Goldhill Jet(F16) Lena Pepper Sailboat Tiffany Average