ANALYSIS OF IMAGE WATERMARKING USING LEAST SIGNIFICANT BIT ALGORITHM

International Journal of Information Sciences and Techniques (IJIST) Vol.2, No.4, July 2012
DOI : 10.5121/ijist.2012.2409 95
ANALYSIS OF IMAGE WATERMARKING USING LEAST
SIGNIFICANT BIT ALGORITHM
Puneet Kr Sharma1
and Rajni2
1
Research Scholar, Deptt. of ECE, SBSCET, Ferozepur
puneet22.1981@rediffmail.com
2
Assistant Professor, Deptt. of ECE, SBSCET, Ferozepur
rajni_c123@yahoo.co.in
ABSTRACT
The rapid advancement of internet has made it easier to send the data/image accurate and faster to the
destination. But thisadvantage is also accompanied with the disadvantage of modifying and misusing the
valuable information through intercepting or hacking.So In order to transfer the data/image to the intended
user at destination without anyalterations or modifications, there are many approaches like Cryptography,
Watermarking and Steganography. This paper presents the general overview of image watermarking and
different security issues. In this paper, Image Watermarking using Least Significant Bit (LSB) algorithm
has been used for embedding the message/logo into the image. This work has been implemented through
MATLAB.
KEYWORDS
Least Significant Bit (LSB), JPEG (Joint Photographic Experts Group), MPEG (Moving Picture Experts
Group), Mean Square Error (MSE) and Peak Signal to Noise Ratio (PSNR)
1. INTRODUCTION
The concept of Image watermarking mainly came into existence in 1990s because of the
widespread of the Internet. At that time an invisible watermark message was inserted into a image
which is to be transfered such that the invisible message will survive intended or unintended
attacks. The first example of a technology similar to digital watermarking is a patent filed in 1954
by Emil Hembrooke for identifying music works. In year 1988, Komatsu and Tominaga was
probably the first to use the term “digital watermarking” [1]. The purpose of digital watermarks is
to provide copyright protection for intellectual property that's in digital format. The
information/logo are embedded in image is called a digital image watermark. The
information/logo where the watermark is to be embedded is called the host image [2, 3].
Digital image watermarking technique provides perceptibility. A watermarking system is of no
importance to anyone if it degeade or distract the cover image to the extent that it being useless,
or highly distracting to its intended user.An ideal watermarked imaged should appear
indistinguishable from the original image even if one uses highest quality equipment. The ideal
watermark must be highly robust so as to be highly resistant to any distortion that can be
introduced during normal use (unintentional attack), or a deliberate effort to remove or alter the
watermark present in the data/image being transferred (intentional attack). Integrity and Security
are also two essential requirements of ideal watermarking [4, 5]. A robust watermark is onewhich
can withstand a wide variety of attacks both incidental (Means modifications applied with a

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purpose other than to hamper the watermark) and malicious (attacks aimed typically to remove or
weaken the watermark) [6].
In the current trends of the world, due to the advancement in technologies, most of the individuals
prefer to use the internet as the primary medium to transfer data from one end to another across
the world. The data transmission is made very simple, fast and accurate using the internet.
However, security threat is the main issue while sending data over the internet. The
private/confidential data can be hacked in many ways. Therefore it becomes mandatory to take
data security into consideration. Data security basically means protection of data from
unauthorized users or hackers and providing high security to prevent data alteration. This area of
data security has gained more attention over the recent period of time due to the massive increase
in data transfer rate over the internet [1, 2]. Information security consists of the measures adopted
to prevent the unauthorized use or change of data or capabilities [3, 4]. Information security is the
protection of information, system and hardware that use, store, and transmits this information.
The data is transmitted from source to destination to the intended user but the hackers might hack
the same data in order to access or manipulate the original data. These types of attacks are
formally known as Security Attacks. In order to circumvent the problem of the security attacks in
data transfers over the internet, many techniques have been developed like: Cryptography,
Stegnography and Digital Image Watermarking.
Digital Image Watermarking is one of the prominent method to fulfill the gap between copyright
issues and digital distribution of data. It is mainly based on Steganographic techniques and
enables useful safety mechanisms. It acts as a very good medium for copyright issues as it
embeds a symbol or a logo in the form of a Watermark, which cannot be altered manually. One
critical factor, which is to be kept in mind while using Watermarking, is to avert any alterations to
the originality of the image after embedding the data. When the image with the secret data is
transmitted over the internet, unauthorized parties may want to hack the data hidden over the
image or change it. If the originality of the image has been altered, then it will be easier to hack
the information by unauthorized persons. In order to improve the security, the Digital Watermarks
are predominantly inserted as transformed digital signal into the source data using key based
embedding algorithm and pseudo noise pattern. The best known Watermarking method that
works in the spatial domain is the Least Significant Bit (LSB), which replaces the least significant
bits of pixels selected to hide the information.
2. Process of Watermarking
The process of watermarking begins when the encoder inserts watermark into image, producing
watermarked image. The decoder extracts and validates the presence of watermarked input or
unmarked input. If the watermark is visible, the decoder is not needed. Otherwise, the decoder
may or may not require a copy of decoder to do this job. If input image and/or watermarked
image are used, the watermarking system is called a private or restricted-key system; otherwise,
the system is public or unrestricted-key system.
The decoder is so designed to process both marked as well as unmarked image. Finally, the
decoder needs to correlate the extracted watermark with original image and compare the result to
a predefined threshold that sets the degree of similarity accepted as a match. If the correlation
matches the threshold value, then watermark is detected i.e. original image belong to the user
otherwise the data does not belong to the user [8, 9].
Digital image watermarking is similar to the concept of watermarking physical objects with the
difference that the watermarking technique is used for digital content instead of physical objects.

97
In digital image watermarking a secret information or logo is embedded in another image in an
impercitible manner. This secret information or logo is called watermark and it contains some
metadata, like security or copyright information about the main data/image. The main image in
which the watermark is embedded is known as cover image since it covers the watermark. The
digital image watermarking system essentially consists of a watermark embedder and a
watermark detector as shown in figure 1.1.
Figure 1.1 Digital Image Watermarking
The watermark embedder inserts a watermark onto the cover image and the watermark detector
detects the presence of watermark information/logo. Sometime a watermark key is also used
during the process of embedding and detecting watermarks. The watermark key has a one-to-one
relation with watermark information. The watermark key is private and known to only intended
users and it ensures that only desirable set of users can detect the watermark. Further, note that
the communication channel can be noisy and hostile (i.e., prone to security attacks) and hence the
digital image watermarking techniques should be resilient to both noise and security attacks [7].
3. Least Significant Bit Modification
The most common method of watermark embedding is to to embed the watermark into the least-
significant-bits of the cover object [6]. Despite being a simple method, LSB substitution suffers
from many drawbacks. Although it can survive transformations like cropping, any addition of
undesirable noise or lossy compression but a more sophesticated attack thatcould simply set the
LSB bits of each pixel to one can fully defeat the Watermark with negligible impact on the cover
object.Once the algorithm is known to a hacker, the embedded watermark could be easily
modified by him without any difficulty.
A more sophesticated approach over conventional LSB method would be to use a pseudo-
random number generator which determine the pixels to be used for embedding watermark based
on a given key[6]. Security of the watermark would be enhanced greatly as the Watermark could
now be no longer is easily viewable to the hackers or any other unintended user. Although this
algorithm is still vulnerable to replacing the LSB’s with a constant value.
4. Results
The result shown below are of the large watermark embedded into a original image using LSB
embedding algorithm, which uses the logo as watermark and spreads it out to full image size.
Results from LSB substitution closely match with the expected one. The watermarked image
shows slight but unnoticeable degradation, while the watermark(logo) was recovered perfectly.
In this method consider the binary value of an image pixel as
00100111 11101001 11001000 00100111 11001000 11101001
11001000 00100111

98
We will hide a binary value for say 10000011 by changing only the LSB of the above mentioned
image pixel value. The result will be as following
00100111 11101000 11001000 00100110 11001000 11101000
11001001 00100111
In this way a watermark is being embedded in the image data by changing only the LSB of the
image data. The Mean Square Error (MSE) and the Peak Signal to Noise Ratio (PSNR) are the
two error measurement methods which are used to compare image compression quality. This ratio
is used as a quality measurement benchmark between the original and a compressed image. The
MSE represents the cumulative squared error between the compressed and the original image,
whereas PSNR represents a measure of the peak error. The lower the value of MSE, the lower
will be the error. To compute the PSNR, the mean-squared error is first calculated using the
following equation:
=
∑ , − ,
,
∗
Where M and N are the number of rows and columns in the input images, respectively and I1
(m, n) is the original image, I2 (m, n) is the Watermarked image. The PSNR is calculated using
the following equation:
= 10 log

Where R represents maximum fluctuation or value in the image, its value is 255 for 8 bit
unsigned number.
TABLE 1. PSNR MSE for Different Bit Subsitution
Method PSNR MSE
LSB or 1st Bit Substitution 55.8784 0.1680
2nd
Bit Substitution 49.7986 0.6811
3rd
4th
5th
6th
7th
MSB or 8th
Bit Substitution 14.3467 2.3900e+003

99
Figure1.Logo to be embedded in image Figure.2.Watermarked Image with LSB
[
Figure.3.Watermarked Image 2nd
bit substitution Figure.4.Watermarked Image 3rd
bit substitution
Figure.5.Watermarked Image 4th
bit substitution Figure.6.Watermarked Image 5th
bit substitution

100
bit substitution Figure.8.Watermarked Image 7th
bit substitution
bit substitution Figure.10. Recovered logo/ Watermark
6. CONCLUSIONS
This paper investigates the classification, attacks and methods of image watermarking and
evaluates LSB based digital watermarking scheme with different bit substitution from LSB to
MSB in image. After we have embedded the secret data in the first bit i.e. LSB in the image we
got Watermarked Image without noticeable distortion on it. However when we embed the data in
the consequent bits i.e. second towards last MSB bit, the image start distorted. The PSNR and
MSE values are calculated and shown in Table1.
REFERENCES
[1] Bender, W., Gruhl, D., Morimoto, N. and Lu, A(1996).: Techniques for data hiding. IBM Systems
Journal, vol. 35, nos. 34.
[2] Saraju Prasad Mohanty(,January 1999 )“Watermarking of Digital Images”, Submitted at Indian
Institute of Science Bangalore, pp. 1.3 – 1.6,.

101
[3] Katzenbeisser, S. and Petitcolas, F(1999).: Information hiding techniques for steganography and
digital watermarking. Artech House Books.
[4] Van Dijk, M. and Willems, F(May 15-16, 2001).: Embedding information in grayscale images. Proc.
22
nd
Symposium on Information and Communication Theory in the Benelux, pp. 147-154, Enschede,
the Netherlands.
[5] A. Nikolaidis, S. Tsekeridou, A. Tefas, V Solachidi(Oct. 2001), “A survey on watermarking
application scenarios and related attacks”, IEEE international Conference on Image Processing, Vol.
3, pp. 991– 993.
[6] Frank Hartung, Martin Kutter(July 1999), “Multimedia Watermarking Techniques”, Proceedings of
The IEEE, Vol. 87, No. 7, pp. 1085 – 1103.
[7] Brigitte Jellinek( Jan 2000), “Invisible Watermarking of Digital Images for Copyright Protection”
submitted at University Salzburg, pp. 9 – 17.
[8] K. Watermarking digital Image and video data. IEEE Signal Processing Magazine, 17:20–46, 2000
[9] C. Rey and J.L. Dugelay(2002). A survey of watermarking algorithms for image authentication.
EURASIP Journal on Applied Signal Processing, 6:613–621.
Authors
Mrs. Rajni is currently Assistant Professor at SBS College of Engineering and Technology, Punjab, India.
She has been pursuing PhD from SLIET, Longowal. She has completed her M.E. from NITTTR,
Chandigarh, India, B.Tech. from NIT, Kurukshetra, India. She has about fourteen years of academic
experience and two years industrial experience. Her areas of interest includes Wireless communication,
Antenna design.
Mr. Puneet Sharma is student at SBS College of Engineering and Technology, Punjab. He has done
M.B.A from G.J.U, Hissar ,Haryana ,B.tech from P.T.U, Jalandhar,India. He has about nine years of
academic experience and two years of industrial experience. His area of interest includes Image
processing. Digital design.

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