An Effective Color Image Encryption Based on Henon Map, Tent Chaotic Map, and Orthogonal Matrices

. 2022 Jun 8;22(12):4359. doi: 10.3390/s22124359

Algorithm 5. Pixel Decryption Process

Input: Cipher image

C

, Secret keys

K_{1}, K_{2}, K_{3}

, Henon Map (1), CTM (3).
Output: Colored image

I

1.
$Place the matrix C^{'}$ $of the cipher image in an array of order M = P \times Q \times 3$ .
2.
$Generate a sequence W$ $of an order M = P \times Q \times 3$ $by using key K_{3}$ and XOR it with the integer sequence generated from the relation (4).
3.
$Each element of C^{'}$ is pre-decrypted as:
$E_{j} = C_{j} \oplus P_{j} \oplus E_{j - 1} j = 1, 2, 3, …, M$
4.
$Generate an orthogonal matrix K_{2}$ as in Algorithm 2.
5.
$Transform the one - dimensional array E$ $in block vectors L_{r}$ $of size 3 \times 1$ .
6.
Hill cipher is executed by using the formula
$A_{r} = K_{2} \times L_{r} (m o d 256)$
7.
$Change all A_{r}^{'} s$ $in one dimensional array L$ .
8.
$Use the \sec ret key K_{1}$ $, iterate the Henon map (1) to generate a sequence H$ $and obtain \underline{H}$ $by cataloguing H$ in ascending order.
9.
$Obtain the permutation array by inverse transformation position J^{- 1}$ .
10.
$Using J^{- 1}$ $on L$ $to obtain Y$
11.
$Rewrite Y$ $in a matrix formation of order M$ $to get image I$