pub_key_gen.m

elgamal elgrithm by matlab

%
% The public key generator for the receiver
%
% Here the receiver chooses p, Alpha, and is assigned the
% secret key (the secret key is already set in this algorithm.

% The public key Betaa is computed.

% Allow these variables to be global throughout the session
global y1 y2 num_plaintext 

% Load numtheory for Maple which has useful funcions
maple('with(numtheory)');

disp('Warning: it may take a few minutes to generate Alpha in some cases.')

% **********Set the secret key for the user*********** %
% This is where you need to change the code to change the secret key
maple('a:=', 245674);

disp(' ')
disp('Publishing p, Alpha and Betaa:')

% Generate a random prime p (p is between 0 and 2^128)
maple('p:=','nextprime(rand(0..2^128)())')
p = maple('p');

% Compute the primitive root Alpha
maple('Alpha:=','primroot(p)')
Alpha = maple('Alpha');

% Compute the public key Beta
maple('Betaa:=','(Alpha^a) mod p')
Betaa = maple('Betaa');