InternetCheckSum.m

%Program to generate 16 bit Internet Check Sum
%you can change the length by changing wordSize 
clc
wordSize=16;
Din=input('Input the data string of lenght multiple of 16 bit:');
[m n]=size(Din);

% Making block of data
N=n/wordSize;
copy=zeros(N,wordSize);
for i=0:N-1
    for j=1:wordSize
     copy(i+1,j)=Din(wordSize*i+j);
    end
end
copy;

% Finding Sum
checksum=0;
for k=1:N
    checksum=checksum+bin2dec(num2str(copy(k,:)));
end

%Decimal to binary
d=checksum;
re=zeros(1,N*wordSize);
for i=1:N*wordSize    
    re(i)=mod(d,2);
    d=d-re(i);
    d=d/2; 
end
 re=fliplr(re);

 % Wrap around
 wrap=zeros(N,wordSize);
for i=0:N-1
    for j=1:wordSize
     wrap(i+1,j)=re(wordSize*i+j);
    end
end
wrap;

checksumm=0;
for k=1:N
    checksumm=checksumm+bin2dec(num2str(wrap(k,:)));
end

% Decimal to binary
d=checksumm;
re=zeros(1,wordSize);
for i=1:wordSize
    re(i)=mod(d,2);
    d=d-re(i);
    d=d/2; 
end
 re=fliplr(re);
 
 CheckSumToBeTransmitted=~re
 
 
 
 
 % Example1 --Internet checksum for word Fourozan ASCII(466F726F757A616E)HEX is
 % (7038)HEX
%  Input the data string of lenght multiple of 16 bit:[0 1 0 0 0 1 1 0 0 1 1 0 1 1 1 1 0 1 1 1 0 0 1 0 0 1 1 0 1 1 1 1 0 1 1 1 0 1 0 1 0 1 1 1 1 0 1 0 0 1 1 0 0 0 0 1 0 1 1 0 1 1 1 0]
% 
% CheckSumToBeTransmitted =
% 
%   Columns 1 through 15 
% 
%      0     1     1     1     0     0     0     0     0     0     1     1     1     0     0
% 
%   Column 16 
% 
%      0


% Example2 --Internet checksum for word SNawaz ASCII(534E6177617A)HEX is
 % (E9BF)HEX