How can i implement galois counter mode (GCM) in matlab?

The image above shows an algorithm to find the multiplication of 2 blocks using galois field.I tried implementing it,but got an error.Can somebody help me??

clc;
clear all;
close all;
x=01101101;
Z=00000000;
v=11001011;
for i=0:1:8
    if x(i)== 0
        Z(i+1)= Zi;
    else xi == 1
        Z(i+1)= xor(Zi,Vi);
    end
end

The error was: Subscript indices must either be real positive integers or logicals.

Error in algo1 (line 8) if x(i)== 0

Answer 1

[Ahmed Grera]

Hi Darsana P M

You can retype it like this:

clc;
clear all;
close all;
x=[0 1 1 0 1 1 0 1];
Z=[0 0 0 0 0 0 0 0];
v=[1 1 0 0 1 0 1 1];
for i=1:1:8  %-----or use i=1:8------
    if x(i)== 0
        Z(i+1)= Z(i);
    else x(i) == 1;
        Z(i+1)= xor(Z(i),v(i));
    end
end
Z

Greetings Eng. Ahmed G

Good luck

[Ahmed Grera]

The site does not accept zero We always start with one number like:

for i=1:N %------N any number------

[Darsana P M]

Thanks a lot sir for the correction. It was really helpful. But I have a doubt, the final answer of Z is it for i=8. How can i get the answer for each i??

And also,one more doubt, if the number of bits is extended from 8 bits to 128 bits,what should i do?

[Ahmed Grera]

Hi Darsana P M

Following the answer I have just posted to your question.

Would you please be so kind to have a look and if it helps, would you please consider marking my answer as accepted answer by clicking on the Accepted Answer? thanks in advance, awaiting

[Zeeshan Abbas]

Is it showing (nonce+counter) XOR (key)??

let say: x=nonce

v=key

z = output?

Am i right?