Mapping of Image on S-Box using ECC

Can any one help to Mapping of Image on S-Box using ECC

Answer 1

[Sameer]

Hi Ashuftah

From my understanding, you want to map an image onto an S-Box using “Elliptic Curve Cryptography (ECC)” in MATLAB

You can follow these steps:

1. Image Preparation: First, you need to load your image into MATLAB. If it's a color image, you can convert it to grayscale to simplify the processing. You might also want to resize the image to a manageable size to make the computations easier.

2. Elliptic Curve Definition: Choose the parameters for your elliptic curve. This typically involves selecting coefficients and a prime number that defines the finite field over which your curve is defined.

3. Generating ECC Points: Using the elliptic curve equation, generate points on the curve. This involves solving the curve equation for different values of “(x)” and finding corresponding “(y)” values.

4. Mapping Pixels to ECC Points: You'll need to map the pixel values from your image to coordinates on the elliptic curve. These coordinates can then be used to create an S-Box.

5. Using the S-Box for Encryption: With your S-Box ready, you can proceed to encrypt or decrypt the image. The S-Box essentially acts as a substitution table that transforms pixel values based on the ECC points.

Here's how you can implement:

% Read and preprocess the image
img = imread('input_image.jpg');
grayImg = rgb2gray(img);
resizedImg = imresize(grayImg, [256, 256]); 

% Define the elliptic curve parameters
a = 2; % Example coefficient
b = 3; % Example coefficient
p = 293; % Example prime number for finite field

% Generate ECC Points
points = [];
for x = 0:p-1
    rhs = mod(x^3 + a*x + b, p);
    for y = 0:p-1
        if mod(y^2, p) == rhs
            points = [points; x, y];
        end
    end
end

% Map image pixels to ECC points
% (Assume we have an S-Box function or mapping)
sbox = zeros(1, 256);
for i = 1:256
    sbox(i) = mod(points(i, 1) + points(i, 2), 256); % Simplified mapping
end

% Encrypt/Decrypt using the S-Box
encryptedImg = arrayfun(@(x) sbox(x+1), resizedImg);

% Display the result
imshow(encryptedImg, []);
title('Encrypted Image using ECC-based S-Box');

Hope this helps!