Recover the tampered image based on VQ indexing Source: Signal Processing, Volume 90, Issue 1, Jan. 2010, pp Authors: Chun-Wei Yang and Jau-Ji Shen Reporter: Te-Yu Chen( 陳德祐 )

Outline Introduction The Proposed Scheme  VQ Index Embedding and Watermark Embedding  Wong et al.’s Watermarking Schemes for Authentication and Ownership Verification  Watermark Extraction and Image recovery Experimental Results Conclusions & Comments 2

Watermarking Data Image Authentication with Tamper Detection and Recovery Public channel Embedding Yes OK No Original image Watermarked image Received image Recovered image Tamper recovery 3

WatermarkingWorking DomainSpatialFrequencyRobustnessRobustSemi-FragileFragilePerceptionVisibleInvisible Necessary Data for Extraction Blind (Public) Semi-Blind (Semi- Public) Non-Blind (Private) 4

Requirements Ability of tamper detection Ability of tamper recovery Image quality Resistant to known attacks  Tamper watermarked image without being detected Counterfeit attack  Collage attack  VQ attack Blind attack Cropping  Trace out the mapping correlation of blocks The four-scanning attack(brute-force/dictionary attack) 5

Literature 1.A Hierarchical Digital Watermarking Method for Image Tamper Detection and RecoveryA Hierarchical Digital Watermarking Method for Image Tamper Detection and Recovery  Phen-Lan Lin, Chung-Kai Hsieh, and Po-Whei Huang, Pattern Recognition, Vol. 38, Issue 11, A Majority-voting Based Watermarking Scheme for Color Image Tamper Detection and RecoveryA Majority-voting Based Watermarking Scheme for Color Image Tamper Detection and Recovery  Ming-Shi Wang and Wei-Che Chen, Computer Standards & Interfaces, 29, pp , Dual Watermark for Tamper Detection and RecoveryDual Watermark for Tamper Detection and Recovery  Tien-You Lee and Shinfeng D. Lin, Pattern Recognition, 41(11), pp , Four-scanning attack on hierarchical digital watermarking method for image tamper detection and recoveryFour-scanning attack on hierarchical digital watermarking method for image tamper detection and recovery  Chin-Chen Chang,Yi-Hsuan Fan, and Wei-Liang Tai, Pattern Recognition, Vol. 41, Issue 2, Feb. 2008, pp Watermarking for tamper detection and recovery  Youngran Park, Hyunho Kang, Kazuhiko Yamahuchi, and Kingo Kobayashi, IEICE Electronics Express, 5(17), pp , Recover the tampered image based on VQ indexing  Chun-Wei Yang and Jau-Ji Shen, Signal Processing, 90(1), 2010, pp

Comparisons 7

Watermarking 1n32 1 n 32 8

The Proposed Scheme~ Embedding 9 Recovery Information Recovery Information Verification Information Verification Information

Recovery information ~VQ Encoding Index Table Original Image Codebook ‧ 168 ‧ 255 (150,135,…,128) … (20,65,…,110) (90,135,…,120) (120,155,…,80) (50,42,…,98) (49,117,…,25) (100,125,…,150) …

Verification information ~ Wong’s watermarking scheme(Embedding) 12

Image block H r = H(256, 256, 1016, 1, 130, 50, 120, 80) = … F r = H r ⊕ Br = 1101 ⊕ 0100 = 1001 P r = E k’ (F r ) = E k’ (1001) = 0011 Watermarked block Wong’s watermarking scheme~ Embedding 13 NCHU Original Image M o : the image width (256) N o : the image height (256) I o : the image ID (1015) r: the block index (1) the r-th image block after setting LSB1 to 0 (130, 50, 120, 80) Watermarked Image

The Proposed Scheme~ Tamper detection and recovery 14 Detection Recovery

Wong’s watermarking scheme~ Detection 15

16 10

Recovery information ~VQ Recovery Recovered Image Codebook ‧ 168 ‧ 255 (150,135,…,128) … (20,65,…,110) (90,135,…,120) (120,155,…,80) (50,42,…,98) (49,117,…,25) (100,125,…,150) … 17

Original Tampered (56% cropped) Lee and Lin’s scheme PSNR=26.75dB The proposed scheme PSNR=29.33dB Experimental Results Image size: 256×256 pixels CB size: 256 code words Code word:4×4 pixels IT can be embedded into O four times 18 CB size: 256×4×4×256 bits

Tampered Recovered Tampered Recovered PSNR=31.70dB31.72dB30.91dB31.69dB PSNR=31.28dB31.99dB30.33dB31.72dB 19

35.24 dB dB dB Tamped Image Tamper detected images The recovered images 20

49%61%65%70% 75%80%85%90% 29.83dB 29.16dB 28.62dB 27.66dB 26.30dB 24.41dB 22.59dB 20.12dB 21

Conclusions An image tamper detection and recovery scheme integrating Wong’s watermarking scheme and VQ is proposed. The number of times of embedding the recovery info. into the image is adjustable. The quality of the recovered image is high. Resistant against the known attacks. (Wong et al.’s scheme is adopted) 22

Comments Owing to the use of a public key cryptographic system, the block size should be large enough for the security concern(1024bits). However, the larger the block size is, the less precision of error detection will be. Owing to the use of a public key cryptographic system, the computational cost is high. Additional cost: code book(4×4 ×256×256 bits) 23