1 A Combined Approach to Integrity Protection and Verification of Palette Images Using Fragile Watermarks and Digital Signatures Source: IEICE TRANS. On FUNDAMENTALS, vol. E87-A, no. 6, pp. 1612- 1 619, Jun. 2004 Author: Chih-Hsuan Tzeng and Wen-Hsia ng Tsai Speaker: Na-I Wu ( 吳吳吳 ) Data: 2004/09/16
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1
A Combined Approach to Integrity Protection and Verification of Palette Images Using
Fragile Watermarks and Digital Signatures
Source: IEICE TRANS. On FUNDAMENTALS, vol.
E87-A, no. 6, pp. 1612- 1619, Jun. 2004
Author: Chih-Hsuan Tzeng and Wen-Hsiang Tsai
Speaker: Na-I Wu ( 吳男益 )
Data: 2004/09/16
2
Outline
• Introduction
• The proposed method
(1) Fragile watermarking embedding
(2) Generate “digital signatures”
• Experimental results
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Introduction An indexed image consists of data matrix, X, and a colormap matrix, map.
Size: 129 x 126
Ex: 256 色Indices:
form 1 to 256
File Size: Color map: 129 x 126 x 8 Indices: 256 x 3 x 8
6.19k bytes
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Introduction
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The proposed method Fragile watermarking embedding
To classify pixels into embeddable and non-embeddable
ones.
Embed
authentication
signals
Generate
Digital
signature
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Fragile watermarking embedding
• Raster Scanning Manner : to find “embeddable”, and “non-embeddable”
256 256 256 200 154 123 200 154
256 256 256 200 155 132 200 155
256 256 256 200 156 133 200 156
200 200 200 200 163 50 200 163
256 256 256 200 154 123 200 154
256 256 256 200 155 132 200 155
256 256 256 200 156 133 200 156
200 200 200 200 163 50 200 163
8x8
• Raster Scanning Manner : to find “embeddable”, and “non-embeddable”
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• Raster Scanning Manner : to find “embeddable”, and “non-embeddable”
P1(i-1, j-1) P2(i, j-1) P3(I+1, j-1)
P4(i-1, j) X(i,j)
Raster Scanning
Fragile watermarking embedding
α: the number of distinct colors of pixels in Prec(X)
β: The maximum color distance dmax(X, Prec(X))
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• How to compute α, β values
12 12 12
12 60 α = 1
12 12 16
10 10 α = 3
Fragile watermarking embedding
12(50, 60, 70) 轉成 L, a, b 顏色模式 (69, 10, 5)10(90, 10, 60) 轉成 L, a, b 顏色模式 (10, 7, 6)兩者的距離 =[(69-10)2+(10-7)2+(5-6)2]1/2