Abstract Digital images can be changed easily nowadays through the use of sophisticated software to edit images such as (Adobe Photoshop®). You can look at some manipulated pictures along the lines of the original images without any suspicion that they are also modified. Accordingly, the use of such software to edit the image makes ratification a difficult task and the use of this image in the courts for proving may become impossible.In this paper, a new method has been proposed for water fragile signs depending on the method of Pixel-wise. The proposed method is based on the included secret watermark and check bits in the green layer to the image of the colorful cover with the size of 512x512. The process of including watermark deals with the green class as a chess board with 512 x 512 sizes to avoid the inclusion of sequential bits in the spatial areas of the image of the cover. The process of extracting and discriminating the manipulation of watermark is used to determine whether the manipulation of the image containing watermark was done by an opponent or not. Therefore, the use of the extracted watermark and matrix manipulation to check the image containing watermark sent. Depending on the experimental results, the proposed method provides high quality, low distortion in the images contained watermark PSNR depending on their values. Also, the ability to recognize manipulation in the picture containing watermark in cases such as adding objects to the image containing the watermark, and the application of JPEG compression on image containing watermark, and removing objects from the image containing watermark, repeating the object image containing watermark, and adding a text on image including watermark. Keywords: Check-bits, Fragile watermarking, PSNR, Secret watermark, Watermarked-image.

1. ‫نوروز‬ ‫جامعة‬ ‫جملة‬-‫العدد‬‫الثامن‬-‫الثاني‬ ‫كانون‬610214 - 25Using…./PImage forgery Detection
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Image Forgery Detection Using the Pixel-wise Fragile Image
Watermarking Method in Spatial Domains
Yasir Ahmed Hamza Renas Rajab Asaad
Assistant Lecturer Assistant Lecturer
Faculty of Computer & Information Technology - Nawroz University
‫كورتى‬
‫ث‬ ‫جةندين‬ ‫و‬ ‫فوتوشوب‬ ‫ادوبي‬ َ‫ي‬‫ثروطرام‬ ‫وةك‬ ‫بوينة‬ ‫بةالف‬ ‫بةر‬ ‫زور‬ َ‫ي‬‫َوةك‬‫ي‬‫بش‬ ‫َنا‬‫ي‬‫و‬ ‫لسةر‬ ‫َكرن‬‫ي‬‫كارث‬ ‫و‬ ‫طهورين‬ ‫َن‬‫ي‬‫ثروطرام‬ ,‫دوماهيكان‬ ‫لفان‬‫لسةر‬ َ‫ي‬‫َكرن‬‫ي‬‫كارت‬ ‫َت‬‫ي‬‫جور‬ ‫هندةك‬ ‫هةروةسا‬ .‫دي‬ ‫َن‬‫ي‬‫روطرام‬
‫بةرزةكرن‬ ‫َتة‬‫ي‬‫ده‬ ‫َنةي‬‫ي‬‫و‬ ‫يئ‬ َ‫ين‬‫ثاراست‬ َ‫يف‬‫ما‬ ‫دياركرنا‬ َ‫ي‬‫ذبةرهند‬ .‫كرن‬ ‫هاتية‬ َ‫ي‬‫ل‬ ‫طهورين‬ َ‫ي‬‫جه‬ ‫دياربكةن‬ ‫َن‬‫ي‬‫نةش‬ ‫جاف‬ ‫كرن‬ ‫َنة‬‫ي‬‫ده‬ ‫َنةي‬‫ي‬‫و‬‫هةر‬ ‫دياركرنا‬ ‫بو‬ ‫هاريكارة‬ َ‫ي‬‫ثروطرامةك‬ ‫َتفي‬‫ي‬‫ث‬ ‫جورة‬ ‫ئةف‬ ‫و‬
.‫َنةيدا‬‫ي‬‫دو‬ َ‫ي‬‫طهورينةك‬‫ل‬ ‫كاركرن‬ ‫بو‬ ‫دياركرن‬ ‫هاتية‬ ‫نوي‬ ‫َكةكا‬‫ي‬‫ر‬ ,‫الثةرةيدا‬ َ‫ي‬‫لف‬( ‫َكا‬‫ي‬‫بر‬ ‫َنةي‬‫ي‬‫و‬ ‫َت‬‫ي‬‫َكسل‬‫ي‬‫ث‬ ‫سةر‬watermarking( ‫دطةل‬ ‫يئ‬ ‫َين‬‫ي‬‫نه‬ َ‫ي‬‫َمايةك‬‫ي‬‫ه‬ ‫َكة‬‫ي‬‫ر‬ ‫ئةف‬ .)watermarking‫خو‬ ‫طةل‬ )
( ‫دطةل‬ ‫هةلكريت‬check-bits( ‫ثانيا‬ ‫و‬ ‫َذي‬‫ي‬‫در‬ ‫ب‬ ‫رةطاورةنط‬ َ‫ين‬َ‫ي‬‫لو‬ ‫كةسكدا‬ َ‫ي‬‫رةنط‬ ‫ل‬ )215x215( ‫َسا‬‫ي‬‫بروس‬ ‫دطةل‬ ‫هةلطرتن‬ ‫َما‬‫ي‬‫ه‬ .)watermarking‫ت‬ ‫وةك‬ ‫كةسك‬ َ‫ي‬‫رةنط‬ ‫لسةر‬ )َ‫ي‬‫شرتةجن‬ َ‫ي‬‫ةختةي‬
( ‫ثانيا‬ ‫و‬ ‫َذي‬‫ي‬‫در‬ ‫ب‬215*215( ‫َكا‬‫ي‬‫ر‬ ‫هةروةسا‬ .‫كةفةري‬ ‫ذ‬ ‫َنةي‬‫ي‬‫و‬ ‫ذ‬ ‫ثارجةك‬ ‫ل‬ ‫بةردةوام‬ ‫َت‬‫ي‬‫بت‬ ‫ئاريشا‬ ‫نةبونا‬ ‫ذبو‬ )WEITP‫لسةر‬ َ‫ي‬‫طهورينةك‬ ‫هةر‬ ‫نةبونا‬ ‫يان‬ ‫هةبون‬ ‫كرنا‬ ‫تةكيد‬ ‫بو‬ ‫بكارئينان‬ ‫َتة‬‫ي‬‫ده‬ )
( ‫َكا‬‫ي‬‫ر‬ َ‫ي‬‫هند‬ ‫ذبةر‬ .‫َنةي‬‫ي‬‫و‬watermarking and tampering‫َتة‬‫ي‬‫ده‬ )‫لفي‬ ‫دياركرن‬ ‫هاتينة‬ ‫َت‬‫ي‬‫ئةجنام‬ ‫لديف‬ .‫هنارتن‬ ‫هاتية‬ َ‫ي‬‫َنةي‬‫ي‬‫و‬ ‫ل‬ ‫كرن‬ ‫هاتية‬ َ‫ي‬‫ل‬ ‫طهورين‬ َ‫ي‬‫جه‬ ‫دياركرنا‬ ‫بو‬ ‫بكارئينان‬
( ‫دطةل‬ ‫دبيت‬ ‫َم‬‫ي‬‫ك‬ ‫َنةي‬‫ي‬‫و‬ ‫َت‬‫ي‬‫َكسل‬‫ي‬‫ب‬ ‫بونا‬ ‫ووندا‬ ‫و‬ ‫دبيت‬ ‫زئدة‬ ‫َنةي‬‫ي‬‫و‬ ‫يا‬ ‫َيت‬‫ي‬‫كوال‬ ‫كو‬ ‫دياردبيت‬ ‫الثةرةيدا‬watermarkingَ‫ي‬‫نرخ‬ ‫بكارئينانا‬ ‫لديف‬ )PSNR‫شي‬ ‫هةروةسا‬ .َ‫ي‬‫طهورينةك‬ ‫هةر‬ ‫ديتنا‬ ‫انا‬
‫َدةكرنا‬‫ي‬‫ز‬ ‫ب‬ ‫َنةيدا‬‫ي‬‫دو‬objects( َ‫ي‬‫جور‬ ‫ذ‬ ‫َنةي‬‫ي‬‫و‬ ‫وبكارئينانا‬JPEG compression( ‫َر‬‫ي‬‫لذ‬ )watermarking‫يف‬ ‫َربنا‬‫ي‬‫ذ‬ .)object‫ذ‬(watermarking‫ثاشان‬ ‫وي‬ ‫دووبارةبونا‬ ‫دطةل‬ )
.‫َنةي‬‫ي‬‫و‬ ‫لسةر‬ َ‫ي‬‫تيكستةك‬ ‫نفيسينا‬
‫املستخلص‬
‫مي‬‫الرقمية‬ ‫تغيريالصور‬ ‫كن‬‫حاليا‬( ‫مثل‬ ‫الصور‬ ‫لتحرير‬ ‫متطورة‬ ‫برامج‬ ‫استخدام‬ ‫عرب‬ ‫بسهولة‬Adobe Photoshop®‫ميكن‬ .)‫الصور‬ ‫بعض‬ ‫اىل‬ ‫النظر‬‫الصور‬ ‫غرار‬ ‫على‬ ‫فيها‬ ‫املتالعب‬ ‫الصور‬ ‫بعض‬
‫بأنه‬ ‫اشتباه‬ ‫أي‬ ‫دون‬ ‫األصلية‬‫جرى‬.ُ‫ا‬‫ايض‬ ‫تعديلهم‬‫وعليه‬‫صعبة‬ ‫مهمة‬ ‫عليها‬ ‫املصادقة‬ ‫جيعل‬ ‫الصورة‬ ‫لتحرير‬ ‫الربامج‬ ‫هذه‬ ‫مثل‬ ‫استخدام‬ ‫فان‬‫ل‬ ‫الصورة‬ ‫هذه‬ ‫استخدام‬ ‫يصبح‬ ‫ورمبا‬‫ال‬‫ااحماكم‬ ‫ ي‬ ‫بثبا‬
‫مستحيال‬.‫ ي‬‫البحثية‬ ‫الورقة‬ ‫هذه‬‫مت‬ ،‫طريقة‬ ‫على‬ ‫باالعتماد‬ ‫اهلشة‬ ‫املائية‬ ‫للعالما‬ ‫جديدة‬ ‫طريقة‬ ‫اقرتاح‬Pixel-wise‫وبتا‬ ‫السرية‬ ‫املائية‬ ‫العالمة‬ ‫تضمني‬ ‫على‬ ‫املقرتحة‬ ‫الطريقة‬ ‫هذه‬ ‫وتستند‬ .
‫ا‬ ‫لصورة‬ ‫اخلضراء‬ ‫طبقة‬ ‫ ي‬ ‫التحقق‬‫حجم‬ ‫ذا‬ ‫امللونة‬ ‫لغطاء‬512x512‫احلجم‬ ‫ذا‬ ‫الشطرنج‬ ‫لوحة‬ ‫كانها‬ ‫اخلضراء‬ ‫الطبقة‬ ‫املائية‬ ‫العالمة‬ ‫تضمني‬ ‫عملية‬ ‫تعامل‬ .x512206‫التتابعي‬ ‫التضمني‬ ‫لتجنب‬
‫استخدام‬ ‫يتم‬ .‫الغطاء‬ ‫لصورة‬ ‫املكانية‬ ‫اجملاال‬ ‫ ي‬ ‫للبتا‬‫املائية‬ ‫بالعالمة‬ ‫التالعب‬ ‫ومتييز‬ ‫استخراج‬ ‫عملية‬‫إذ‬ ‫فيما‬ ‫للتاكد‬،‫لذلك‬ .‫ال‬ ‫أم‬ ‫اخلصم‬ ‫قبل‬ ‫من‬ ‫املائية‬ ‫للعالمة‬ ‫املتضمنة‬ ‫الصورة‬ ‫ ي‬ ‫التالعب‬ ‫كان‬ ‫ا‬
‫ل‬ ‫التالعب‬ ‫مصفوفة‬ ‫و‬ ‫املستخرجة‬ ‫املائية‬ ‫العالمة‬ ‫استخدام‬ ‫يتم‬‫ل‬.‫املرسلة‬ ‫املائية‬ ‫للعالمة‬ ‫املتضمنة‬ ‫الصورة‬ ‫من‬ ‫تحقق‬‫و‬‫وتشويه‬ ‫عالية‬ ‫جودة‬ ‫املقرتحة‬ ‫الطريقة‬ ‫تقدم‬ ،‫التجريبية‬ ‫النتائج‬ ‫على‬ ‫اعتمادا‬
‫منخ‬‫قيم‬ ‫على‬ ‫اعتمادا‬ ‫املائية‬ ‫للعالمة‬ ‫املتضمنة‬ ‫الصور‬ ‫ ي‬ ‫فض‬PSNR.‫هلم‬‫املتضمنة‬ ‫الصورة‬ ‫إىل‬ ‫كائنا‬ ‫إضافة‬ ‫مثل‬ ‫حاال‬ ‫ ي‬ ‫املائية‬ ‫للعالمة‬ ‫املتضمنة‬ ‫الصورة‬ ‫ ي‬ ‫بالتالعب‬ ‫التعرف‬ ‫على‬ ‫القدرة‬ ،‫كذلك‬
‫ضغط‬ ‫وتطبيق‬ ، ‫املائية‬ ‫للعالمة‬JPEG‫وإزالة‬ ، ‫املائية‬ ‫للعالمة‬ ‫املتضمنة‬ ‫الصورة‬ ‫على‬‫واضافة‬ ، ‫املائية‬ ‫للعالمة‬ ‫املتضمنة‬ ‫الصورة‬ ‫على‬ ‫الكائن‬ ‫تكرار‬ ،‫املائية‬ ‫للعالمة‬ ‫املتضمنة‬ ‫الصورة‬ ‫من‬ ‫الكائنا‬
‫املائية‬ ‫للعالمة‬ ‫املتضمنة‬ ‫الصورة‬ ‫على‬ ‫النصوص‬.
Abstract
Digital images can be changed easily nowadays through the use of sophisticated software to edit images such as (Adobe
Photoshop®). You can look at some manipulated pictures along the lines of the original images without any suspicion that they
are also modified. Accordingly, the use of such software to edit the image makes ratification a difficult task and the use of this
image in the courts for proving may become impossible.In this paper, a new method has been proposed for water fragile signs
depending on the method of Pixel-wise. The proposed method is based on the included secret watermark and check bits in the
green layer to the image of the colorful cover with the size of 512x512. The process of including watermark deals with the green
class as a chess board with 512 x 512 sizes to avoid the inclusion of sequential bits in the spatial areas of the image of the
cover. The process of extracting and discriminating the manipulation of watermark is used to determine whether the
manipulation of the image containing watermark was done by an opponent or not. Therefore, the use of the extracted
watermark and matrix manipulation to check the image containing watermark sent. Depending on the experimental results, the
proposed method provides high quality, low distortion in the images contained watermark PSNR depending on their values.
Also, the ability to recognize manipulation in the picture containing watermark in cases such as adding objects to the image
containing the watermark, and the application of JPEG compression on image containing watermark, and removing objects
from the image containing watermark, repeating the object image containing watermark, and adding a text on image including
watermark
Keywords: Check-bits, Fragile watermarking, PSNR, Secret watermark, Watermarked-image.
1. Introduction
The digitization of multimedia contents makes them more reliable, with quick and efficient storage,
processing and sending [1]. These features of the multimedia contents may lead to concerns such as
performing illegal copies and redistributing them. The Multimedia contents such as image, sound, text,
and video, can be easily altered and reproduced in a digital domain using nowadays multimedia
editing software [1], [2]. An image can be equivalent to a thousand of words, but it may have tens of
interpretations [2]. For the time being, the images can be altered easily by various sophisticated
image editing softwares such as (Adobe Photoshop®). Also, some of the manipulated images can be
seen similar to the original images without any suspicion that they have been modified. As such, using
such software for image editing makes the authentication of it a challenging mission and the use of
the image for evidencing in the courts of law becomes impossible. Digital image forensics is an area

2. ‫نوروز‬ ‫جامعة‬ ‫جملة‬-‫العدد‬‫الثامن‬-‫الثاني‬ ‫كانون‬610214 - 25Using…./PImage forgery Detection
41
that analyzes images in such scenarios to verify credibility and authenticity through various
techniques. This makes it a popular domain because of its potential applications in many fields, such
as legal documents, news reporting, medical imaging and insurance claim investigations [2]. Digital
images require techniques for dealing with the problems associated with them. Therefore, it is
important to develop methods for protecting the images such as copyright protection, protection
against duplication and owner's authentication [1], [3]. One of these methods is image watermarking.
This technique is a special field of data hiding that can be applied to protect images against those
types of manipulations and duplications. Digital image watermarking is a technique to verify the owner
identification of the image and inhibit the unauthorized copying. This process is done by embedding
the secret data called (Watermark) in the image. The watermark could be a logo of the owner’s or
controlled information embedded in the image contents [1], [3]. The process that embeds the
watermark in the image is called (Embedding Process). The image that is used for embedding the
watermark in it is called (Cover-image). After the embedding process is done, the cover-image is
converted into watermarked-image. Another process used to extract/detect the watermark from the
image called (Extraction/Detection Process). During this process, the extraction/detection process
applied on watermarked-image to extract/detect the watermark. There are some criteria that used to
classify the digital image watermarking techniques such as (robustness, perceptibility and embedding
and extraction/detection methods) [1]. Also, image watermarking techniques can be divided into two
main types. The first type is based on robustness that makes the embedded watermark resist
common image processing operations such as filtering, image compression,….etc. Accordingly, this
type is used for ownership verification [1], [4], [5]. The second type is based on the fragileness called
(Fragile Watermarking) and is used to check authenticity and integrity of digital images [4]-[9]. The
fragile image watermarking techniques are developed with an objective to identify and find any
possible tampered in the watermarked image [3], [4], [7]. In fragile image watermarking, if any
modification is done on the watermarked-image, the watermark removes from it. This means that the
watermarked-image has been tampered. Digital Image verification of its integrity and authentication
are usually fragile in sensing. This means that when watermarked-image is attacked, the embedded
watermark should be entirely or locally removed, according to the type of the attack on the whole or
partial tampering. Therefore, the watermark extraction/detection raises alarms for wrong watermark
[1]. The pure cryptography methods for authentication are usually compared with fragile image
watermarking methods. But, the difference between pure cryptography and fragile image
watermarking is the latter’s capability to find the tampered or damaged areas depending on the
distortion in watermarked-image. Fragile image watermarking methods have some properties [1], [10]:
 Detection of tampering in the watermarked-image.
 The embedded watermark must have perceptual transparency.
 Blind detection without requiring the original image.
 The Detector should be able to find and characterize manipulations made to a watermarked- image.
 The watermarking secret-key spaces should be large.
 The embedding of a watermark by unauthorized parties should be hard.
The fragile image watermarking can be classified into two types: Block-wise fragile watermarking and
Pixel-wise fragile watermarking [4], [7], [8]. In block-wise fragile watermarking, the cover-image is
divided into blocks and watermark information is derived from the necessary content of the block of
the cover-image. In case the watermarked-image is modified, the tampered block and watermark
contained in that block will mismatch. By this inequality, the tampered block can be identified easily
[4], [7], [8]. Block-wise methods identify the tampered block of watermarked-image, but not the
tampered pixels. In Pixel-wise fragile watermarking, the watermark information derived from gray
values of cover-image pixels is embedded into the cover-image pixels themselves. Therefore, the
tampered pixel values of watermarked-image can be identified due to the loss of watermark
information that they carry. In this paper, a new method of pixel-wise based fragile image
watermarking has been proposed. The proposed method is based on embedding the secret
watermark and Check-bits in Green layer of colored cover-image of size 512x512. The watermark
embedding process treats the Green layer as Chess-board of size 512x512 to avoid the sequentially
embedding bits in spatial domains of cover-image. The watermark extraction and identification
tampering process is used for ensuring whether the watermarked image has been tampered by the
adversary or not. As such, extracted watermark and tampering matrix are used for authenticating the
watermarked-image sender’s purposes. Depending on the experimental results, the proposed method
presents a high quality and a low distortion in the watermarked-image according to PSNR values. The
method also helps in identifying the tampering on the watermarked-image in situations such as adding
objects to watermarked-image, applying the JPEG compression on watermarked-image, removing

3. ‫نوروز‬ ‫جامعة‬ ‫جملة‬-‫العدد‬‫الثامن‬-‫الثاني‬ ‫كانون‬610214 - 25Using…./PImage forgery Detection
41
objects from watermarked-image, duplicating the object on the watermarked-image, and adding texts
on the watermarked-image.
2. Literature Review
There are several methods of fragile image watermarking that have been proposed. In [4], the
researchers proposed a method of fragile image watermarking which enabled them to find the
tampered locations in watermarked-image and recover these locations without any error. The
proposed method is the block-wise type. During the embedding process, the cover-image is divided
into 8x8 non-overlapping blocks. For each block, it computes the reference-bits that depend on the
cover-image and check-bits determined by the cover-image content and reference-bits. These two
types of bits as watermarks are embedded into all blocks of the cover-image using a difference
expansion embedding algorithm. The result of the embedding process is a watermarked-image which
then would be sent across the communication channel. On sending the watermarked-image, some of
its content may be modified with some fake information. Accordingly, the watermarks embedded in it
may be removed in the tampered locations of the watermarked-image. Yet the other blocks of the
watermarked-image with their untampered watermarks remain unaffected. During the
extraction/detection process, the check-bits, extracted from each block of watermarked-image and
compared with computed check-bits, are used to identify the tampered blocks. Then, the reference-
bits are extracted from the remaining blocks to recover the original content of the image. Therefore,
the original image can be recovered and restored without any error. Due to tampering, the content
replacement may destroy a part of the embedded watermark as long as the altered area is not too
extensive. A further method of fragile watermarking is proposed in [5]. This method is designed for
recovering the weaknesses of the chaotic watermarking scheme for the authentication of Joint
Photographic Experts Group JPEG images method. So, the proposed method presents a new version
that is capable of resisting attacks, less perceptible and with faster processing. During the embedding
process, the proposed algorithm applied the Discrete Cosine Transform DCT on the cover-image to
embed the watermark in the coefficients of LSB. Also, it used robust chaotic generators to generate
dynamic keys and watermarking information. According to the results of the proposed technique, it is
capable of verifying integrity of the image contents that are sent across the Internet. In [6], the
researchers proposed a block-wise semi-fragile image watermarking method. The proposed
technique uses the logistic map to encipher the features extracted from the original image and then
generate a watermark to embed it in the middle frequency of DCT coefficients of each block of cover-
image. During the extraction/detection process, the features extracted from each block of the
watermarked-image were deciphered. They were then compared with the reconstructed feature
information to generate the tamper array. The tampered block of watermarked-image can be
recovered by using bicubic interpolation. The results of this method are represented by good
imperceptibility for watermarked-image, sensitivity for malicious tampering and capability to identify
and approximately recover tampered areas in watermarked-image. In [7], a pixel-wise fragile image
watermarking was proposed for authentication and tamper localization. During the embedding
process, the secret key was used to scramble the watermark and the integer wavelet transform
applied on cover-image to obtain the four sub-bands (Low-low LL, High-low HL, Low-high and High-
high HH). Then, the watermark was embedded in HH sub-bands coefficients by using odd-even
mapping method. According to the results, the proposed method is good in the detection and
localization of tampered pixels of the watermarked-image. A method of block-wise fragile image
watermarking that depends on k-medoids clustering approach is proposed in [8]. At the embedding
process, the cover-image was divided into 4x4 non-overlapping blocks and for each block, (48) bits
that represent (45) bits of recovery bits and (3) bits for authentication process called (Union bit,
Affiliation bit and Spectrum bit respectively) were calculated. For each block, the authentication bits
are computed by extracting (5) most significant bits MSB of pixel values of the block and the hash
functions applied on them. Also, the recovery (45) bits are calculated by applying the means of
derived clusters and its corresponding mapping bits. Then, by using the secret key, the (48) bits of
each block are mapped pseudo-randomly. At the extraction process, the authentication bits extracted
from watermarked-image and compared with further computed authentication bits were used to
identify the tampering in block. In the case of image recovery, the extracted recovery bits of each
block are used to recover the contents of cover-image. The results of this method show a capability of
identifying and restoring the tampered block effectively with good imperceptibility. A fragile image
watermarking that depends on block-wise for medical image is proposed in [9]. In this method, the
cover-image is divided into three regions called Region of Interest ROI, Region of Non Interest RONI
and border pixels. Then, the Electronic Patient Record and authentication data of ROI computed by
using the hash function message digest MD5 of the medical image are compressed using the Run

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41
Length Encoding and embedded in border pixels. Also, the calculated recovery information is
embedded in the RONI. At the extraction process, the integrity of ROI is verified in order to identify the
tampered blocks inside ROI. So, the original blocks of ROI can be recovered from the RONI by simple
mathematical calculations. According to its results, the proposed method was capable to generate
high-quality watermarked medical image and identify and recover the tampered blocks in the ROI.
3. Proposed Method
The proposed method is divided into three processes, namely watermark generation process,
watermark embedding process and watermark extraction and identification tampering process
WEITP.
3.1.Watermark Generation Process
This process represents the initial step of the proposed method. According to this method, a colored
cover-image of size 512x512 was converted into a grayscale image and then converted into a binary
(Black/White) image. After that, the binary image was resized into half, i.e. the size of the binary
image has become 256x265 which represents the watermark. In order to increase the security of the
watermark, the Blum-Blum-Shub BBS pseudorandom bit generator PRBG is used to create the
pseudorandom bits array PBA. The BBS PRBG is then summarized in the following steps:
 Choose two prime numbers according to the condition:
(1)
 Compute the value of
Choose another positive integer number as and its value must be in range [ , and
. (2)
 Repeat the following step along the size of PBA that equals the size watermark 256x256:
(3)
Where
 The output XOR-ed with the watermark to generate the final secret watermark.
 Fig.1. shows the secret watermark generation process of Lena cover-image.
Fig.1: The secret watermark generation process for Lena cover-image.
3.2.Watermark Embedding Process
This process is used to embed the secret watermark in the cover-image after the first process of
watermark generation. The embedding process works as follows:
 The colored cover-image splits into three layers (Red, Green, and Blue).
 Choose the Green layer for embedding the secret watermark bits and Check-bits.
 The embedding process handles the Green layer as Chess-board of a size equivalent to Green
layer’s size and this means that all white indices are used for embedding all bits of secret
watermark. Each secret watermark bit is embeded in each third LSB of pixel values. While black
indices are used for embedding three Check-bits in each pixel values after converting the pixel
values from decimal into the binary representation and setting the values of the first, second and
third LSBs are set respectively into one. Fig.2. illustrates the Check-bits embedding method.
Watermark
PBA
XOR
Secret
Watermark

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Fig.2: The Check-bits embedding method.
 The Green layer merges with other (Red and Blue) layers to generate the final watermarked image.
Fig.3. shows the watermark embedding process.
3.3.Watermark Extraction and Identification Tampering Process
The watermarked-image sends to the receiver across the communication channel such as the
Internet. During the transferring of the watermarked-image, the adversary may alter it by adding or
removing some objects using image editing software such as (Adobe Photoshop®) supposing that the
adversary is professional in using these kinds of the software. Therefore, the alteration in
watermarked-image cannot be detected by naked-eyes. In this case, the WEITP is required to check
and identify whether the watermarked-image is tampered or not, and determine the tampered any.
WEITP works as follows:
 The watermarked-image is split into three layers (Red, Green, and Blue).
 Choose the Green layer for extracting the secret watermark bits and Check-bits.
 Initialize a new Tampering Matrix TM with zero values which are equal to the size of the Green layer.
The WEITP handles the Green layer as Chess-board, i.e. all white indices are used for extracting all
bits of the secret watermark from the third LSB of each pixel value and put the values sequentially in
another array called extracted secret watermark array ESWA. Black indices are used for extracting
the three Check-bits from each pixel value after converting it from decimal into the binary
representation and taking the first, second and third LSBs respectively. If the (LSB1
st
, LSB2
nd
and
LSB3
rd
) of check-bits of each pixel value do not equal one, this would mean that this pixel has been
tampered. It has also set the tampering matrix value in those pixel value indices to be (255), otherwise
it would be set to (0) according to the equation. Fig.4. illustrates the Check-bits extracting method.
{ (4)
Where,
Fig.4: The check-bits extracting method.
100
Convert into
Binary
0 1 1 0 0 1 0 0
Embed
Check-bits
0 1 1 0 0 1 1 1
Most Significant Bits
MSB
LSB
Pixel Value
103
Pixel Value
After embedding
LSB2LSB3 LSB1
103
Convert into
Binary
0 1 1 0 0 1 1 1
Extract
Check-bits
0 1 1 0 0 1 0 1
Most Significant Bits
MSB
LSB
Pixel Value
255TM (i,j)
LSB3 LSB2 LSB1

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Fig.3: The watermark embedding process.
Apply BBS
PRBG
Read p, q and seed Read Cover-image
Split into Three
Layers (Red,
Green and Blue)
Convert into
Grayscale
Image
Convert into
Binary Image
And resized it
Output
PBA
Apply
XOR
Secret
Watermark
Embed Check-bits in each
Black index of Green layer
Embed all Bits
In White indices
of Green layer
Output
Green layer
Output Watermarked-image
Merge the
Layers (Red,
Green and Blue)

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 Apply BBS PRBG to generate the PBA and XOR-ed with ESWA in order to obtain the watermark.
 Show the watermark and tampering matrix. Fig.5. shows the watermark extraction and
identification tampering process.
Fig.5: The watermark extraction and identification tampering process.
4. Experimental Results
The proposed method has been implemented using the language of technical computing Matlab®
R2009a. So, two programs have been written. The first program is used for embedding the watermark
and Check-bits in the Green layer of the cover-image including the watermark generation process and
generating the watermarked-image. The second program is used for extracting the watermark, finding
the tampering in the watermarked-image and displaying the result in tampering matrix as an image.
Six colored cover-images of the same size 512x512 have been chosen frequently for testing the
performance of data hiding methods. Fig. 6 shows these cover-images after embedding the secret
watermarks and Check-bits as a result of watermarked-images. Also, the reason for selecting the
Green layer for embedding the secret watermark and Check-bits is that the values of peak signal to
noise ratio PSNR of the Green layer, are greater than (Red and Blue) layers PSNR values. PSNR is
the measurement used to compute the quality of the watermarked-image in a metric unit called
decibels. If the value of PSNR is high, this would mean that the quality of watermarked-image is high
and there will be little distortion. Otherwise, if the value of PSNR is low, this would mean a high
distortion in the watermarked-image. In order to compute the PSNR, the mean square error MSE
must be firstly calculated according to the following equation:
MSE= ∑ ∑ (5)
Where, CI is cover-image of size (M x N) and WI is watermarked-image (M x N), 1≤ i ≤ M, 1≤ j ≤ N.
Then the following equation is used to calculate PSNR:
PSNR=10* (6)
If the cover-image is a grayscale image of integer values [0-255], then R=255. Fig.7. illustrates the
PSNR for each (Red, Green, and Blue) layer of watermarked-images.
Apply BBS
PRBG
Read p, q and seed Read Watermarked-image
Split into Three
Layers (Red,
Green and Blue)
Output
PBA
Apply
XOR Extract all Bits
of Secret Watermark
from White indices
Output
Green layer
Tampering
Matrix
Extract all Check-bits
from all Black indices
Watermark

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46.2
46.4
46.6
46.8
47
47.2
47.4
47.6
47.8
48
48.2
48.4
48.6
48.8
49
49.2
Lena Baboon Parrot Peppers Barbara F-16
Red Layer PSNR
Green Layer PSNR
Blue Layer PSNR
Fig.6: A set of watermarked-images (a) Lena,
(b) Baboon, (c) Parrot, (d) Peppers, (e) Barbara, (f) F-16
Fig.7: PSNR for each (Red, Green, and Blue) layer of watermarked-images.
To test the performance of the proposed method against the tampering in the watermarked-image, a
flower has been added to Lena watermarked-image and WEITP has been applied on it. The result of
tampering matrix and extracted watermarked are shown in Fig. 8. Also, the parrot and the text
“Barbara” have been added to Barbara watermarked-image and WEITP has been applied on it. The
results of tampering matrix and extracted watermarked are shown in Fig. 9. According to these
results, the proposed method is capable of identifying the tampering in watermarked-image and the
effect of tampering on the extracted watermark.
(a) (b) (c)
(d) (e) (f)

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Fig. 8: The tampering in Lena watermarked-image (a) Original watermarked-Lena image,
(b) Tampered watermarked-Lena image, (c) Tampering matrix, (c) Extracted watermark
Fig. 9: The tampering in Barbara watermarked-image (a) Original watermarked-Barbara image,
(b) Tampered watermarked-Barbara image, (c) Tampering matrix, (c) Extracted watermark
JPEG compression is a kind of lossy compression that is widely used in image operations [6]. To test
the proposed method against JPEG compression, the Barbara watermarked-image has been
compressed by JPEG compression and WEITP has been applied on the compressed Barbara
watermarked-image. The results are shown in Fig.10. According to these results, the proposed
method presents fragility against this type of compression and the extracted watermark is completely
damaged. The damaging of watermark can serve the adversary in eliminating the authentication for
watermarked-image. In this case, the authentication of watermarked-image will depend on the
tampering matrix that explains the effect of theadversary operation on the watermarked-image.
Fig. 10: The JPEG compression on Barbara watermarked-image (a) Original watermarked-Barbara image,
(b) Compressed watermarked-Barbara image, (c) Tampering matrix, (c) Extracted watermark
Another kind of tampering has been applied on the watermarked-image by adding the F-16 object
from the original F-16 image to the F-16 watermarked-image and WEITP has been applied on the
(a) (b) (c) (d)
(a) (b) (c) (d)
(c) (d)(a) (b)

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(a) (d)(c)(b)
tampered F-16 watermarked-image. The results of tampering matrix and extracted watermarked are
shown in the Fig. 11. In the light of these results, the proposed method is capable of identifying
tampering in such situations.
Fig. 11: The tampering on F-16 watermarked-image (a) Original watermarked- F-16 image,
(b) Tampered watermarked-F-16 image, (c) Tampering matrix, (c) Extracted watermark
In addition to that, another kind of tampering has been applied on the watermarked-image by
transforming watermarked- Baboon image into half. Also, another half part of Peppers image has
been added to it, then WEITP has been applied on the tampered Baboon watermarked-image. The
results of tampering matrix and extracted watermarked are shown in the Fig. 12. According to these
results, the proposed method is capable of identifying tampering in such situations.
Fig. 12: The tampering on Baboon watermarked-image (a) Original watermarked- Baboon image,
(b) Tampered watermarked-Baboon image, (c) Tampering matrix, (c) Extracted watermark
Suppose that the adversary has tampered the watermarked- image by adding texts on it. In this case,
WEITP will be applied on the tampered watermarked- Parrot image to identify the tampering. The
results of this process are shown in the Fig. 13. In the light of these results, the proposed method is
capable of identifying the effect of tampering on the tampering matrix and extracted watermark.
Fig. 13: The tampering on Parrot watermarked-image (a) Original watermarked- Parrot image,
(b) Tampered watermarked-Parrot image, (c) Tampering matrix, (c) Extracted watermark
(a) (b) (c) (d)
(a) (b) (c) (d)

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To compare the proposed method with other methods that have been proposed for fragile image
watermarking according to PSNR values, Table (1) shows PSNR value for each method using Lena
image as a watermarked-image. According to PSNR values, the proposed method presents better
preserving quality for watermarked-image among other methods. In the method that proposed in [7],
the value of PSNR is higher than the value of PSNR for the proposed method. Because this method
used a grayscale Lena image as a watermarked-image. While the proposed method used a color
Lena image as a watermarked-image. In addition, this method applies the embedding process on
watermarked-image using a wavelet transform domain, while the proposed method applies the
embedding process on watermarked-image using a spatial domain.
Table (1) PSNR for each method
Watermarking Scheme PSNR in Decibels (dB)
Method in [8] 40.2 dB
Method in [7] 60.9 dB
Method in [6] 44.2 dB
Method in [4] 29.6 dB
The Proposed Method 48.0 dB
5. Conclusion
In this paper, a new method of pixel-wise based fragile image watermarking has been proposed. The
proposed method is based on embedding the secret watermark and Check-bits in a Green layer of
colored cover-image of size 512x512. The watermark embedding process treats the Green layer as
Chess-board of size 512x512 to avoid the sequentially embedding bits in the spatial domains of
cover-image. According to this method, the white indices are used to embed all the bits of the secret
watermark in the Green layer pixel values, while the black indices are used to embed all the Check-
bits in the Green layer pixel values. The reason behind choosing the Green layer of cover-image for
the embedding process is that the values of PSNR for Green layer are the highest among (Red and
Blue) layers. The WEITP is used for ensuring whether watermarked image has been tampered by
adversary or not. Therefore, extracted watermark and tampering matrix are used for authenticating
the watermarked-image sender’s purposes. Depending on the experimental results, the proposed
method presents a high quality and low distortion in the watermarked-image according to PSNR
values. The method also helps in identifying the tampering on the watermarked-image in situations
such as adding objects to watermarked-image, applying the JPEG compression on watermarked-
image, removing objects from watermarked-image, duplicating the object on the watermarked-image,
and adding texts on the watermarked-image. The proposed method can be used for authenticating
purposes of digital colored images and preventing their forgery. But, the restoration of watermarked-
image to its original watermarked-image after tampering is required in some situations. Therefore,
such a requirement can be addressed for future work.
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