data hiding in intermediate significant bit planes

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2012 - International Conference on Emerging Trends in Science, Engineering and Technology

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Data Hiding in Intermediate Significant Bit Planes,

A High Capacity Blind Steganographic Technique

Shabir A. Parah

Post Graduate Department of

Electronics and Instrumentation

Technology, University of Kashmir

Srinagar, India

[email protected]

Javaid A. SheikhPost Graduate Department of

Electronics and Instrumentation Technology, University of Kashmir

Srinagar, India

[email protected]

G.M. Bhat University Science Instrumentation

Center,

University of Kashmir, Srinagar

[email protected]

Abstract — The availability of relatively inexpensive digital

products coupled with the promise of higher bandwidth and

quality of service (QoS) for both wired and wireless

communication networks have made it possible to create,

replicate, transmit, and distribute digital data without any loss in

quality. In such a scenario steganography has received huge

attention from the research community round the globe, as it has

been found useful for information security and under cover

communication. Stegnography refers to covert communication

for transfer of confidential information over a communication

channel. This paper presents a high capacity stegnographic

technique in which secret data is embedded in Intermediate

Significant Bit planes of the cover image. The data to be

embedded is broken down in blocks of relatively decreasing

lengths and each block is embedded in the cover media under

control of a highly secure key. This work shows attractive results

with respect to imperceptibility and capacity when compared

with a few reported techniques in addition to providing adequatedata security.

Keywords- Embedding; Intermediate Significant Bit; Covert-

communication; Steganography.

I. I NTRODUCTION

Stegnography is a type of hidden communication that

literally means “covered writing” [1]. It has been derived from

Greek words stegano means “covert” and graphos means “to

write” The rapid development of technology has increased the

horizon of communication via various wired and wirelessnetworks specially internet. This has resulted in serious

challenges pertaining to integrity and security of data beingcommunicated. Stegnography in such a scenario is being used

to avert adversaries. The goal of steganography is to hide

information inside a harmless cover medium in such a way

that it is not possible even to detect that a secret messageexists in cover medium [2]. Although encryption has been one

of the solutions for information security, but encrypted

messages once intercepted, can easily provide clue to the

adversary or enemy that some message of importance is being

communicated. Steganography, on the other hand, takes

opposite approach and attempts to hide all evidence that

communication is taking place. The issue of critical

importance, in steganography is that, the very presence of a

hidden message in the cover medium must be concealed. Sucha requirement is not critical in watermarking problems.

Security, capacity, imperceptibility and robustness are

essential features of a data hiding system. In this paper we

assume that adversary is passive, as such emphasis has been

given to high hiding capacity coupled with imperceptibility

and security. Rest of the paper is organized as follows. Section

II provides information related application areas of datahiding. Section III provides an insight into data hiding system

features. Section IV differentiates blind and non blind data

hiding systems. In section V literature survey regarding high

capacity data hiding techniques has been presented. Section VI

provides complete description of proposed work. The results

obtained in the proposed technique and the comparison withexisting ones is presented in section VII. The paper concludes

in section VIII.

II. DATA HIDING APPLICATIONS

Data hiding encompasses both digital watermarking and

steganography has been found useful in following areas:

A. Copyright Protection: To protect copyrights and assert

ownership of a Multimedia content. Generally a signature

called watermark is inserted in the medium that is to be

protected against copyright infringments.

B. Content Authentication:The use of fragile water marks is

made for content authentication. Content authentication isused to verify authenticity of a multimedia content and

ensure whether same piece has been received that was

transmitted at transmitter or a changed version of original

piece.




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embedding the payload into the low intensity pixels and hence

maximum utilization of cover image.

Development of spatial domain stegnographic techniques

for gray scale images has been reported in [13]. The schemes

are reported to have high hiding capacity and goodimperceptibility properties. The authors have discussed the

key issues pertaining to data hiding in detail. [14] Reports a

high capacity data embedding scheme based on average

covariance of the Discrete Cosine Coefficients (DCT). The

Most significant Bit (MSB) of the payload is embedded intocover image based on average covariance of cover image. A

Peak Signal to Noise Ratio (PSNR) of 46.31% for hiding

capacity of 12.50% has been reported for test image size

512x512.

An Intermediate Significant Bit (ISB) replacement based

watermarking technique has been reported and presented in[15]. The authors have reported that embedding information in

the intermediate significant bits improves robustnesscompared to data hidden in least significant bits. [16] Reports

a high capacity data hiding technique based on spatial domain.

The host image is partitioned into non-over lapping blocks,with each block containing three 3x3 pixels. In every block

these pixels receive special treatment, with an aim to decrease

the noise and deviations from the original picture values. The

authors have reported PSNR values ranging between 27db to

30db for hiding capacity of 20-26.6%.

Most of the reported techniques emphasize upon highcapacity and are less descriptive about security of payload. In

the proposed technique both the aspects capacity and security

have been given due consideration.

VI. PROPOSED METHODE

The block diagram of proposed high capacity stegnographic

system using ISB data embedding is shown in Fig. 1. Firstly,

Cover image is prepared for data embedding by breaking it

into its constituent bit planes as shown in Fig. 2. The

philosophy behind data embedding in the proposed system is,

more significant the bit plane, lesser the amount of data

embedded in it. This philosophy ensures better perceptualqualities of the stego image. As such data to be embedded in

the bit planes has been divided into three variable length data

vectors of continuously decreasing lengths. The embedding

strategy is depicted in Fig.2. As shown the data vector with

total length is divided into three variable length data vectors,

viz: and of continuously decreasing magnitude.

The data is embedded in the first three ISB planes under the

control of a private key. In order to thwart the adversary data

is not embedded sequentially. The key, which is generated

using Pseudo Random Number Generator (PRNG), ensures a

highly randomized data embedding in the three given bit planes. This process is depicted in Fig. 3. The embedding

process is carried out in data embedder, that outputs an image

containing secret data and is generally termed as stego-image.

The security of data embedded is a function of Key Length.

The used pseudo random number generator (PRNG) is capable

of addressing all the locations in first three Intermediate

Significant Bit planes where data is to be embedded. As such

the PRNG uses 18 bit seed word to generate the key forembedding data.

A. Embedding Strategy and relationship between length

of data vectors : The proposed data hiding system,

breaks the data vector to be embedded, in smaller size

vectors equal, in number to the number of ISB planes in

which data is to be hidden. The lengths of data vectors can

be related in several ways. In the implemened technique

the data has been broken into three blocks with lengths L1,L2 and L3. This is because data is to be embedded in three

ISBs. The relation between the lengths of data blocks is

L1= L/2, L2= 3L/8 and L3=L/8; where L is the total length

of data vector to be embedded in the cover medium. Thedata is embedded in the embedder under the control of a

private key. B. Extraction Strategy: The embedding algorithm uses

private key to embed the data in the ISBs of cover image.

The resultant image yeilded by data embedder is called

stego image. At the receiving end the the extraction

algorithm uses stego-image along with same key as that

used at embedder to extract data from the stego-image.

Since cover image is not needed for the retrieval of secret

data the proposed system falls in the category of blind

detection.

Fig. 1: Proposed high capacity data hiding and corresponding blind

extraction system




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Fig. 2: Data embedding strategy

Fig.3: Data embedding using Random Key

VII. R ESULTS AND A NALYSIS

The requirements of a data hiding system when used for

stegnographic purposes are of twofold viz, high hiding

capacity and imperceptibility. The two parameters

unfortunately are of opposing nature. This is because

embedding more and more data in a cover image results in

deterioration of the cover image quality, and as such an

adversary could easily guess that some data has beenembedded in the cover image. Keeping in view these

conflicting features a reasonable amount of data has been

taken to be embedded in the cover medium so as to keep

degradation in the image quality minimum. For the testing the

efficacy of the proposed scheme a set of nine standard grey

scale test images (512 x512) were used. Table 1 shows all the

used test images with their corresponding stego-image,

besides showing hiding capacity (HC) also termed as payload

and PSNR in decibels in each case. Table 2 presents details of

subset of host test images with amount of percentage dataembedded and corresponding peak signal to noise ratio PSNR.

In all cases the embedding capacity has been fixed as at 25%

that comes out to be (262144x2 bits of payload) except testimage ‘lake’ where the payload of 31.25% has been choosen.

Further a comparison of the proposed data hiding scheme with

that of Zeki et. al [16] can be seen in table 2. Table 3 showsgraphical comparison between the proposed technique and that

of Zeki et. al. The hiding Capacity (HC) and PSNR have been

calculated as follows.

A. Hiding Capacity (HC): The amount of data that can be

embedded in a cover image without deteriorating integrity

of the cover image gives an idea about the hiding

capacity. It is also referred to as payload. Hiding capacity

is represented by bits per pixel (bpp). It is given by (totalnumber message bits/total number of image bits)

multiplied by 100. If n and N respectively denote total

message bits and image bits the hiding capacity is given

by

Hiding Capacity (HC) = (n/N)*100

B. Peak Signal to Noise Ratio (PSNR): It is an important

image, objective, quality index. It is actually a measure of

quality of image when external data is embedded in it. It

gives an idea about how much deterioration has

embedding caused to the image. It is represented as

Where ‘mse’ is mean square error and is given by

Where N and M are image dimensions, and represent

original and stego images respectively.

TABLE I. VARIOUS TEST IMAGES AND THEIR STEGO VERSIONS

Details of host image, its stego version, PSNR and percentage

of data embedded

Host Image Stego Image

Boats Boats, HC=25%,

PSNR=37.50db

Peppers Peppers, HC=25%,PSNR=37.65 db




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Airplane Airplane, HC=25%PSNR=37.63 db

Lake Lake, HC=31.25%

PSNR=36.08 db

Barbara Barbara, HC=25%PSNR=37.59 db

Milk drop Milk drop, HC=25%PSNR=37.48 db

CameramanCameraman, HC=25%,PSNR=37.97 db

Baboon Baboon, HC=25%,

PSNR=37.64 db

Lena Lena, HC=25%,PSNR=37.55 db

TABLE II. CAPACITY VERSUS PSNR OF VARIOUS TEST IMAGES OF

PROPOSED ALGORITHM

TABLE III. COMPARISON BETWEEN PROPOSED AND ZEKI [16] TECHNIQUE




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VIII. CONCLUSION

A secure and high capacity data hiding technique with blind

detection is presented in this paper. The image in which the

data is embedded has been broken into its constituent bit

planes. The data to be embedded in the cover medium has been divided into three variable length data vectors. The datavectors are subsequently embedded in first three ISB planes

using a private key generated by Pseudo Random Number

Generator (PNRG). The PRNG not only embeds data pseudo

randomly in various bit planes but it also ensures

pseudorandom embedding of data at various pixel locations,

thus providing an adequate security to the data carried by the

cover image. The technique has been implemented using

MATLAB 7. The proposed technique, on an average provides

about 8db improvement in PSNR when compared with [16]

even when payload is increased on an average by 2.2%. The

results clearly show that the proposed technique has a better

performance.

R EFERENCES

[1] C. Cachin, “An information-theoretic model for steganography,”Information and Computation, Vol. 192, 41-56. 2004

[2] N. Provos and P. Honeyman, “Hide and Seek : an introductionto steganography”, Computer journal of IEEE security and privacy magazine, Vol. 2(3), pp. 32-40, 2003.

[3] M.D. Swanson, M. Kobayashi, and A.H. Tewfik, “Multimediadata-embedding and watermarking technologies,” Proc. IEEE,vol. 86, pp. 1064-1087, June 1998.

[4] G. M Bhat, Shabir A. Parah et.al, “VHDL Modeling andSimulation of Data Scrambler and Descrambler for Secure DataCommunication”, Indian Journal of Science and Technology,Vol 2, No. 10, pp. 41-43, 2009.

[5] G. M Bhat, Shabir A. Parah et.al, “FPGA Implementation of Novel Complex PN Code Generator based data Scrambler and

Descrambler”, Maejo Int. J. Sci. Technolgy. 4(01), 125-135,2010.

[6] Shabir A. Parah et.al, “On the realization of a secure, highcapacity data embedding technique using joint top-down anddown- top embedding approach” Elixir Comp. Sci. & Engg. (49)10141-10146 , 2012

[7] P. Wah Wong and E. J. Delp, editors. “Security andWatermarking of Multimedia Contents II,”. Society of Photo-optical Instrumentation Engineers, volume 3971, 2000.

[8] R.G. Schyndel, A. Tirkel, and C. Osborne, “A digitalwatermark,” in Proc.IEEE Int. Conf. Image Processing (ICIP), pp. 86-90, 1994.

[9] R.B. Wolfgang and E.J. Delp, “A watermark for digital images,”in IEEEProc. Int. Conf. Image Processing, Lausanne,Switzerland, Sept. vol. 3, pp. 219-222. 1996.

[10] W. Bender, D. Gruhl, and N. Morimoto, “Techniques for datahiding,” IBM Syst. J., vol. 35, nos. 3-4, pp. 313-336, 1996.

[11] A. Masoud and I. Subariah “Adaptive Steganography schemeusing More Surrounding pixels,” International Conference onComputer Design and Applications, 225-229. 2010.

[12] Mehdi Hussain and Mureed Hussain, “Pixel Intensity Based

High Capacity Data Embedding Method,” InternationalConference on Information and Emerging Technologies,1 – 5,2010.

[13] N. I. Wu and M. S. Hwang, “Data Hiding: Current Status andKey Issues,” International Journal of Network Security, 4(1), pp.1-9. 2010.

[14] N. Sathisha et. al, “Embedding Information In DCT CoefficientsBased On Average Covariance” International Journal ofEngineering Science and Technology (IJEST), 3 (4), 3184-3194.2011.

[15] M. A Zeki and A. A. Manaf, “A Novel Digital WatermarkingTechnique Based on ISB (Intermediate Significant Bit)” , Worldacademy of science Engineering and Technology, vol. 50,989-996, 2009

[16] M. A. Zeki et. al, “High watermarking capacity based on spatial

domain technique” Information technology journal:, 10(7),1367-1373, 2011.

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