International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 03 Issue: 09 | Sep-2016 www.irjet.net p-ISSN: 2395-0072
© 2016, IRJET | Impact Factor value: 4.45 | ISO 9001:2008 Certified Journal | Page 353
Encryption And Decryption Techniques: A Review
Swati Kumari,
M.Tech. Student, Department of Electrical And Electronics, NITTTR Bhopal, M.P., India
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Abstract - Image encryption is the process of hiding the
important data from the unauthorized users. In present time,
the security of multimedia has become necessary. One of the
methods to protect data is encryption. In this paper, different
techniques for the encryption and decryption of digital
colored image has been reviewed.
Key words: Encryption and decryption, cryptography,
symmetric key, asymmetric key.
1. INTRODUCTION
The use of internet has grown rapidly for transmission of
valuable information. The information may be in the form of
multimedia (text, image, video). In our daily life, we share
our valuable images with friends and family. With the rapid
growth in the technology, security is primary need for
multimedia data transmission. The multimedia data is
required to be protected from unauthorized users .To
protect data from unauthorized users data protection
techniques are required. Encryption of data is one of the
important techniques used for data protection.
This paper has been organized as follows-
In section 1, some general guidelines about cryptography has
been provided. In section 2, survey on already existing
research papers has been done. Finally, in section 3, survey
has been concluded.
There are two main types of cryptography:
(i) Symmetric key Cryptography (Secret Key)
(ii) Asymmetric key Cryptography (Public Key)
In symmetric key cryptography, both sender and receiver
use the same key to encrypt and decrypt the data
respectively.
In asymmetric key cryptography, sender and receiver use
different key to encrypt and decrypt the data.
This encryption and decryption technique is used when
secret messages are transmitted from one end to another
end. Usually, very sensitive information has been stored in
computer and transmitted over the internet. Thus, to ensure
the security of data has become key issue. There are number
of algorithms available to encrypt and decrypt image which
is described in next section.
2. LITERATURE SURVEY
2.1 Partial Encryption of Images Using RSA, 2005
M. B. I. Reaz, F. Mohd-Yasin, S. L. Tan, H. Y. Tan [1] have
proposed partial encryption of compressed images. They
have used a secure encryption algorithm to encrypt only the
crucial parts, which are considerably smaller than the
original image. This will result in significant reduction in
processing time and computational requirement for
encryption and decryption. Rivert-Shamir-Adleman (RSA)
algorithm has been used for the encryption. Equation (1)
and (2) has been used to encrypt and decrypt images
respectively.
To encrypt plaintext M,
(1)
To decrypt C,
(2)
Here,
M- 32-bits block which is to be encrypted.
C- 32-bits encrypted block.
(e,n)- 32-bits public key which has been used for encryption.
(d,n)- 32-bits private key which has been used for
decryption.
e, n and d- Modular exponentiation.
RSA encryption algorithm gives PSNR=27.17 and MSE=3.45,
when this algorithm is applied on image dimension of
256*256.
2.2 A highly Adaptive Novel Symmetric Encryption
Using The Sylvester Equation, 2005
Min-sung Koh and Esteban Rodriguez-Marek [2] have
proposed a symmetric encryption technique based on the
Sylvester equation. In this, data has been encrypted by
Hankel matrix that is made up of a symmetric key sequence
and the decrypted information is obtained by solving the
Sylvester equation. There are three theorems that show that
the Sylvester equation is a valid method for encryption. It
generates the huge amount of possible keys that makes the
algorithm an exhaustive search for the best approach
towards breaking the algorithm. Figure 1 shows the block
diagram of encryptor and decryptor. Here, an image matrix