Asymmetric double-image encryption using twin decomposition in fractional Hartley domain
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Date
2022
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Abstract
Twin decomposition, consisting of equal and random modulus decompositions, not only makes
a cryptosystem asymmetric but also resists special attack. A new double-image asymmetric crypto
system using twin decomposition in fractional Hartley domain is proposed. An input grayscale
image, bonded with another grayscale image as its phase mask, is transformed via fractional Hartley
transform. Equal modulus decomposition is applied on the resulting image, giving us two inter
mediate images. One of them is subjected to another fractional Hartley transform followed by ran
dom modulus decomposition, whereas the other serves as the first private key. The application of
random modulus decomposition also results in two images: encrypted image and the second private
key. During the process of decryption, firstly the encrypted image is combined with second private
key and thereafter it is subjected to inverse fractional Hartley transform. The resulting image is
then combined with the first private key, and followed by another inverse fractional Hartley trans
form, thus recovering the two original images. The proposed cryptosystem is validated for pairs
of grayscale images.