Data Hiding in binary images using

block parity

Group ID -17Guided by Mr. Pramod Ganjewar

By – Sipendra Sinha Deepak Kumar Rohit Singh Amol Gaikwad Snehal Darade

Outline• Introduction• Algorithm

Embedding AlgorithmExtraction Algorithm

Checking visibility due to bit changedBinary File specificationsImplementation Details and ResultApplications Conclusion

Algorithm

Partitioned block

Calculating characteristic

value

Data retrieving

Data hiding

Partitioned block

Calculating characteristic

value

Secret data

Original image

Stego-image

Stego-image

Secret data

Flow for data hiding and retrieving

Checking visibility of change

Binary File Specifications PBM or Portable Bitmap is used. Binary format is used as it uses 1 bit per

pixel.

.

Embedding AlgorithmStep 1:Divide the cover image into blocks

of 5 X 5

Embedding AlgorithmStep 2: For each block, except single-value

black and white ones, proceed as follows: 1. X-OR all 4 rows and 4 columns.

r1=1 c1=0

r2=0 c2=0r3=0 c3=1r4=0 c4=1

Embedding Algorithm2. X-OR the results in 1 and 2 to get

s1,s2,s3,s4 where s1=r1⊕c1, s2=r2⊕c2, and so on.

s1= r1⊕ c1= 0⊕1=1 s2= r2⊕ c2= 0⊕0=0s3= r3⊕ c3= 0⊕1=1s4= r4⊕ c4= 0⊕1=1

Embedding Algorithm

3. Compare the result obtained from 3 with the four embedded bits b1b2b3b4. If there is no difference, no change of bits in F is needed, otherwise, consider the following cases:

a)If the difference in one bit bi, the bit [F] i,5 or [F]5,i should be changed.

b)else if difference in two bits bi and bj, then the bit [F] i,j or [F]j,i should be changed.

.

c)else if difference in three bits bi, bj and bk, then the bits

(( [F] I,j or [F] j,i) and ( [F]k,5 or [F]5,k)) or

(( [F] i,5 or [F] 5,i) and ( [F] k,j or [F] j,k)) or

(( [F] 5,j or [F] j,5) and ( [F] k,i or [F] I,k))

should be changed

d)else difference in four bits then

(( [F] i,j or [F] j,i) and ( [F]k,m or [F]m,k)) or

(( [F] i,m or [F] m,i) and ( [F]k,j or [F]j,k)) or

(( [F] m,j or [F] j,m) and ( [F]k,i or [F]i,k)) should be changed

Embedding Algorithm4.

Here we have 3 bits difference,

So third criteria is selected and

Fi,j or Fk,5 are changed.

After hiding data in a 5*5 block is :

Fig. Block image after hiding data

Extraction Algorithm

IInput : Stego-Image

Output : Secret message

The step envolve in the Extraction Algorithms are:-

Step1: Divide the cover image into blocks (F) each of size 5×5.

Fig.Stego-block

Step2: For each block, except single-value black and white ones, proceed as follows:

1.For every row in the first four rows of the block,exclusive-or all the bits of that row to get

r1,r2,r3 and r4.2.For every column in the first four columns of the block, exclusive-or all the bits of that column to get

c1,c2,c3 and c4 is given bellow.

3.Exclusive-or the results in 1 and 2 to get the embedded bits s1,s2,s3,s4 where S1 = r1 XOR c1,S2 = r2 XOR c2,S3 = r3 XOR c3,S4 = r4 XOR c4 .

S1 = r1 XOR c1 = 0 XOR 0 = 0

S2 = r2 XOR c2 = 0 XOR 1 = 1

S3 = r3 XOR c3 = 1 XOR 1 = 0

S4 = r4 XOR c4 = 0 XOR 1 = 1

a) Embedded data b) Extracted data

Snapshot of Result1 ASCII representation - Input image

E:\work\Java>java hiding

--- Data Hiding ---

13 bytes can be hidden

Enter text string to be hidden :

image23

2 ASCII representation –Output image

2 ASCII representation – Output image

E:\work\Java>java extraction

--- Data extraction ---

image23

7 bytes of data successfully extracted !!

Implementation Details and ResultEmbedding

E:\work\Java>java hiding--- Data Hiding ---

3618 bytes can be hidden

Enter text string to be hidden :the quick brown fox jumped over the wolf

40 bytes of data successfully hidden !!

Fig. Cover-image

No. of blocks in Binary image = 10404

No. of blocks available for hiding = 7236

Hiding capacity of 1 block = 4 bit

Hiding capacity of given binary image = 7236/2 =3618 byte

Hiding capacity of given image = 3.53 KB

Hiding factor = =(7236/10404) X 100

= 69.55 %

Extraction

E:\work\Java>java extraction

--- Data extraction ---

the quick brown fox jumped over the wolf

40 bytes of data successfully extracted !!

Fig. Stego-image

3 Comparison of original image with result

Fig. 1 Cover-image Fig. 2 Stego-image

Applications

FAXAdding captions to imagesCopyright protection of digital images

(authentication)Image integrity protection (fraud

detection)Covert Communication -To conceal the

very presence of communication, to make the communication invisible.

Conclusion

Using this method of hiding data in binary images,at max 2 bits are changed in a block of 5X5 for hiding 4 bit data in it.As only 12 XOR operations are needed for hiding and extraction of data,the computational time is very less. Binary images are used in sending FAX,so using scanning technique,data can be extracted from hard copy of images in FAX.

References

Data Hiding In A Binary Image by Ahmed Al-Jaber and Khair Eddin Sabri Department of Computer Science King Abdullah II School for Information Technology (KASIT) University of Jordan

N. Johnson and S. Jajodia, “Exploring steganography: seeing the unseen,” IEEE Computer,

pp. 26-34, February 1998.

QUESTIONS ?