An Adaptive LSB-OPAP based Secret Data Hiding

by

TEJAS.S

under the guidance of

Prof. PADMAJA VIJAYKUMAR

ECE Dept. AIeMS

Introduction

Ways of sending information

encryption steganograhy

Steganography !

encrypt msg cover file

watermarking

Advantages

secrecy

Imperceptibility

High capacity

Accurate extraction

files such as audio,video,image,etc..

Image Steganography process

Classical Methods

Kirchoff’s golden rule

Adaptive Steganography

4LSB substitution technique

Model authentication technique

Objective of proposed method

Enhance embedding capacity of image .

An adaptive number of least significant bits substitution method with private stego-key.

verify whether the attacker has tried to modify the secret hidden information in the stego-image.

embed the hidden information in the cover image and use digital signature using a key to verify the integrity from the stego-image.

Methodkey1 consists of some gray-level ranges.Each range substitute different fixed number

of bits into LS part of the 8-bit gray value of the pixels.

Pixel gray value “g” that fall within the range Ai-Bi is changed by embedding message bits of secret information into new gray value “g’ ”.

OPAP is used that make the new gray value “g’ ” fall within the range Ai-Bi.

Digital signature of the secret information with the key2 were obtained and appended with the information

Private stego-key generation For a gray scale image 8-bit is used

to represent intensity of pixel, so there are only 256 different gray values any pixel may hold.

Different pixels in image may hold different gray values

let four ranges of gray levels are < A1-B1, A2-B2, A3-B3, A4-B4 > each range starting and ending value are in 8-bits.

Method to decide Bits insertion in each range

Let the four gray ranges decided by the stego-key are <A1-B1, A2-B2, A3-B3, A4-B4>

number of pixel count from cover image in each range are < N1, N2, N3, N4 >.

Let the ranges be 0-64, 65-127, 128-191, 192-255

Let ranges hold no of pixels 34, 13238, 17116, 35148.

LSB substitution

OPAP – Optimum Pixel Adjustment Process

K = K+1

Example :consider a gray level range 0-32, 3 – bits substitution are 111

1 : let 00100000 (32) be pixel value of g,2 : after LSB method, g’ = 001000111 (39)3 : g’ < 32, K+1 bit of g’ changed from 0

to 1 or via- versa (00101111) and checked again to fall within range if not K+2 bit is changed (00111111) and so on until gray value fall within range 00011111(31).

IMPLEMENTATION OF ALOS

ENCODING ALGORITHM

Input: Cover-image, secret message, keys K1, K2. Output: Stego-image.

Step1: Read key K1 based on gray-Level ranges. Step2: Read cover image Step3: Decide No. of bits insertion into each range described in

section 2.3 Step4: Read the secret message and Convert it into bit stream form. Step5: Read the key K2. Step6: Find the signature using K2 and append with the message

bits. Step7: For each Pixel 7.1: Find gray value g. 7.2: Decide the K-bits insertion based on gray ranges. 7.3: Find K-message bits and insert using method given in section 2.4 7.4: Decide and adjust new gray Value g’ using method described in

Optimum pixel adjustment process. 7.5: Go to step 7. Step 8: end

EXTRACTION ALORITHM

Input: Stego-image, keys K1, K2; Output: Secret information;

Step1: Read key K1 based on gray-level ranges. Step2: Read the stego image. Step3: Decide No. of bits extraction into each range

described in section 2.3. Step4: For each pixel, extract the K-bits and save into file. Step5: Read the key K2 and find the signature of bit

stream Step6: Match the signature. Step7: End

Advantages : High hiding capacity compared to LSB Substitution

technique. Robust in nature, i.e., highly secure algorithm since

two keys (key-1 and key-2) are used. We get good quality of the stego image. High water marking level. Provides maximum possible payload. Embedded data is imperceptible to the observer.

Limitations : High computational complexity. Requires a lot of overhead to hide a relatively

bits of information.

This can be overcome by using HIGH SPEED COMPUTERS.

ApplicationsIn secret communication system.Military applications.Hiding and protecting of secret

data in industry.Navy and Air force.Business Deals

Results and Discussions Lena and baboon 256 × 256 × 3 colour digital images

Range Cover image

Max bits that can be

embedded (payload)

No of bits embedded

Capacity(bits/pixel)

PSNR

Range1

Lena 653149

51360 3.8016 44.9412

4768 3.141 55.5705

115360 3.2268 40.8688

Baboon 609524

51360 3.2927 44.7668

4768 3.2 54.8287

115360 3.0352 41.7503

Range2

Lena 693700

51360 3.624 43.494

4768 3.7338 53.4812

115360 3.6078 40.3313

Baboon 700087

51360 3.6488 43.2479

4768 3.7192 53.6941

115360 3.5019 40.2084

The input cover image

0

200

400

600

The histogram of input cover image

0 100 200

The output stego image

0

200

400

600

800

The histogram of stego image

0 100 200

Experimental result using Range1 for Baboon cover image

The input cover image

0

200

400

600

800

The histogram of input cover image

0 100 200

The output stego image

0

500

1000The histogram of stego image

0 100 200

Experimental result using Range2 for Lena cover image

Conclusion Enhanced embedding capacity of image .

An adaptive number of least significant bits substitution method with private stego-key.

whether the attacker has tried to modify the secret hidden information in the stego-image.

embeded the hidden information in the cover image and use digital signature using a key to verify the integrity from the stego-image.

Experimental results verify that the proposed model is effective and efficient.

References S. Dumitrescu, W. X. Wu and N. Memon, “On steganalysis of

random LSB embedding in continuous-tone images”, Proceeding of International conference on image Processing, Rochester, NY, pp. 641-644, 2002.

A. Cheddad, J. Condell, K. Curran and P. McKevitt, “Enhancing Steganography in digital images”, IEEE - 2008 Canadian conference on computer and Robot vision, pp. 326-332,2008.

Ko-Chin Chang, Chien-Ping Chang, Ping S. Huang, and Te-ming Tu, “A novel image steganographic method using Tri-way pixel value Differencing”, Journal of multimedia, vol. 3, issue 2, June 2008.

K. S. Babu, K. B. Raja, K. Kiran Kumar, T. H. Manjula Devi, K. R. Venugopal, L. M.Pataki, “Authentication of secret information in image steganography”, IEEE Region 10 Conference, TENCON-2008, pp. 1-6, Nov. 2008.

S. K. Moon and R.S. Kawitkar, “Data Security using Data Hiding”, IEEE International conference on computational intelligence and multimedia applications, vol. 4, pp. 247251, Dec 2007

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