rsa.m

This program applies Message Digest MD5 Algorithm Developed by Maimouna Al-ammar 5th Year, Compu

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% This program applies (RSA) Electronic signature Algorithm         %
% Developed by Maimouna Al-ammar                                    %
% 5th Year, Computer Engineering Department, University of Damascus %
% Information and Network Security Material                         %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%========================================================================
% The RSA algorithm involves three steps: key generation, encryption and
% decryption
%========================================================================

% Remove all variables, functions in the matlab Workspace to forbid any
% conflicts in values
clear;

%========================================================================
% STEP1: KEY GENERATION 
%========================================================================

% 1-choosing two primary numbers p and q
%---------------------------------------
p=randint(1,1,[12 20]);
while (strcmp(isPrimary(p),'false'))
p=randint(1,1,[12 20]);
end 
q=randint(1,1,[23 40]);
while (strcmp(isPrimary(q),'false'))
q=randint(1,1,[23 40]);
end
% 2-computing n=p.q
%-------------------
n=p*q;
% 3-Appplying Ular function on n
%-------------------------------
phi_n=Ular(n);
% phi_n can also be computed as follows: phi_n=(p-1).(q-1)
%--------------------------------------------------------
% 4-Choosing an integer e which satisfies two conditions:
%       I- 1 <e< phi_n   
%      II- gcd(phi_n,e)=1
% Public key is now constituted of {e,n}
%--------------------------------------------------------
e=randint(1,1,[2 40]);
while (strcmp(isPrimary(e),'false'))
e=randint(1,1,[2 40]);
end
while(gcd(phi_n,e)~=1)
e=randint(1,1,[2 40]);
   while (strcmp(isPrimary(e),'false'))
   e=randint(1,1,[2 40]);
   end
end
%----------------------------------------------------------
% 5-Determining an integer e which satisfies next relation:
%      e.d mod phi_n=1   
%      and achieves: 1 <d< phi_n
% Private key is now constituted of {d,n}
%----------------------------------------------------------
maple('e:=',e);
maple('n:=',n);
maple('phi_n:=',phi_n);
d=maple('(e) &^(-1) mod (phi_n)');
d=str2double(d);
maple('d:=',d);
%========================================================================
% STEP2: ENCRYPTION 
%========================================================================
% opening file being encrypted
f1=fopen('Origin.txt','r+');
% Asking for prefered number of blocks which the text will be devided to
blocks=input('number of blocks=');
%===============================================================
% Appending padding so that length of message is multiple of block size
%===============================================================
[Data,count]=fread(f1);
r=mod(count,blocks);
if r==0
fclose(f1);
else
padding=32*ones(1,blocks-r);
cnt=fwrite(f1,padding);
fclose(f1);
end
% Reading file to know new number of bytes
f1=fopen('Origin.txt');
[Data,count]=fread(f1);
fclose(f1);
% Number of bytes in each block
byteperBlock=count/blocks;
% Opening file for ciphering
f1=fopen('Origin.txt');
% Empty array where message data will be stored
M=[];
for i=1:byteperBlock:count
m=fread(f1,byteperBlock);
m=m';
M=[M;m];
end
%--------------------
% Ciphering Operation
%--------------------
% Empty array where ciphered data will be stored
cipheredData=[];
[m1,n1]=size(M);
% First for loop scans all data blocks
% rows loop: each row represents a block of data
 for i=1:m1
    % ciphered block is stored here at every loop
    cipheredBlock=[];
% Second for loop applies ciphering on each block of data
% columns loop
    for j=1:n1 
     maple('M:=',M(i,j));
     cipheredByte=maple('(M) &^(e) mod (n)');
     cipheredByte=str2double(cipheredByte);
     cipheredBlock = [cipheredBlock cipheredByte];
    end
     cipheredData = [cipheredData; cipheredBlock];
 end

cipheredData=cipheredData';
cipheredData=cipheredData(:);
cipheredData=cipheredData';
xlswrite('CipheredData.xlsx',cipheredData);
%disp('Ciphered Data:')
%disp(char(cipheredData))