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Image Encryption Using Lagrange-Least Squares Interpolation
Authors: Mohammed A. Shreef , Haider K. Hoomod
Number of views: 595
Today, information security is becoming one of the most important issues in social network era. The fast
development of network technology leads to facilitate many aspects of life, but it also gives attackers or
unauthorized users an opportunity to violate the privacy of people. Encryption is a common technique that
exists to protect information security, thereby deters attackers. Actually, digital images are widely used in
storage and communication applications. Therefore, the protection of image data from unauthorized access
has attracted much attention recently. This paper adopts a new image cryptosystem, XLLS, which consists
of two main parts: encryption/decryption algorithm and ciphered key. The encryption algorithm is composed
of two main stages: the diffusion stage and the substitution stage. In the diffusion stage, the pixels values
are modified so that a slight change in one pixel is spread out to all pixels in the image. This stage
completely depends in its construction on ‘XOR’ operation. For the substitution stage, it mainly composes
of two encryption processes: Lagrange Process (LP) and Least Squares Process (LSP). This stage aims at
changing the value of each pixel in the diffused image by using the principles of Lagrange interpolation and
least squares method. For the decryption algorithm, it is simply the reverse of the encryption algorithm. On
the other hand, the proposed cryptosystem introduces two different approaches of initial key. The users
have option to choose any one of them to encrypt the plain-image. In the first approach, the proposed
cryptosystem uses a key whose length is of 192 bits (24 bytes) in hexadecimal system as its input, and
then expands it by using AES-192 key expansion algorithm. Conversely, in the second approach, the
proposed cryptosystem uses an image as a key to cipher the plain-image, and then processes and
expands the key-image by using the CBI key expansion algorithm.