Can somebody help me with this please. I'm stuck due to my limited knowledge on Matlab.

Below is part of my code for an authentication system using Biometrics. I get the error message below when it comes to gi, the rest works. Please someone enlighten me Error using bitxor Inputs must have the same size.

PWi = input('Enter your password:' , 's');
IDi= input('Enter your identity :' ,'s');
Ki = input('Enter a random number of your choice : ');
Bi = imread('input.bmp');
Bi_double = double(Bi);
BiKi = bitxor(Bi_double,Ki);
fi = SHA(BiKi) % One way hash function on fi
%SHA 256 output -->  fi = 6EEEE0B2284786DD416033159C3AE53E315CAE0FE7A95AB39160ED7CD7E5A685
fi_db = double(fi);
PWi_double = double(PWi)
IDiPWi = strcat(num2str(IDi),num2str(PWi));
IDiPWi_double = double(IDiPWi);

gi = bitxor(IDiPWi_double,fi_db) %this part is not working
% Error using bitxor
% Inputs must have the same size.

ji = bitxor(IDiPWi_double,Ki)

[Gareth Thomas]

if you type:

size(IDiPWi_double) size(fi_db)

You will notice that the sizes do not match and the function needs them to be the same.

Hope this helps.

Answer 1

[Gareth Thomas]

if you type:

size(IDiPWi_double) 
size(fi_db)

You will notice that the sizes do not match and the function needs them to be the same.

Hope this helps.

[Vidya]

Thank you for replying. Yes I did that before and I can't seem to find a solution for that, if there are any to begin with.

I need them both to be of the same size. Is there any way to achieve that?

Answer 2

[Gareth Thomas]

Hi Vidya,

You can do a couple of things:

- force the inputs to be a particular size so that they add up to 256.

- given the strcat command, add characters until you get what you want. this probably plays a role in your algorithm

If you choose for the later, you could calculate how far off the sequence is and add a known letter with:

repmat('A',1,256-size(IDiPWi_double,2))

Or just add a random letter.