Reporter :Chien-Wen Huang Date : Information Sciences, Vol. 176, No. 22, Nov. 2006, pp Received 29 December 2004; received in revised form 24 January 2006; accepted 3 February

1. Introduction 2. Related Work 3. The Proposed Methods  Hiding bitmap files  Hiding general data files 4. Experimental Results 5. Discussion and Conclusions 2

The most well-known steganographic technique-LSB. RLE (Run-Length Encoding)  Compression standard in fax transmissions and bitmap-file coding. Two efficient data hiding methods by run-length encoding.  BRL and GRL 3

 Wu and Tsai’s steganographic method 4

 Chang and Tseng’s steganographic method 5

RLE  Example1 : AAAAABBBBAA 5A4B2A  Example2:

 The host image is partitioned into non-overlapping consecutive two-pixel blocks by zigzag scanning. 7

Hiding bitmap files  BRL hides the run value in and the run count in.  The range that the remainder of modulo k falls in – namely from 0 to (k-1) Thus,the definition of sign is as follows: 8

 The hiding process of BRL is formulated as follows:  The extraction scheme is as follows: 9

 Example:k=5, hiding secret bits: (3,1) (5,0) (4,1) (V 1, C 1 ) = (12, 8), (V 2, C 2 ) = (2, 3), (V 3, C 3 ) = (240, 254). [LSB match] 1.8 -> 3 =8+x mod k = 3-1 x=-1 or 4 [LSB replace] > 1 =12+1=13 RLE 10

Hiding general data files  In GRL, the value of is the number of 1’s in, and the value of is the sequential order of combinations by.  The following mapping function f, where is set to be zero if n is smaller than k : 11

 the value of can be obtained from using  The recursive function : 12

 Example: Six secret bits are to be embedded in the pair of original pixels (43, 58) N(1)=1,N(2)=1,N(3)=2,N(4)=2,N(5)=

 The extraction process of (45,53) and n= S 5 S 4 S 3 S 2 S 1 S 0 s 0 :s 5 s 5 =C(5,3)=10<13  ’1’ num =13-10=3 14 s 0 :s 4 s 4 =C(4,2)=6>3  ’0’ s 0 : s 3 s 3 =C(3,2)=3 ≦ 3  ’1’ num = 3-3 = 0 s 0 :s 2 s 2 =‘0’ ; s 0 :s 1 s 1 =‘0’, s 0 =‘1’

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Comparison of PSNR and capacities using Lena as the cover image. 17

Comparison of PSNR and capacities using Baboon as the cover image. 18

No need to refer to the original image during the extraction process. Probably be extended to embedding secret data in compressed images using VQ or JPEG techniques. 19