Download presentation
Presentation is loading. Please wait.
1
Digital Steganography Utilizing Features of JPEG Images
Author：Motoi IWATA, Kyosuke MIYAKE, Akira SHIOZAKI Source：IEICE Transactions on Fundamentals, Vol. E87-A No. 4, pp , APRIL 2004 Speaker：Yu-Cheng Wang Date：2004/05/27
2
Outline Introduction JPEG Compression (baseline sequential coding)
Embedding and Extracting method Experimental Results Conclusions
3
Introduction Embed Secret information network JPEG Image File Extract
4
JPEG Compression (baseline sequential coding)
16 Y Cb Cr 8 MCU
5
Proposed method quantization table DCT quantization 99 105 112 98 95
92 72 114 89 75 68 64 49 111 109 42 39 35 24 60 62 44 34 29 22 18 52 48 36 25 14 58 28 16 13 38 12 11 61 51 40 10 quantization table 152 155 161 166 170 164 173 163 159 190 209 185 169 172 162 168 213 244 204 158 171 222 254 206 167 226 188 179 165 160 177 175 183 187 176 178 194 DCT 24 -3 -6 2 -1 1 -2 -4 5 386 -29 -62 25 55 -20 -1 2 6 -21 8 12 -7 -6 7 -46 77 -26 -30 10 -5 -49 34 -14 -10 1 11 -8 -12 -2 3 -3 -4 quantization
6
Proposed method Embedding Procedure Each Di embeds one bit. D3 D5 D7
q11 q12 q13 q14 q15 q16 q17 q18 Di: The set consists of quantized DCT coefficients on the line. (1 <= i <= Lb) D2 q21 q22 q23 q24 q25 q26 q27 q28 D4 q31 q32 q33 q34 q35 q36 q37 q38 Lb: The number of bits embedded in a block. D6 q41 q42 q43 q44 q45 q46 q47 q48 ri: The length of a zero sequence of higher frequency components on the Di. D8 q51 q52 q53 q54 q55 q56 q57 q58 q61 q62 q63 q64 q65 q66 q67 q68 Pi: The non-zero value of the highest frequency component. q71 q72 q73 q74 q75 q76 q77 q78 q81 q82 q83 q84 q85 q86 q87 q88 Lb = 9 D1 = {q22, q33, q44, q55, q66, q77, q88} = {-2, 3, 0, 0, 0, 0, 0} r1 = 5 p1 = 3 Quantized Block Each Di embeds one bit.
7
Proposed method Embedding Procedure (cont.)
We change the length of zero sequence of higher frequency components (ri) according to information bit. If information bit is 1, the ri must be odd. If information bit is 0, the ri must be even. If information bit is 1 and the ri is even, or if information bit is 0 and the ri is odd, we must modify ri.
8
Proposed method Embedding Procedure (cont.) T=1
(2) If |pi| <= T and upper left coefficient of pi exists and is zero (3) If |pi| <= T and upper left coefficient of pi does not exist or is non-zero (4) If pi does not exist (only zeros exist in the set Di) (1) If |pi| > T 5 3 5 1 5 4 1 5 3 1 5 1 5 4 1 (or –1) (or –1)
9
Proposed method Example: T=1 L=0 1 1 0 0 0 1 0 1 D3 D1 D2 24 -3 -6 2
-1 1 -2 -4 5 24 -1 -3 -4 -6 1 2 1 2 D2 1 2 -2 5 1 -3 1 -4 L=
10
Proposed method Extracting Procedure 1 1 1 1
24 -3 -6 2 -1 1 -2 -4 5 1 1 1 1 We can embed Nx*Ny*Lb/64 bits.
11
Proposed method Expansion of the proposed method First method: α= 3
g2 First method: g1 α= 3 24 -3 -6 2 -1 1 -2 -4 5 23 -3 g3 zig-zag scan order Embedding information: 110 Embedding method: Embedding 0: the ge value is even. Embedding 1: the ge value is odd. Modified method: If ge is zero: 1 or -1 If ge is non-zero: decrease ge by 1. We can embed Nx*Ny*(α+2*β)/64 bits.
12
Proposed method Expansion of the proposed method Second method:
qj: The sum of the absolute values of quantized DCT coefficients in the set Dj. (1<=j<=Ls) D3 D5 D7 D9 D1 q11 q12 q13 q14 q15 q16 q17 q18 D2 Ls: The number of bits embedded in a block. q21 q22 q23 q24 q25 q26 q27 q28 D4 q31 q32 q33 q34 q35 q36 q37 q38 D6 Embedding method: Embedding 0: the qj value is even. Embedding 1: the qj value is odd. q41 q42 q43 q44 q45 q46 q47 q48 D8 q51 q52 q53 q54 q55 q56 q57 q58 q61 q62 q63 q64 q65 q66 q67 q68 q71 q72 q73 q74 q75 q76 q77 q78 Modified method: If |qj|>1: decrease the lowest coefficient by 1. If |qj|=1: increase |qj| by 1. If qj dose not exist: the secondly lowest coefficient is replaced with –1 or 1. q81 q82 q83 q84 q85 q86 q87 q88 Quantized Block We can embed Nx*Ny*Ls/64 bits.
13
Proposed method Expansion of the proposed method
Second method: (Example) 23 -3 -6 2 -1 -2 -4 1 5 |-1|=1 23 -3 -6 2 -1 -2 -4 1 5 -2 |-2|+|5|+|1|=8 -3 1 Ls = 11 |0| = 0 L=
14
Proposed method Combined method α= 3 Combined method:
ge α= 3 Di Combined method: L’=Nx*Ny(Lb+α+2*β +Ls)/64
15
Experimental Results Color images: 256 x 256 pixels Ability of Embedding: The ratio of the number of embedded bits to the size of a JPEG stegoimage.
16
Experimental Results
17
Experimental Results
18
Conclusions A novel steganographic method utilizing the feature of quantized DCT coefficients obtained by JPEG compression. The advantage is the difficulty of detecting the existence of secret information. The advantage is derived from using the modification similar to JPEG compression.
Similar presentations
