20320140501014 2

International Journal JOURNAL OF ADVANCED RESEARCH Technology (IJARET),
INTERNATIONAL of Advanced Research in Engineering and IN ENGINEERING
ISSN 0976 – 6480(Print), ISSNAND – 6499(Online) Volume 5, Issue 1, January (2014), © IAEME
0976 TECHNOLOGY (IJARET)
ISSN 0976 - 6480 (Print)
ISSN 0976 - 6499 (Online)
Volume 5, Issue 1, January (2014), pp. 123-137
© IAEME: www.iaeme.com/ijaret.asp
Journal Impact Factor (2013): 5.8376 (Calculated by GISI)
www.jifactor.com

IJARET
©IAEME

HIGHLY SECURED CIPHERED - WATERMARKED
BIOMEDICAL IMAGES
Ali E. Taki El_Deen1, Mohy E. Abo-Elsoud2, Salma M. Saif3
1

2

(IEEE senior member, Alexandria University, Egypt)
(IEEE senior member, Electronics and Communications Dept, Mansoura University, Egypt)
3
(Electronics and Communications Dept, Mansoura University, Egypt)

ABSTRACT
With the rapid development of digital technology, the treatments for digital data such as
copyright protection and ownership demonstration are becoming more and more of greater
importance. This paper presents two forms of data protection; digital watermarking and
cryptography. Digital watermarking is used to enhance medical images security. The proposed
system used is cryptography with watermarking in order to provide high security. In this paper a
digital watermarking using LSB or DWT or DWT-SVD-DCT methods is used and then encrypting
the result using AES encryption algorithm. The experimental results are evaluated with respect to
mean square error, peak signal-to-noise ratio, correlation coefficient, and watermark-to-document
ration. It’s known that the LSB is one of the best ways to achieve the data hiding requirements and
authentication in medical images.
Keywords: AES, Cryptography, Digital Watermarking, DWT, DWT-SVD-DCT, LSB.
1. INTRODUCTION
Multimedia contents are easily spread over the Internet. Due to the ease of delivery and
modification of digital files, the copyrights might be infringed upon. To deal with this problem,
digital rights management (DRM) systems can prevent users from using such contents illegally. In
DRM systems, encryption and robust watermarking are two major schemes for applications [1].

123

International Journal of Advanced Research in Engineering and Technology (IJARET),
ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 1, January (2014), © IAEME

Digital watermarking is a technology that embeds information, in machine-readable form,
within the content of a digital media file. By extracting these secret messages, it can protect the
copyright of and provide authentication to digital media [2].
Cryptography is the science of secret writing with the goal of hiding the meaning of a
message [6].
This paper is organized as follow: Section (2) provides background about watermarking.
Section (3) presents cryptography. Section (4) provides the discussion of the experimental results.
Finally the paper is concluded in Section (5).
2. WATERMARKING
Digital watermarking techniques derive from steganography, which means covered writing
(from the Greek words stegano or “covered” and graphos or “to write”). Steganography is the
science of communicating information while hiding the existence of the communication. The goal of
steganography is to hide an information message inside harmless messages in such a way that it is
not possible even to detect that there is a secret message presents [3].
Some general and very common watermarking requirements [4]:
1.

The watermark should be accessible only to the authorized users. This issue is referred as
security of the watermarking procedure and it is generally achieved by using cryptographic
keys (Security).

2.

The watermark detect ability should be assured regardless of the conventional signal
processing or malicious attacks that may be applied (Robustness).

3.

Generally, although one should provide an irremovable watermark, it should be imperceptible
within the host data (Perceptual transparency).

4.

The watermark should convey a sufficient amount of information.

We are going to work on digital image watermarking in both spatial and transformed domain
and our consideration will be the generation of imperceptible and robust watermark.
Applications of Watermarking [5]:
1. Content labeling and hidden annotations.
2. Broadcast monitoring.
3. Integrity control.
4. Data hiding.
5. Device control.

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Types of watermarking:
According to working domain
Spatial domain
Ex.: LSB, CDMA, Correlation

Transformed domain
Ex.: DCT, DWT

Watermarking

According to type of document

Text

Image

Audio

Video

According to human perception
Fragile

Visible

Semi - fragile

Invisible

Robust

Figure 1: Types of watermarking

3. CRYPTOGRAPHY
Cryptography is the science of keeping secrets secret [7]. The fundamental objective of
cryptography is to enable two people, usually referred to as Alice and Bob, to communicate over an
insecure channel in such a way that an opponent, Oscar, cannot understand what is being said. This
channel could be a telephone line or computer network, for example [8].
Cryptography can be used to provide [9]:
1.
2.
3.
4.
5.

Privacy or confidentiality: keeping information secret from all but those who are authorized
to see it.
Data integrity: ensuring information has not been altered by unauthorized or unknown
means.
Entity authentication or identification: corroboration of the identity of an entity (e.g., a
person, a computer terminal, a credit card, etc.).
Message authentication: corroborating the source of information; also known as data origin
authentication.
Non-repudiation: preventing the denial of previous commitments or actions.
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Types of cryptography:
DES
Symmetric Key
AES
Block ciphers

Blowfish

Stream ciphers

RC4

RC6

A5
Cryptography

RSA
ElGamal
Asymmetric Key
ECC
Diffi-Hellman

Figure 2: Types of cryptography
We are going to encrypt the image using AES encryption algorithm after watermarking it.
We will work on biomedical images but our work can cover many other fields such as space
community, military applications, and mobile systems.
4. WORKING AREA
Cryptography is the most common method of protecting digital content and is one of the best
developed sciences.
However, encryption cannot help the seller monitor how a legitimate customer handles the
content after decryption.
Digital watermarking can protect content even after it is decrypted.
I. Least Significant Bit:
1. Using LSB and 128- bits AES:
LSB method selects a number of pixels from the cover image, and modifies their luminance
to carry watermark bits [10].
The embedding of the watermark is performed choosing a subset of image pixels and
substituting the least significant bit or bits of each of the chosen pixels with watermark bits.
Extraction of the watermark is performed by extracting the least significant bit of each of the
selected image pixels.

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A. Watermarking using LSB:

Figure 3: Original image, original watermark, and watermarked image
B. Encryption and decryption using 128-bits Advanced Encryption Standard (AES):
AES is a symmetric-key block cipher. AES operates on 128-bit data blocks and accepts 128-,
192-, and 256-bit keys. It is an iterative cipher, which means that both encryption and decryption
consist of multiple iterations of the same basic round function. In each round, a different round (or
internal) key is being used. In AES, the number of cipher rounds depends on the size of the key. It is
equal to 10, 12, or 14 for 128-, 192-, or 256-bit keys, respectively [11].
AES encryption round employs consecutively four main operations: Sub Bytes, Shift Rows,
Mix Columns, and Add Round Key. The inverse transformations are called InvSubBytes, InvShift
Rows, InvMix Columns, and InvAddRoundKey. Please note that the last transformation of an
encryption round, Add Round Key, is equivalent to a bitwise XOR and therefore is an inverse of
itself [11].
The whole encryption and decryption block diagrams of AES algorithm are showed in figure
4. The whole operations are presented in figures 5, 6, and 7.
Figure 8 shows the watermarked image, the encrypted – watermarked image, and the
recovered watermarked image.

Figure 4: AES block diagram

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Figure 5: Byte substitution process

Figure 6: ShiftRows and its inverse processes

Figure 7: Mixcolumns operation with its matrix

Figure 8: Watermarked image, encrypted – watermarked image, and recovered watermarked image
128


C. Watermark recovery

Figure 9: Recovered watermarked image and recovered watermark

B. Encryption and decryption using 192-bits AES:

C. Watermark recovery:



129




II. Discrete Wavelet Transform (DWT):
In this technique we will perform watermarking of the input image by decomposing the
image using haar wavelet.
1. Using DWT and 128- bits AES:
A. Watermarking using DWT:



130








131




III. Combined DWT-DCT-SVD Digital Image Watermarking:
SVD is a numerical technique used to diagonalize matrices in numerical analysis. It is an
algorithm developed for a variety of applications. Matrix M is decomposed into three sub matrices
[u, s, v] such that:

;

(1)

Where U and V are the orthogonal matrices such that Ux UT = I and V×VT= I where I is the
identity matrix and S is the diagonal matrix (S1, S2, S3…SN). These values are known as singular
values, and matrices U and V are known as corresponding singular vectors.
1. Using DWT-DCT-SVD and 128- bits AES:
A. Watermarking using DWT-DCT-SVD:


132







133





Fig 33: Recovered watermarked image and recovered watermark
5. MEASURING IMPERCEPTIBILITY
An important way of evaluating watermarking algorithms is to compare the amount of
distortion introduced into a host image by a watermarking algorithm. In our study, the widely used
methods are mean square error, peak signal to noise ratio, correlation coefficients, and watermark to
document ratio.
1. Mean Square Error:

(2)

Where:
• (M, N) are the image dimensions,
• X(i, j) is the pixel value of original (host) image
• X'(i, j) is the pixel value of the watermarked image.
2. Peak Signal-to-Noise Ratio:
PSNR in decibels (dB) is represented as shown:

(3)

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Where:
• MSE is the mean square error between the original image and the watermarked image.
• MAX is the maximum pixel value of the image which is equal to 255 in our implementations
since pixels were represented using 8 bits per sample.
3. Correlation Coefficients:
The correlation factor measures the similarity between the original watermark and the
watermark extracted from the attacked watermarked image (robustness). It take values between 0
(random relationship) to 1 (perfect linear relationship).
The correlation factor is computed as follow:
(4)
Where:
• (N) is number of pixel of the image,
• (Xi) is the pixel value of the original image,
• ( X ) is the average of all pixels value of the original image,
• (Yi) is the pixel value of the modified image,
• ( Y ) is the average of all pixels value of the modified image.
4. Watermark-to-Document Ratio (WDR):
(5
)
Where:
• (M, N) are the image dimensions,
• X(i, j) is the pixel value of the original image,
• X'(i, j) is the pixel value of the watermarked image.

Figure 34: PSNR and WDR

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Figure 35: MSE and Correlation

Table 1: MSE and PSNR of the decrypted watermarked image
WATERMARKING, ENCRYPTION
MSE
PSNR
TYPES
128 BITS AES

3.5986

98.0197

3.5986

98.0197

3.1778

99.2632

192 BITS AES

3.1778

99.2632

256 BITS AES

3.1778

99.2632

128 BITS AES

3.0120

99.7992

192 BITS AES

3.0120

99.7992

256 BITS AES

DWT-DCTSVD

192 BITS AES
128 BITS AES

DWT

98.0197

256 BITS AES

LSB

3.5986

3.0120

99.7992

6. CONCLUSION
In this paper, different watermarking techniques such as LSB, DWT, and DWT-DCT-SVD
have been introduced. Also a brief description of AES encryption algorithm has been presented. This
Paper provides highly secured biomedical images by using the mixture of both watermarking and
encryption. Here we connected the watermarking techniques with 128-bits AES, 192-bits AES, and
256-bits AES encryption algorithms. This provides a more secured algorithm because digital
watermarking can protect content even after it is decrypted. We have also measured the
imperceptibility of the watermarked image and the results showed that DWT-DCT-SVD technique is
better than LSB and DWT techniques.

136


REFERENCES
Books:
[1]
[2]
[3]
[4]

Jeng-Shyang Pan, Hsiang-Cheh Huang, and Lakhmi C. Jain (Eds.), “Information Hiding and
Applications”, ISBN: 978-3-642-02334-7, 2009.
Anthony T.S. Ho Yun Q. Shi H.J. Kim Mauro Barni (Eds.), “Digital Watermarking”, ISBN10: 3-642-03687-2 Springer Berlin Heidelberg NewYork, 2009.
Chun-Shien Lu, “Multimedia Security: Steganography and Digital Watermarking Techniques
for Protection of Intellectual Property”, ISBN: 1-59140-192-5, 2005.
Srdjan Stankovic´, Irena Orovic´, Ervin Sejdic, “Multimedia Signals and Systems”, ISBN:
978-1-4614-4207-3, 2012.

Theses:
[5]

Ahmet BAŞTUĞ, “Watermarking Capacity Improvement by Low Density Parity Check
Codes”, Boğaziçi University, 2002.

Books:
[6]
[7]

Christof Paar, Jan Pelzl, “Understanding Cryptography”, ISBN: 9783642041006, 2010.
Hans Delfs, Helmut Knebl, “Introduction to Cryptography: Principles and Applications”,
Second Edition, ISBN-13: 978-3-540-49243-6 Springer Berlin Heidelberg New York, 2007.
[8] Kenneth H. Rosen, Ph.D., “Cryptography: Theory and Practice”, Third Edition, ISBN-10: 158488-508-4, 2006.
[9] Alfred J. Menezes, Paul C. van Oorschot, Scott A. Vanstone, “Hand Book of Applied
Cryptography”, 4th Edition, ISBN: 9780849385230, 2010.
[10] Feng-HsingWang, Jeng-Shyang Pan, and Lakhmi C. Jain, “Innovations in Digital
Watermarking Techniques”, ISBN: 978-3-642-03186-1, 2009.
[11] C¸ etin Kaya Koc, “Cryptographic Engineering”, ISBN: 978-0-387-71816-3, 2009.

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