Title: Colored Image Encryption and Decryption Using Chaotic Lorenz System and DCT2,
Abstract: In this paper, a scheme for the encryption and decryption of colored images
by using the Lorenz system and the discrete cosine transform in two dimensions
(DCT2) is proposed. Although chaos is random, it has deterministic features
that can be used for encryption; further, the same sequences can be produced at
the transmitter and receiver under the same initial conditions. Another
property of DCT2 is that the energy is concentrated in some elements of the
coefficients. These two properties are used to efficiently encrypt and recover
the image at the receiver by using three different keys with three different
predefined number of shifts for each instance of key usage. Simulation results
and statistical analysis show that the scheme high performance in weakening the
correlation between the pixels of the image that resulted from the inverse of
highest energy values of DCT2 that form 99.9 % of the energy as well as those
of the difference image.