I'm trying to recreate the Diffie-Hellman Key Exchange using addition but i get errors - c

Question

#include<stdio.h>
#include<math.h>
long long int add(long long int a, long long int b,
long long int G)
{
if (b == 1)
return a;
else
return (((long long int)(a + b)) % G);
}
int main()
{
long long int G, x, a, y, b, ka, kb;
G = 43; //the agreed number
printf("The value of G : %lld\n\n", G);
a = 23; //private key for a
printf("The private key a for A : %lld\n", a);
x = add(G, a); //gets the generated key
b = 19; //private key for b
printf("The private key b for B : %lld\n\n", b);
y = add(G, b); // gets the generated key
ka = add(y, a, G); // Secret key for a
kb = add(x, b, G); // Secret key for b
printf("Secret key for the A is : %lld\n", ka);
printf("Secret Key for the B is : %lld\n", kb);
return 0;
}
this is the flow of the code
THIS IS THE EXPECTED OUTPUT/FLOW OF THE PROGRAM but my code has problems i attached an image to show the problem.
A and B will agree upon a number
G = 43 is the agreed number
A will generate a private number a = 23
B will generate a private number b = 19
A will calculate G=43 + a=23 mod G=43 OR 43 + 23 mod 43 = 66 (let's call it x) x = 66
B will calculate G=43 + b=19 mod G=43 OR 43+19mod43 = 62 (let's call it y) y = 62
for A we get x = 66
for B we get y = 62
They will then exchange x and y
x = 66 will go to B
y = 62 will go to A
A will now calculate y + a mod G OR 62+23 mod 43 = 85 (secret number is ka) ka = 85
B will now calculate x + b mod G OR 66+19 mod 43 = 85 (secret number is kb) kb = 85
This is the error that I get

Answer 1

Your 'add' function is declared as taking 3 arguments
long long int add(long long int a, long long int b, long long int G)
but twice you try to call it only passing 2, here
x = add(G, a); //gets the generated key
and here
y = add(G, b); // gets the generated key
reading the logic you posted those should be
x = add(G, a, G); //gets the generated key
and
y = add(G, b, G); // gets the generated key