CHAPTER 3 INFORMATION HIDING USING LEAST...

Information Hiding in Image and Audio Files 2007-2010

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CHAPTER 3

INFORMATION HIDING USING LEAST

SIGNIFICANT BIT METHOD

The Least Significant Bit (LSB) insertion method is a common,

simple approach to embedding information in a graphical image file.

In LSB insertion method the LSB of every pixel is replaced by every

message bit. There is 50 % chance that the message may match

with the LSB‟s of the Cover image. Thus only 50 % LSB‟s are likely

to change. Also, the change occurs only in the bit which is least

significant, thus keeping the other more significant bits unaltered.

Therefore, this does not affect the original image perceptibility.

Hence it is a very popular technique. However, it is extremely

vulnerable to attacks. Any image manipulations such as cropping,

intensity changes for any enhancements such as contrast

stretching, histogram equalization, addition of noise etc will destroy

the embedded message.

The techniques other than LSB technique are complicated, although

they are robust to most attacks. LSB technique can therefore be

used wherever we want to store confidential information on a

standalone PC or one which is shared among several users. LSB

technique can be used to store personal data such as ATM PIN,

Credit card details, salary statement, income tax data, passport

information etc in an imperceptible way. So, wherever this kind of

information is to be preserved in a manner that only legitimate user

should be able to retrieve it whenever needed, by simple ways, LSB

is a better solution.

Least Significant Bit (LSB) encoding is the easiest of the techniques

used for embedding secret or confidential information in digital


42

images. For a gray scale bitmap (BMP), using the LSB of each byte

(8 bits) in an image, a secret message of size 1/8th of the Cover

image can be stored. This can be easily done by directly substituting

every bit of the secret message into every LSB.

For a 24 bit color image as the cover image, since there are 3 bytes

for every pixel, 3 bits of data can be stored in each pixel, so the

capacity to store increases by 3 times thus making it 3/8 of the

cover image size. If the message to be embedded is a text message

a secret message of size 1/7th of the grayscale cover image can be

stored and in a 24 bit color image as cover a text message of size

3/7 can be embedded.

The confidential information which is embedded in the Cover image

can be an image (grayscale, binary or color image), text or even

audio. As the type and size of confidential information varies, the

embedding capacity varies for a particular type of Cover used. LSB

technique can be used either by directly replacing the Cover LSB‟s

by the Secret information bits, or to add one more level of security,

it can be encrypted and then inserted into the LSB‟s of the Cover.

3.1 Using 2 / 3 / n LSB’s Technique

The technique [79] implemented in this section not only replaces

the LSB, but the LSB is modified by taking into consideration the

other bits of the Cover and the message bit as well. Advantage of

this method is it adds one more level of security, by encrypting the

message bits before embedding with just a slight increase in the

encoding / decoding complexity and Cover capacity remains the

same as LSB substitution, accuracy of retrieval is 100%, and good

perceptual transparency of cover image is achieved.


43

3.1.1 Embedding Algorithm

Extract RGB components of pixel intensity values of message and

the cover image if 24 bit color images are to be used else for a

grayscale image every byte is the intensity of every pixel. In case

text message is to be embedded, then their ASCII codes have to be

considered. The procedure given below is by considering 24 bit color

images. Take the successive R, G, and B component values of pixels

and convert them into array of values for messages and the cover

image. Convert every decimal value into 8 bit binary equivalent for

cover and message images. Every message bit is embedded into

LSB‟s of the cover image after processing. Processing is done as

follows:

a) LSB 2 Method:

If the message bit to be embedded is 0, then adjust the LSB

such that the XOR operation on LSB and next to LSB is 0 and

if the message bit to be embedded is 1, then adjust the LSB

such that the XOR operation on LSB and next to LSB is 1 as

shown in the Table 3.1 below.

Table 3.1 Truth Table for LSB 2 Bit Method

Next to LSB LSB Message Bit LSB Adjusted

0 0 0 No Change

0 1 0 0

1 0 0 1

1 1 0 No change

0 0 1 1

0 1 1 No change

1 0 1 No change

1 1 1 0

Remark: There are 50 % chances that there will not be any change in the

Stego.

b) LSB 3 Method: If the message bit to be embedded is 1, then

the LSB is adjusted such that the XOR operation on LSB, next


44

to LSB and next to next to LSB is 0. And if the message bit to

be embedded is 1, then adjust the LSB such that the XOR

operation on LSB next to LSB and next to next to LSB is 1 as

shown in the Table 3.2 below.

Table 3.2 Truth Table for LSB 3 Bit Method

Next to Next LSB

Next to LSB

LSB Message Bit

LSB Adjusted

0 0 0 0 No change

0 0 1 0 0

0 1 0 0 1

0 1 1 0 No change

1 0 0 0 1

1 0 1 0 No change

1 1 0 0 No change

1 1 1 0 0

0 0 0 1 1

0 0 1 1 No change

0 1 0 1 No change

0 1 1 1 0

1 0 0 1 No change

1 0 1 1 0

1 1 0 1 1

1 1 1 1 No change

The message embedding in the cover image is over.

3.1.2 Retrieving Algorithm

The message retrieving is done as per the algorithm given below

a) Extract Red, Green and Blue Components of pixel intensity

values of Stego image.

b) Take successive Red, Green and Blue component values of

pixels and convert them into array of values for message and

Stego image.

c) Convert every decimal value into 8 bit binary equivalent for

Stego image.

d) Retrieval of the message bit is done by using the XOR

operation on the LSB and Next to LSB.

i. If it is 1 then message bit is 1.

ii. If it is 0 then message bit is 0.


45

e) If during embedding the LSB 3 method is used then retrieval

is done by performing XOR operation on LSB, next to LSB and

Next to Next to LSB‟s.

i. If the result of XOR operation is 0, it means the decoded

message bit value is 0 and

ii. If the result is 1, it means that the decoded message bit

value is 1.

f) Convert every 8 bits to form a byte whose decimal value is

the pixel intensity if the message embedded is a grayscale

image otherwise this decimal value forms the intensity of Red

component of the first pixel of the Secret image, if the

message embedded is a 24 bit color image. If the message

that is embedded is a text message then after every 7 bits are

retrieved convert them into decimal which forms the ASCII

code of the 1st character. In this manner these steps are

continued till the full message is retrieved.

g) In case of 24 bit, every byte forms either the Red, Green or

Blue component of the message pixels in sequence. Take 3

bytes and group them as 3 RGB components of a 1 pixel.

Perform this step for the full message.

The message retrieval is over.

Instead of only 2 or 3 LSB‟s this method can be extended till all the

8 bits of the cover image are considered to encrypt the message bit,

and then in that case the decryption will be done considering 2, 3

till 8 bits of the Cover image respectively.

3.2 Considering Parity

In addition to the above encryption method, one more simple

method for encryption is suggested, which uses parity as a key for


46

embedding. The embedding and retrieval is to be done as given

below.

3.2.1 Embedding Algorithm [80]:

Adjust the LSB of the byte of the Cover so that it is even parity after

embedding if the message bit to be embedded is 0 and adjust the

LSB of the byte of the Cover so that it becomes odd parity after

embedding of if the message bit to be embedded is 1. This is done

till the embedding of all message bits is over.

3.2.2 Retrieval Algorithm:

For retrieving the message the Stego image is taken. The parity of

every byte is checked. If the parity is even that means the message

bit is 0 and if the parity is odd it means the message bit is 1. The

role of odd and even parity is interchangeable.

In this way after 8 such message bits are retrieved they are

converted to decimal and this decimal number becomes the

intensity value of the first message pixel for grayscale image or Red

component of the first pixel if the message is 24 bit color image. If

the message embedded was a text message, then after every 7 bits

of message are retrieved they are converted to decimal and this

decimal value is the ASCII code of the 1st character in the message.

This procedure is repeated until the full message is retrieved, and

the message image is formed or the full text message is retrieved.

3.3 Experimental Results

For Experimental purpose, 2 sets (24 bit colour) of fifteen cover

images each, one set of size 512 X 512 and the other of size 1024 X

1024 for all the three methods (LSB 2, LSB 3 and Parity) are used.


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Ten secret message images and 4 Microsoft word documents are

used for embedding. The 10 message images are 128X128, 24-bit

color images and out of the four Microsoft word documents 1st is the

speech delivered by Dr. A. P. J. Abdul Kalam in Hyderabad which is

3 pages Microsoft Word document of 1262 words (6764 characters),

2nd message is the famous Abraham Lincoln‟s letter to his son‟s

teacher which is 1 page letter of 396 words (1988 characters), the

3rd is a 7 page Microsoft word document which is the 5th chapter

from „The Tale of two cities‟ with 4171 words, and 23496

characters, and the 4th message is the front page of my Synopsis

Report with NMIMS logo which is a 1 page Microsoft Word document

with 78 words and 486 characters.

All cover images, message images and text messages are given in

appendix. The Experimental results obtained for some of the Cover

images, Stego Images are shown in Figure 3.1 (a-d) to 3.8 (a-d).

Figure 3.1(a) - Figure 3.4(a) represent 24 bit cover images of size

512 X 512. Figure 3.1(b) - Figure 3.4(b) represent their stego

images using LSB 2 XOR method, Figure 3.1(c) - Figure 3.4(c)

represent their stego images using LSB 3 XOR method, Figure

3.1(d) to Figure 3.4(d) represent their stego images using LSB

parity method respectively with message image 1 embedded in it.

Figure 3.5(a)-3.8(a) are Cover images of size 1024 X 1024. Figure

3.5(b) - 3.8(b) are Stego images using LSB 2 bit XOR algorithm

Figure 3.5(b)- 3.8(b) are Stego images using LSB 3 bit XOR

algorithm and Figure 3.5(d)-3.8(d) are Stego images using LSB

parity method with message 1 embedded in it.

Figure 3.9 (a) shows the message image 1 which is used as input

message. Figure 3.9(b) - Figure 3.9(d) shows the retrieved

message from Stego image which are shown in Figure 3.1(b)-Figure


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3.1(d). The message retrieval is 100% for all three methods and so

message retrieved from only 1 Stego image for all three methods is

shown over here

Figure 3.1(a) Figure 3.1(b) Figure 3.1(c) Figure 3.1(d)

MSE = 0.252 MSE = 0.251 MSE = 0.250


MSE = 0.251 MSE = 0.251 MSE = 0.250


MSE=0.243 MSE = 0.256 MSE = 0.248


MSE=0.252 MSE = 0.250 MSE = 0.238

Cover images of size 512 X 512

Stego images for LSB2 with message1


Stego images for LSB Parity with

message1


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MSE = 0.063 MSE = 0.063 MSE = 0.060


MSE=0.063 MSE = 0.062 MSE = 0.062


MSE=0.060 MSE=0.065 MSE=0.065


MSE=0.062 MSE=0.061 MSE=0.062

Cover images of size 1024 X 1024



Stego images for LSB Parity with

message1


Original Message Message retrieved from Stego 3.1(b)

Message retrieved from Stego 3.1(c)

Message retrieved from stego 3.1(d)


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A new parameter AFCPV is introduced which gives a better feel of

perceptibility as compared to MSE.

Since Perceptibility is one of the major aspects of steganography,

the parameter introduced gives a measure to this aspect. Smaller

the value of AFCPV, better is the imperceptibility

NxM

)f / |f -f(|AFCVP

yx,yx,yx,

where fx,y :original image, f‟x,y : stego image.

M: number of rows N : number of columns

in the input images

For performance evaluation of different methods the parameters

used are Mean Squared Error (MSE), Peak Signal to Noise Ratio

(PSNR), Average Fractional Change in Pixel Value (AFCPV),

Percentage of Bytes Changed, Percentage change in LSB‟s (from

Zero to One and One to Zero.

Mean Square Error (MSE)

The MSE represents the cumulative squared error between the

decompressed/reconstructed and the original image. MSE between

two images can be computed as,

NM

)n,m(I)n,m(I

MSE N,M

221

where


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M and N : number of rows and columns in the input images,

respectively.

I1 (m,n) :image pixel value at position (m,n) in the original image

I2(m,n) is the image pixel value at position (m,n) in the stego

image.

Lesser the MSE, better the quality of reconstructed image.

Peak Signal to Noise Ratio (PSNR)

PSNR represents a measure of the peak error. The higher the PSNR,

the better the quality of the decompressed or reconstructed image.

PSNR is computed as,

MSE

Rlog10PSNR

2

10

R is the maximum fluctuation in the input image data type. For

example, if the input image has a double-precision floating-point

data type, then R is 1. If it has an 8-bit unsigned integer data type,

R is 255.

Percentage of Bytes Changed (PBC)

Another useful parameter which is used to measure the quality of

the reconstructed image is Percent of Bytes changed [35]. Lesser

the value, better the reconstructed image.


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Percentage of Bytes changes is computed as

100*Bytesof.NoTotal

changedBytesof.NoP

Retrieval Accuracy (RA)

This parameter is used to measure the retrieval accuracy of the

secret message from stego image.

100*Bytesof.NoTotal

eredcovreBytescorrectof.NoA

(3.13)

The Tables and Charts for the all the algorithms are shown below.

Table 3.3 shows the values of MSE, PSNR, AFCPV, Percentage of

bytes changed, Changes (0 to 1) in percent and Changes (1 to 0) in

percent for embedding a message image of an ATM Card

(Message1) in Cover images 1 -15 of size 512 X 512 using LSB 2-bit

Method. The last row shows their average values for Cover images

1- 15.

Table 3.4 shows the average values of MSE, PSNR, AFCPV,

Percentage of bytes changed, Changes (0 to 1) in percent and

Changes (1 to 0) in percent for Cover images 1 - 15 of size 512 X

512 using LSB 2-bit Method with 10 different message images

embedded in them.


53

Table No 3.3 Values of MSE, PSNR, AFCPV, bytes changed , Changes (0 to 1) in

percent and Changes (1 to 0) in percent for embedding a message image of an ATM Card (Message1) in Cover images 1 -15 of size 512 X 512 using LSB 2-bit Method

Cover Image

Message MSE PSNR (db)

AFCPV

Percent Change

Change (0 to 1) in %

Change (1To 0) in %

CV1 1 0.252 54.114 0.651 25.214 12.760 12.454

CV2 1 0.252 54.122 0.267 25.170 12.458 12.712

CV3 1 0.251 54.137 0.341 25.085 12.558 12.527

CV4 1 0.242 54.294 0.287 24.191 11.367 12.823

CV5 1 0.256 54.056 0.168 25.555 12.206 13.349

CV6 1 0.257 54.033 1.478 25.691 13.905 11.786

CV7 1 0.249 54.161 1.093 24.944 12.505 12.439

CV8 1 0.321 53.067 0.417 32.090 25.726 6.364

CV9 1 0.252 54.108 0.308 25.249 12.797 12.452

CV10 1 0.229 54.535 0.420 22.885 6.679 16.206

CV11 1 0.252 54.110 0.197 25.237 12.226 13.012

CV12 1 0.372 52.431 0.144 37.151 0.422 36.729

CV13 1 0.257 54.030 0.228 25.707 12.855 12.851

CV14 1 0.233 54.463 0.413 23.266 9.418 13.849

CV15 1 0.269 53.839 0.564 26.867 11.429 15.438

Average

0.263 53.967 0.465 26.287 11.954 14.333

Table No 3.4 Average values of MSE, PSNR, AFCPV, Total bytes changed , Changes (0 to 1) and Changes (1 to 0) in percent for embedding 10 message images 1-10

in Cover images cvimg1 - cvimg15( 512 X 512) using LSB 2-bit Method

Message MSE

PSNR (db)

AFCPV Percent Change

% change ( 0 To 1)

% change (1To 0)

1 0.263 53.967 0.465 26.287 11.954 14.333

2 0.260 53.996 0.475 26.033 12.026 14.007

3 0.254 54.086 0.493 25.401 11.842 13.559

4 0.242 54.314 0.512 24.160 11.864 12.296

5 0.258 54.031 0.473 25.791 11.972 13.819

6 0.266 53.927 0.452 26.624 11.954 14.671

7 0.260 54.004 0.467 25.996 12.052 13.944

8 0.258 54.018 0.488 25.850 11.987 13.863

9 0.261 53.994 0.472 26.051 12.010 14.041

10 0.248 54.196 0.512 24.756 11.833 12.923

Remark: It is observed that the maximum AFCPV is 0.512 and maximum Average

Percentage change is 26.624 with LSB2 method for Cover of size 512X512

Similarly Table 3.5 shows the values of MSE, PSNR, AFCPV,

Percentage of bytes changed, Changes (Zero to One) in percent and

Changes (One to Zero) in percent for embedding a message image

of an ATM Card (Message1) in Cover images 16 -30 of size 1024 X

1024 using LSB 2-bit Method. The last row shows their average

values for Cover images 16 – 30


54

Table No 3.5 Values of MSE, PSNR, AFCPV, bytes changed , Changes (0 to 1) and

Changes (1 to 0) in percent for embedding a message image of an ATM Card

(Message1) in Cover images 16 -30 of size 1024 X 1024 using LSB 2-bit Method

Cover Image


AFCPV Percent Change

Change (0 to 1) in %

Change (1To 0) in %

CV16 1 0.065 60.026 0.066 6.464 3.218 3.246

CV17 1 0.064 60.038 0.043 6.446 2.467 3.979

CV18 1 0.062 60.182 0.097 6.236 3.190 3.046

CV19 1 0.064 60.101 0.036 6.353 3.198 3.155

CV20 1 0.062 60.192 0.066 6.221 3.031 3.190

CV21 1 0.065 59.998 0.276 6.505 3.496 3.009

CV22 1 0.093 58.452 0.036 9.288 0.000 9.288

CV23 1 0.064 60.069 0.070 6.400 2.684 3.716

CV24 1 0.088 58.710 0.046 8.751 8.189 0.562

CV25 1 0.063 60.162 0.076 6.264 3.089 3.175

CV26 1 0.062 60.190 0.036 6.224 3.145 3.080

CV27 1 0.068 59.832 0.055 6.759 3.540 3.220

CV28 1 0.060 60.351 0.044 5.998 2.571 3.428

CV29 1 0.090 58.584 0.035 9.010 0.000 9.010

CV30 1 0.063 60.124 0.035 6.320 2.827 3.493

Average 1 0.069 59.801 0.068 6.883 2.976 3.906


Percentage of bytes changed, Changes (0 to 1) and (1 to 0) in

percent for Cover images 16 - 30 of size 1024 X 1024 using LSB 2-

bit Method with 10 different message images embedded in them.

Table No 3.6 Average values of MSE, PSNR, AFCPV, Total bytes changed , Changes (0 to 1) and (1 to 0) in percent for 10 message images in Cover images 16 - 30 of size 1024 X 1024 using LSB 2-bit Method


AFCPV % change % change (0- 1)

% change (1- 0)

1 0.069 59.801 0.068 6.883 2.976 3.906

2 0.067 59.891 0.068 6.714 2.939 3.775

3 0.066 59.976 0.071 6.555 2.896 3.658

4 0.060 60.387 0.072 5.984 2.775 3.208

5 0.067 59.889 0.068 6.706 2.968 3.738

6 0.071 59.693 0.067 7.092 3.053 4.039

7 0.068 59.867 0.068 6.750 2.963 3.787

8 0.066 59.985 0.069 6.556 2.886 3.670

9 0.068 59.858 0.068 6.770 2.973 3.797

10 0.062 60.183 0.072 6.238 2.837 3.401


Percentage change is 7.092 with LSB2 method for Cover of size 1024 X 1024


55

Figure 3.10 and Figure 3.11 show the average MSE values, Figure

3.12 and Figure 3.13 show the average PSNR values, Figure 3.14

and Figure 3.15 show the average AFCPV values and Figure 3.16

and Figure 3.17 show the average changes Total bytes changed,

changes (0-1) and changes (1-0) in percent using LSB-2 algorithm

for Cover size 512 X 512 and 1024 X 1024 respectively.

Figure 3.10 Average MSE value for 15

Cover images of (512X512) using LSB-2

algorithm for embedding 10 different

images of size 128X128

Figure 3.11 Average MSE for 15 Cover

images (1024X1024) using LSB-2


message images of size 128 X 128

Figure 3.12 Average PSNR for Cover

images 1-15 of size 512 X 512 using LSB-

2 algorithm for embedding 10 different

message images (128 X 128)


images 16-30 of size 1024 X 1024 using

LSB-2 algorithm for embedding 10

different message images (128 X 128)

0.2630.260

0.254

0.242

0.258

0.266

0.2600.2580.261

0.248

0.2250.2300.2350.2400.2450.2500.2550.2600.2650.270

MSE : LSB 2 Algorithm Cover 512 X 512

MSEC

0.06880.0671

0.0655

0.0598

0.0671

0.0709

0.06750.0656

0.0677

0.0624

0.05400.05600.05800.06000.06200.06400.06600.06800.07000.0720

MSE : LSB 2 Algorithm Cover 1024X 1024

MSEC AVG MSE = 0.066

53.9754.00

54.09

54.31

54.03

53.9354.0054.0253.99

54.20

53.70

53.80

53.90

54.00

54.10

54.20

54.30

54.40

PSNRC : LSB 2 Algorithm Cover 512 X 512

PSNRC AVG PSNR =54.05

59.8059.89

59.98

60.39

59.89

59.69

59.8759.98

59.86

60.18

59.20

59.40

59.60

59.80

60.00

60.20

60.40

60.60

PSNRC : LSB 2 Algorithm Cover 1024X1024



56

Figure 3.14 Average AFCPV for Cover


2 algorithm for 10 messages (128 X 128)


images of size 1024X1024 using LSB-2

algorithm for 10 messages (128 X 128)

Figure 3.16 Average values for total

change in percent. for Cover images 1-15

of size 512 X 512 using LSB-2 algorithm

for 10 message images (128 X 128)


change in percent. for Cover images 16-

30 of size 1024X1024 using LSB-2

algorithm for 10 messages (128 X 128)





embedded in them.

0.4650.475

0.493

0.512

0.473

0.452

0.467

0.488

0.472

0.512

0.4200.4300.4400.4500.4600.4700.4800.4900.5000.5100.520

AFCPV : LSB 2 Algorithm Cover 512 X 512

AFCPV AVG AFCPV=0.481

0.0680.068

0.0710.072

0.068

0.0670.068

0.0690.068

0.072

0.0640.0650.0660.0670.0680.0690.0700.0710.0720.073

AFCPV : LSB 2 Algorithm Cover 1024X 1024


26.2926.03

25.40

24.16

25.79

26.62

26.0025.8526.05

24.76

22.5023.0023.5024.0024.5025.0025.5026.0026.5027.00

% CHANGE : LSB 2 Algorithm Cover 512 X 512

Total % Change AVG % CHANGE=25.69

6.886.71

6.55

5.98

6.71

7.09

6.756.56

6.77

6.24

5.405.605.806.006.206.406.606.807.007.20

% CHANGE : LSB 2 Algorithm Cover 1024X 1024

Total % Change


57

Table No 3.7 Average values of MSE, PSNR, AFCPV, Percentage of bytes changed

and AFCPV for 10 message images in Cover images 1 -15 of size 512 X 512 using LSB 3-bit Method

Message Average

MSE Average PSNR (db)

Average AFCPV

Average% Change

Average % change (0 - 1)

Average% change (1- 0)

1 0.2512 54.191 0.489 25.12 13.02 12.10

2 0.2513 54.161 0.491 25.13 12.73 12.40

3 0.2485 54.183 0.502 24.85 12.20 12.65

4 0.2496 54.171 0.505 24.96 11.36 13.60

5 0.2513 54.151 0.492 25.13 12.57 12.56

6 0.2513 54.239 0.484 25.13 13.19 11.94

7 0.2520 54.151 0.486 25.20 12.77 12.43

8 0.2500 54.168 0.498 25.00 12.59 12.42

9 0.2514 54.162 0.491 25.14 12.79 12.36

10 0.2478 54.192 0.509 24.78 11.72 13.06







embedded in them.


and AFCPV for 10 message images in Cover images 16 - 30 of size 1024 X 1024 using LSB 3-bit Method

Message Average MSE

Average PSNR(db)

Average AFCPV

Average %

change

Average % change

(0- 1)

Average % change

(1- 0)

1 0.0604 60.43 0.0646 6.04 3.06 2.98

2 0.0607 60.36 0.0659 6.07 2.99 3.08

3 0.0618 60.23 0.0691 6.18 2.91 3.27

4 0.0636 60.12 0.0730 6.36 2.70 3.66

5 0.0611 60.31 0.0661 6.11 2.96 3.16

6 0.0597 60.57 0.0631 5.97 3.10 2.87

7 0.0608 60.35 0.0655 6.08 2.98 3.10

8 0.0614 60.28 0.0676 6.14 2.97 3.17

9 0.0607 60.36 0.0655 6.07 3.02 3.05

10 0.0629 60.15 0.0716 6.29 2.82 3.47



Figure 3.18 and Figure 3.19 show the average MSE values for Cover

size 512 X 512 and 1024 X 1024 respectively. Figure 3.20 and


58

Figure 3.21 show the average PSNR values, Figure 3.22 and Figure

3.23 show the average AFCPV values and Figure 3.24 and Figure

3.25 show the average changes i.e. Total bytes changed, in percent

using changes in percent using LSB-3 algorithm for Cover size 512

X 512 and 1024 X 1024 respectively.


Cover images of (512X512) using LSB-3


images of size 128X128


images (1024X1024) using LSB-3



Figure 3.20 Average PSNR(db) for Cover








0.2630.260

0.254

0.242

0.258

0.266

0.2600.2580.261

0.248

0.2250.2300.2350.2400.2450.2500.2550.2600.2650.270



0.0690.067

0.066

0.060

0.067

0.071

0.0680.066

0.068

0.062

0.0540.0560.0580.0600.0620.0640.0660.0680.0700.072

MSE : LSB 3 Algorithm Cover 1024X 1024


53.9754.00

54.09

54.31

54.03

53.9354.0054.0253.99

54.20

53.70

53.80

53.90

54.00

54.10

54.20

54.30

54.40

PSNRC : LSB 3 Algorithm Cover 512 X 512


59.8059.89

59.98

60.39

59.89

59.69

59.8759.98

59.86

60.18

59.20

59.40

59.60

59.80

60.00

60.20

60.40

60.60

PSNRC : LSB 3 Algorithm Cover 1024X1024

PSNRC AVG PSNRC =59.95


59






images 16-30 of size 1024X1024 using



Figure 3.24 Average values for total change, in percent. for 15 Cover images (512 X 512) using LSB-3 algorithm for embedding 10 images (128 X 128)

Figure 3.25 Average values for total change, in percent. for 15 Cover images (1024X1024) using LSB-3 algorithm for embedding 10 images (128 X 128)

Table 3.9 shows the average values of MSE, PSNR, AFCPV, and

Percentage of bytes changed, for Cover images 1 - 15 of size 512 X

512 using LSB Parity Method with 10 different message images

embedded in them.

0.4650.475

0.493

0.512

0.473

0.452

0.467

0.488

0.472

0.512

0.4200.4300.4400.4500.4600.4700.4800.4900.5000.5100.520



0.0680.068

0.0710.072

0.068

0.0670.068

0.0690.068

0.072

0.0640.0650.0660.0670.0680.0690.0700.0710.0720.073

AFCPV : LSB 3 Algorithm Cover 1024 X1024


26.2926.03

25.40

24.16

25.79

26.62

26.0025.8526.05

24.76

22.5023.0023.5024.0024.5025.0025.5026.0026.5027.00



6.886.71

6.55

5.98

6.71

7.09

6.756.56

6.77

6.24

5.405.605.806.006.206.406.606.807.007.20

% CHANGE : LSB 3 Algorithm Cover 1024X 1024



60


and AFCPV for 10 message images in Cover images 1 -15 of size 512 X 512 using LSB Parity Method

Message Average MSE

Average PSNR (db)

Average AFCPV

Average % change

Average % change (0- 1)


1 0.263 53.97 0.464 26.29 12.42 13.87

2 0.260 54.00 0.472 26.00 12.33 13.66

3 0.254 54.09 0.495 25.41 11.96 13.45

4 0.242 54.30 0.514 24.22 11.61 12.61

5 0.259 54.02 0.470 25.85 12.22 13.63

6 0.266 53.92 0.452 26.64 12.47 14.17

7 0.260 54.00 0.465 26.01 12.29 13.71

8 0.258 54.02 0.487 25.83 12.29 13.54

9 0.260 54.00 0.469 26.03 12.32 13.71

10 0.248 54.19 0.515 24.82 11.81 13.00


Percentage change is 26.64 with LSB Parity method for Cover of size 512 X 512




1024 using LSB Parity Method with 10 different message images

embedded in them.

Table No 3.10 Average values of MSE, PSNR, AFCPV, Percentage of bytes changed and AFCPV for 10 messages image in Cover images 16 - 30 of size 1024 X 1024 using LSB Parity Method

Message Average MSE

Average PSNR (db)

Average AFCPV

Average % change



1 0.069 59.81 0.0679 6.86 3.01 3.86

2 0.067 59.92 0.0681 6.68 2.95 3.73

3 0.065 60.03 0.0700 6.48 2.85 3.62

4 0.060 60.40 0.0716 5.96 2.74 3.22

5 0.066 59.96 0.0679 6.60 2.91 3.69

6 0.070 59.78 0.0666 6.97 3.03 3.94

7 0.067 59.91 0.0679 6.69 2.97 3.73

8 0.066 59.96 0.0692 6.59 2.93 3.66

9 0.067 59.89 0.0680 6.72 2.96 3.76

10 0.062 60.21 0.0712 6.19 2.78 3.42

Remark: It is observed that the maximum AFCPV is 0.0716 and maximum Average % change is 6.97 with LSB Parity method for Cover of size 1024 X 1024

Figure 3.26 and Figure 3.27 show the average MSE values for Cover

size 512 X 512 and 1024 X 1024 respectively.


61

Figure 3.28 and Figure 3.29 show the average PSNR values, Figure

3.30 and Figure 3.31 show the average AFCPV values and Figure

3.32 and Figure 3.33 show the average changes i.e. Total bytes

changed, in percent using changes in percent using LSB-3 algorithm

for Cover size 512 X 512 and 1024 X 1024 respectively.


Cover images of (512X512) using LSB-

Parity algorithm for embedding 10

different images of size 128X128


images (1024X1024) using LSB-Parity









LSB-Parity algorithm for embedding 10


0.2630.260

0.254

0.242

0.258

0.266

0.2600.2580.261

0.248

0.2250.2300.2350.2400.2450.2500.2550.2600.2650.270

MSE : LSB Parity Algorithm Cover 512 X 512

MSEC

0.0690.067

0.066

0.060

0.067

0.071

0.0680.066

0.068

0.062

0.0540.0560.0580.0600.0620.0640.0660.0680.0700.072

MSE : LSB Parity Algorithm Cover 1024X 1024


53.96753.996

54.086

54.314

54.031

53.92754.00454.01853.994

54.196

53.700

53.800

53.900

54.000

54.100

54.200

54.300

54.400

PSNRC : LSB Parity Algorithm Cover 512 X 512


59.80159.891

59.976

60.387

59.889

59.693

59.86759.985

59.858

60.183

59.200

59.400

59.600

59.800

60.000

60.200

60.400

60.600

PSNRC : LSB Parity Algorithm Cover 1024X1024



62






images 16-30 of size 1024X1024 using

LSB-Parity algorithm for embedding 10



change in percent. for 15 Cover images

(512 X 512) using LSB-Parity algorithm

for embedding 10 images (128 X 128)


change in percent. for 15 Cover images

(1024X1024) using LSB-Parity algorithm

for embedding 10 images (128 X 128)

Table 3.11, Table 3.13 and Table 3.15 shows the average values of

MSE, PSNR, AFCPV, Percentage of bytes changed, Changes (0 to 1)

and Changes (1 to 0) in percent for Cover images 1 - 15 of size 512

X 512 using LSB-2, LSB-3, LSB Parity Method respectively with 4

different Microsoft Word documents embedded in them.Table 3.12,

Table 3.14 and Table 3.16 shows the average values of MSE, PSNR,

AFCPV, Percentage of bytes changed, Changes (0 to 1) and


0.4650.475

0.493

0.512

0.473

0.452

0.467

0.488

0.472

0.512

0.4200.4300.4400.4500.4600.4700.4800.4900.5000.5100.520

AFCPV : LSB Parity Algorithm Cover 512 X 512


0.0680.068

0.0710.072

0.068

0.0670.068

0.0690.068

0.072

0.0640.0650.0660.0670.0680.0690.0700.0710.0720.073

AFCPV : LSB Parity Algorithm Cover 1024 X 1024


26.28726.033

25.401

24.160

25.791

26.624

25.99625.85026.051

24.756

22.50023.00023.50024.00024.50025.00025.50026.00026.50027.000

% CHANGE : LSB Parity Algorithm Cover 512 X 512


6.8836.714

6.555

5.984

6.706

7.092

6.7506.556

6.770

6.238

5.4005.6005.8006.0006.2006.4006.6006.8007.0007.200

% CHANGE : LSB Parity Algorithm Cover 1024X 1024



63

1024 using LSB-2, LSB-3, LSB Parity Method respectively with 4

different Microsoft Word documents embedded in them.


and AFCPV for 4 Microsoft Word messages in Cover images 1 -15 of size 512 X

512 using LSB-2 Method

Message MSE

PSNR (db)

AFCPV

% change

% change (0- 1)

% change (1- 0)

1 0.07 59.64 0.15 7.07 3.49 3.58

2 0.06 60.56 0.12 5.73 2.86 2.88

3 0.12 57.44 0.26 11.74 5.70 6.05

4

0.10 58.32 0.21 9.58 4.70 4.88


% change is 11.74 with LSB2 method for Cover size 512X512 with Text message




Message MSE

PSNR (db)

AFCPV

% change

% change (0- 1)

% change (1- 0)

1 0.017 65.73 0.02 1.74 0.80 0.95

2 0.014 66.62 0.02 1.42 0.65 0.77

3 0.029 63.50 0.03 2.91 1.34 1.57

4 0.024 64.39 0.03 2.37 1.09 1.28

Remark: It is observed that the maximum value of AFCPV is 0.03 and Average %

change is 2.91 with LSB2 method for Cover size 1024X1024 with Text message




Message MSE PSNR

(db) AFCPV %

change % change (0- 1)

% change (1- 0)

1 0.07 59.56 0.150 7.21 3.40 3.81

2 0.06 60.45 0.117 5.88 2.76 3.11

3 0.12 57.37 0.256 11.92 5.59 6.33

4 0.10 58.24 0.211 9.77 4.58 5.19




64


and AFCPV for 4 Microsoft Word messages in Cover images 16 -30 of size 1024 X 1024 using LSB-3 Method


AFCPV % change

% change (0- 1)

% change (1- 0)

1 0.0184 65.50 0.020 1.84 0.79 1.05

2 0.0151 66.37 0.016 1.51 0.64 0.87

3 0.0301 63.35 0.033 3.01 1.33 1.68

4 0.0248 64.19 0.027 2.48 1.08 1.40

Remark: It is observed that the maximum value of AFCPV is 0.033 and Average


Table No 3.15 Average values of MSE, PSNR, AFCPV, Percentage of bytes changed and AFCPV for 4 Microsoft Word messages in Cover images 1 -15 of size 512 X

512 using LSB-Parity Method


AFCPV % change

% change (0- 1)

% change (1- 0)

1 0.07 59.63 0.15 7.09 3.46 3.63

2 0.06 60.53 0.12 5.77 2.82 2.95

3 0.12 57.43 0.26 11.75 5.65 6.10

4 0.10 58.31 0.21 9.61 4.65 4.96

Remark: It is observed that the maximum AFCPV is 0.26 and Average % change

is 11.75 with LSB Parity method for Cover size 512X512 with Text message

Table No 3.16 Average values of MSE, PSNR, AFCPV, Percentage of bytes changed and AFCPV for 4 Microsoft Word messages in Cover images 16 -30 of size 1024 X

1024 using LSB-Parity Method


AFCPV % change

% change (0- 1)

% change (1- 0)

1 0.0176 65.68 0.020 1.76 0.81 0.96

2 0.0143 66.58 0.016 1.43 0.65 0.78

3 0.0293 63.47 0.032 2.93 1.35 1.58

4 0.0239 64.36 0.027 2.39 1.10 1.29

Remark: It is observed that the maximum value of AFCPV is 0.032 and Average


Figure 3.34 and Figure 3.35 show the average MSE values. Figure



and Figure 3.41 show the average changes i.e. Total bytes changed,

in percent for 4 Microsoft Word messages in Cover size 512 X 512

and 1024 X 1024 respectively using LSB-2 algorithm.


65

Figure 3.34 Average MSE value for 15 Cover images of (512X512) using LSB-2 algorithm for embedding 4 different Microsoft Word documents


Figure 3.36 Average PSNR value for 15 Cover images of (512X512) using LSB-2 algorithm for embedding 4 different Microsoft Word documents


Figure 3.38 Average AFCPV value for 15 Cover images of (512X512) using LSB-2 algorithm for embedding 4 different Microsoft Word documents


0.0710.057

0.117

0.024

0.000

0.020

0.040

0.060

0.080

0.100

0.120

0.140

MSG1 MSG2 MSG3 MSG4


MSEC AVG MSE=0.067

0.0170.014

0.029

0.024

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

MSG1 MSG2 MSG3 MSG4

MSE : LSB 2 Algorithm Cover 1024x1024

MSEC AVG MSE=0.021

59.64460.558

57.435

64.330

52.000

54.000

56.000

58.000

60.000

62.000

64.000

66.000

MSG1 MSG2 MSG3 MSG4

PSNR : LSB 2 Algorithm Cover 512 X 512

PSNRC AVG PSNR=60.492

65.726

66.624

63.503

64.394

61.50062.00062.50063.00063.50064.00064.50065.00065.50066.00066.50067.000

MSG1 MSG2 MSG3 MSG4

PSNR : LSB 2 Algorithm Cover 1024x1024


0.1500.118

0.257

0.020

0.000

0.050

0.100

0.150

0.200

0.250

0.300

MSG1 MSG2 MSG3 MSG4



0.0200.016

0.032

0.027

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

MSG1 MSG2 MSG3 MSG4

AFCPV : LSB 2 Algorithm Cover 1024x1024



66

Figure 3.40 Average values for total change

in percent. for 15 Cover images (512X512) using LSB-2 algorithm for4 different Microsoft Word documents

Figure 3.41 Average values for total change

in percent. for 15 Cover images (1024X1024) using LSB-2 algorithm for 4 different Microsoft Word documents






and 1024 X 1024 respectively using LSB-3 algorithm.



7.075.73

11.74

2.40

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

MSG1 MSG2 MSG3 MSG4



1.7441.421

2.906

2.369

0.000

0.500

1.000

1.500

2.000

2.500

3.000

3.500

MSG1 MSG2 MSG3 MSG4

% CHANGE : LSB 2 Algorithm Cover 1024x1024


0.0720.059

0.119

0.098

0.000

0.020

0.040

0.060

0.080

0.100

0.120

0.140

MSG1 MSG2 MSG3 MSG4


MSEC AVG MSE=0.087

0.0180.015

0.030

0.025

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

MSG1 MSG2 MSG3 MSG4

MSE : LSB 3 Algorithm Cover 1024x1024

MSEC AVG MSE0.022


67





Figure 3.48 Average values for total change in percent. for 15 Cover images (512X512) using LSB-3 algorithm for embedding 4 different Microsoft Word documents

Figure 3.49 Average values for total change in percent. for 15 Cover images (1024X1024) using LSB-3 algorithm for 4 different Microsoft Word documents

59.557

60.451

57.371

58.238

55.50056.00056.50057.00057.50058.00058.50059.00059.50060.00060.50061.000

MSG1 MSG2 MSG3 MSG4

PSNR : LSB 3 Algorithm Cover 512 X 512

PSNRC AVG PSNRC=58.904

65.495

66.370

63.351

64.192

61.50062.00062.50063.00063.50064.00064.50065.00065.50066.00066.50067.000

MSG1 MSG2 MSG3 MSG4

PSNR : LSB 3 Algorithm Cover 1024x1024


0.1500.117

0.256

0.211

0.000

0.050

0.100

0.150

0.200

0.250

0.300

MSG1 MSG2 MSG3 MSG4



0.0200.016

0.033

0.027

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

MSG1 MSG2 MSG3 MSG4

AFCPV : LSB 3 Algorithm Cover 1024x1024


7.2135.878

11.920

9.769

0.000

2.000

4.000

6.000

8.000

10.000

12.000

14.000

MSG1 MSG2 MSG3 MSG4



1.8391.506

3.010

2.482

0.000

0.500

1.000

1.500

2.000

2.500

3.000

3.500

MSG1 MSG2 MSG3 MSG4

% CHANGE : LSB 3 Algorithm Cover 1024x1024



68






and 1024 X 1024 respectively using LSB-Parity algorithm.

Figure 3.50 Average MSE value for 15 Cover

images of (512X512) using LSB-Parity


Microsoft Word documents

Figure 3.51 Average MSE value for 15 Cover

images of (1024X1024) using LSB-Parity



Figure 3.52 Average PSNR value for 15


Parity algorithm for embedding 4 different


Figure 3.53 Average PSNR value for 15




0.070.06

0.12

0.10

0.000

0.020

0.040

0.060

0.080

0.100

0.120

0.140

MSG1 MSG2 MSG3 MSG4

MSE EvPR Algorithm Cover 512 X 512

MSEC AVG MSE=0.086

0.0180.014

0.029

0.024

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

MSG1 MSG2 MSG3 MSG4

MSE : EvPR Algorithm Cover 1024x1024

MSEC AVG MSE=0.021

59.631

60.529

57.433

58.312

55.50056.00056.50057.00057.50058.00058.50059.00059.50060.00060.50061.000

MSG1 MSG2 MSG3 MSG4

PSNR EvPR Algorithm Cover 512 X 512


65.685

66.585

63.475

64.364

61.50062.00062.50063.00063.50064.00064.50065.00065.50066.00066.50067.000

MSG1 MSG2 MSG3 MSG4

PSNR EvPR Algorithm Cover 1024x1024

PSNRC AVG PSNRC=65.027


69

Figure 3.54 Average AFCPV value for 15




Figure 3.55 Average AFCPV value for 15




Figure 3.56 Average values for total change,

change (0-1), change (1-0) all in percent.

for 15 Cover images (512X512) using LSB-

Parity algorithm for4 different Microsoft

Word documents

Figure 3.57 Average values for total change,

change (0-1), change (1-0) all in percent.

for 15 Cover images (1024X1024) using

LSB-Parity algorithm for4 different Microsoft

Word documents

Remark : It is observed that in case of Word documents higher MSE and theryby

lower PSNR is obtained when larger size messages are embedded and viceversa.

The pattern for MSE is same in case of all the three algorithms.

3.4 Discussion

Least Significant bit is one of the simplest techniques. It replaces

the LSB of every pixel directly with the message bit. Such a

0.1520.119

0.258

0.213

0.000

0.050

0.100

0.150

0.200

0.250

0.300

MSG1 MSG2 MSG3 MSG4

AFCPV : EvPR Algorithm Cover 512 X 512


0.0200.016

0.032

0.027

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

MSG1 MSG2 MSG3 MSG4

AFCPV : EvPR Algorithm Cover 1024x1024


7.0925.775

11.751

9.605

0.000

2.000

4.000

6.000

8.000

10.000

12.000

14.000

MSG1 MSG2 MSG3 MSG4

% CHANGE: EvPR Algorithm Cover 512 X 512


1.7621.435

2.925

2.387

0.000

0.500

1.000

1.500

2.000

2.500

3.000

3.500

MSG1 MSG2 MSG3 MSG4

% CHANGE EvPR Algorithm Cover 1024x1024



70

technique can result to easy retrieval of the secret message. In this

chapter, three variations of LSB technique are given. In the first

variation of LSB, called as LSB 2-bit technique, the LSB of every

pixel is adjusted in such a way that XOR operation of LSB and next

to LSB is same as the secret message bit. Similarly the other two

variations are implemented. All these three different variations of

LSB technique are quite robust against easy retrieval of message as

LSB is not directly replaced with the secret message bit.

Experimental results show that LSB 2-bit technique, LSB 3-bit

technique and LSB Parity show lesser values of MSE, RMSE,

percentage of bytes changed and AFCPV for embedding text

message as secret message as compared to message image as

secret message as the total number of bytes for text message are

lesser than the total number of bytes of message image which

means that more amount of text message can be embedded.

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