How can i implement Diffie Hellman Key exchange in Simulink using MATLAB function?

i was trying to do this code in simulink using 2 MATLAB funcions but i keep getting errors.

how can i conver the code into MATLAB function ?

clc;%Clear command window
disp('Diffie Hellman Key Exchange');
disp('-----------------------------------------');
clear 
close all;%Clear variables in workspace and close figure

%Input value of g and p, and ensure that g and p is prime

prime = 0;
while prime == 0
    g = input('Enter a value for g: ');
    p = input('Enter a Value for p: ');
    pg = isprime(g);
    pp = isprime(p);
    if pg == 0
        disp('g is not prime');
    end
    if pp == 0
        disp('p is not prime');
    end
    prime = pg & pp;
end

disp('---Value For X---');
xa = randi([1 p-1]);%Calculate value of Xa
xb = randi([1 p-1]);%Calculate value of Xb

disp(['Xa is: ' num2str(xa)]);%Convert xa to string and display it
disp(['Xb is: ' num2str(xb)]);%Convert xb to string and display it

disp('---Value For Y---');
%Calculate value of Ya and Yb
ya = power(g,xa);
ya = mod(ya,p);
yb = power(g,xb);
yb = mod(yb,p);

disp(['Ya is : ' num2str(ya)]);%Convert ya to string and display it
disp(['Yb is : ' num2str(yb)]);%Convert yb to string and display it

disp('---The Shared Key---');
%Calculate shared key
ha = power(yb,xa);
ha = mod(ha,p);
hb = power(ya,xb);
hb = mod(hb,p);

disp(['Shared Key A: ' num2str(ha)]);%Convert ha to string and display it
disp(['Shared Key B: ' num2str(hb)]);%Convert bb to string and display it

Answer 1

[Harsh Mahalwar]

Hi Elyazeya,

I can understand that you are trying to implement Diffie Hellman key exchange algorithm in MATLAB function block of Simulink.

Upon analysis, I observed that the existing code structure would require some modifications to align with the cryptographic standards and best practices of the Diffie-Hellman algorithm.

Here’s the revised implementation of Diffie Hellman key exchange that might suite your workflow better:

function [Xa, Xb, Ya, Yb] = diffieHellman(p, g, a, b) 
% variables p and g are both publicly available numbers, p is always prime. 
% g is a primitive root of p, both a and b are private values. 
    function pow = powerFunc(a, b, p)  
        if b == 1 
            pow = a; 
        end 
        pow = mod(power(a, b), p); 
    end 
% Xa and Xb are the private keys for Alex and Bob respectively 
    Xa = powerFunc(g, a, p); 
    Xb = powerFunc(g, b, p); 
% Ya and Yb are the final secret keys for Alex and Bob respectively 
    Ya = powerFunc(Xb, a, p); 
    Yb = powerFunc(Xa, b, p); 
end 

(You can add this code to MATLAB function block of Simulink directly.)

You can learn more about Diffie Hellman key exchange algorithm using the following link:

https://www-ee.stanford.edu/~hellman/publications/24.pdf

I hope this helps, thanks!