影像偽裝術 Dr. Chin-Chen Chang Department of Information Engineering and Computer Science, Feng Chia University, Taichung, Taiwan

Data Hiding Hiding system Stego image Cover image 1 0 1 0 1 0 0 1 0 1 1 1 1 0 0 Secret message

Cover Carriers Image Video Sound Text

Palette Image Conversion 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 (100,125,73) Index table Original Image Palette (16 colors)

To find the closest pairs Palette C0 C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 To find the closest pairs 5

d(C0, C8) > TH d(C13, C14) > TH Unused C0, C8, C13, C14 C1 C11

Encode Index Table Original Image Index Table Unused C0, C8, C13, C14

A secret message: 1 0 1 0 1 0 0 1 0 1 1 1 1 0 0 1 1 1 1 1 1 1 1 Index Table Secret bits C1, C2, C4, C5 C6, C7 C11, C3 C15, C10 C12, C9 1

A secret message: 1 0 1 0 1 0 0 1 0 1 1 1 1 0 0 1 1 1 1 1 1 1 1 Index Table Secret bits C1, C2, C4, C5 C6, C7 C11, C3 C15, C10 C12, C9 1

A secret message: 1 0 1 0 1 0 0 1 0 1 1 1 1 0 0 1 1 1 1 1 1 1 1 Index Table Secret bits

Adaptive Embedding Method C0 C1 C5 C3 C7 C6 C10 C14 C13 S1 C15 S0 S3 C4 C9 C2 C8 C11 C12 S2 S4

4 7 8 2 15 3 1 Secret message: (1 0 1 0 1 0 0 1 0)2 = (338)10 S2 S0 S4 15 3 1 S2 S0 S4 S3 S1 Index Table

C2 C4 C9 C0 C1 C6 C7 C14 C3 C5 C10 C13 C15 C0 C1 C6 C7 C14 C2 C4 C9 C8 C11 C12 C0 C1 C6 C7 C14 C2 C4 C9 S3 S2 S1 S2 S4 S2 S0 S0 S0 S2 X S0 X S1 X S3 X S0 X S2 X S4 X S0 X S2 ={(C2,C0,C3,C13,C0,C2,C8,C0,C2), (C2,C0,C3,C13,C0,C2,C8,C0,C4), (C2,C0,C3,C13,C0,C2,C8,C0,C9), …, (C9,C14,C10,C15,C14,C9,C12,C14,C9)}

0: (2,0,3,13,0,2,8,0,2) 1: (2,0,3,13,0,2,8,0,4) 2: (2,0,3,13,0,2,8,0,9) 338: (2,0,3,13,6,4,11,6,2) 32399: (9,14,10,15,14,9,12,14,9)

Tzeng et al.’s Data Hiding Index Color (133, 140, 128) 1 (123, 155, 130) 2 (130, 144, 138) 3 (126, 146, 134) 4 (139, 139, 143) 5 (131, 161, 124) 6 (137, 140, 144) 7 (137, 137, 140) C0 C1 C2 C3 C4 C5 C6 C7 Q: Ci > Cj A: ? The luminance function: l = 0.3*r + 0.59*g + 0.11*b The color-ordering relationship Palette

> ? < > ? Ex1: Q: A: Ex2: Q: A: c1 c2 (96,139,208) (119,159,227) c1 c2 l1 = 0.3*96 + 0.59*139 + 0.11*208 =133.7 l2 = 0.3*119 + 0.59*159 + 0.11*227 =154.5 < Q: A: > ? (245,130,44) (246,111,143) c1 c2 l1 = 0.3*246 + 0.59*111 + 0.11*143 =155 l2 = 0.3*245 + 0.59*130 + 0.11*44 =155 Ex2: Q: A:

Q: d(Ci , Cj)=? A: Ex1: C0 C1 C2 C3 C4 C5 C6 C7 Palette Index Color l (133, 140, 128) 136.6 1 (123, 155, 130) 142.7 2 (130, 144, 138) 139.1 3 (126, 146, 134) 138.7 4 (139, 139, 143) 139.4 5 (131, 161, 124) 147.9 6 (137, 140, 144) 139.5 7 (137, 137, 140) 137.3 C0 C1 C2 C3 C4 C5 C6 C7 Palette Q: d(Ci , Cj)=? A: Ex1:

Q: How to hide a secret bit A: Using color-mapping function Ex1: 7 4 6 5 2 3 1 in Image data 1 1 c’4 c’3 c’2 c’1 137.3 139.4 139.5 147.9

Ex2: 139.1 138.7 139.5 1

Embedding Process Image data X, palette P, and secret data A Check the data embeddability of each pixel Sort the colors of four precedent neighbors and perform the color- mapping function Is the mapped result equals the secret bit? No Yes Embed the secret bit by using the closest color of image data Embed the secret bit without modifying image data

Embedding Process If the secret data is 0 Palette Image data 7 4 6 5 2 Index Color l (133, 140, 128) 136.6 1 (123, 155, 130) 142.7 2 (130, 144, 138) 139.1 3 (126, 146, 134) 138.7 4 (139, 139, 143) 139.4 5 (131, 161, 124) 147.9 6 (137, 140, 144) 139.5 7 (137, 137, 140) 137.3 7 4 6 5 2 3 1 Image data Palette

Embedding Process If the secret data is 1 Palette Image data Index Color l (133, 140, 128) 136.6 1 (123, 155, 130) 142.7 2 (130, 144, 138) 139.1 3 (126, 146, 134) 138.7 4 (139, 139, 143) 139.4 5 (131, 161, 124) 147.9 6 (137, 140, 144) 139.5 7 (137, 137, 140) 137.3 7 4 6 5 2 3 1 Image data Palette 7 4 6 5 2 3 1 Embedded result

The Proposed Scheme The clustering c4 c6 c7 c5 c0 c2 c3 c1 S1 S2 S4 S3 Cluster S Index Color Center z S0 4 (139, 139, 143) (138, 139, 142) 6 (137, 140, 144) 7 (137, 137, 140) S1 5 (131, 161, 124) S2 (133, 140, 128) S3 2 (130, 144, 138) (128, 145, 136) 3 (126, 146, 134) S4 1 (123, 155, 130)

c4 c6 c7 c5 c0 c2 c3 c1 S1 S2 S4 S3 S0 Cluster S Index Color Center z Luminance l S0 4 (139, 139, 143) (138, 139, 142) 139 6 (137, 140, 144) 7 (137, 137, 140) S1 5 (131, 161, 124) 147.9 S2 (133, 140, 128) 136.6 S3 2 (130, 144, 138) (148, 145, 136) 144.9 3 (126, 146, 134) S4 1 (123, 155, 130) 142.7

7 4 6 5 2 3 1 c4 c6 c7 c5 c0 c2 c3 c1 S1 S2 S4 S3 S0 S c z l S0 4 (138, 139, 142) 139 6 7 S1 5 (131, 161, 124) 147.9 S2 (133, 140, 128) 136.6 S3 2 (148, 145, 136) 144.9 3 S4 1 (123, 155, 130) 142.7

Combination technique Secret data: (1011)2=(11)10 c6 S1 S2 c3 S4 Q=3x3x3=27 c7 S3 S0 7 4 6 5 2 3 1 c4 c4 c4 c4 c4 c4 c4 c4 c4 c6 c6 c6 c6 c6 c6 c6 c6 c6 c7 c7 c7 c7 c7 c7 c7 c7 c7 0001 0010 0000 6 4 7 5 2 3 1 c4 c4 c4 11th combination c6 c6 c6 c7 c7 c7

c4 c5 c0 c2 c1 c6 S1 S2 c3 S4 c7 S3 Secret data:1001101001110011011111100100 S0 Q=3x3x3x3x3x3x3x3x3x3x3x2x2=708588 7 4 6 5 1 2 3 Secret data: (011011111100100)2(473060)10 C7 C6 C4 C3 C2 473060th combination 7 4 5 1 6 2 3

Experimental Results Host Images Stego Images

Table 1. Embedding performance 41.26 40265 41.12 21405 (f) Garfield-b 40.24 12104 40.65 8168 (e) Garfield-a 42.24 17472 42.22 10349 (c) CCU-Upbar 42.84 5631 42.90 4333 (b) CCU-Logo 40.07 7342 40.04 6160 (d) Palette 41.67 PSNR 40.75 38102 Capacity Our proposed method 20012 (a) Midnight Tzeng et al’s method Schemes Images

Table 2. Embedding capacity and image quality 35.13 145543 70 35.06 60805 62 36.44 17442 23 37.08 61980 9 35.48 59687 16 36.35 179014 36 39.94 63576 188 39.82 20022 200 39.33 10112 29 39.84 46991 22 38.20 33133 40 38.33 112173 115 36.24 124237 110 35.67 57091 107 36.50 17299 24 37.40 70350 11 36.90 44445 37.15 133010 60 35.83 139762 79 35.73 54939 71 36.81 74971 58737 17 36.51 170356 41.26 40265 255 19158 40.40 5893 31 41.48 36568 41.90 7126 41.67 38102 215 39.25 73269 152 39.36 22766 160 39.41 12814 27 37.68 68556 18 37.94 35426 30 38.26 110847 92 40.04 59336 253 39.83 19196 254 40.07 7342 40.82 42630 40.23 22003 49 39.77 73681 155 36.10 128344 91 35.69 56021 88 36.70 77798 35.74 58077 21 36.43 179387 45 36.76 112435 127 36.53 46450 125 38.76 11431 26 37.49 69792 14 36.98 43391 28 37.19 136081 72 PSNR Capacity Clusters (f) Garfield-b (e) Garfield-a (d) Palette (c) CCU-Upbar (b) CCU-Logo (a) Midnight

Conclusions An adaptive data hiding scheme for the palette images. High embedding capacity and good image quality

Thank you very much for your attention !!