Write a program to perform Diffie-Hellman Key Exchange Algorithm.

Post date: Feb 14, 2012 12:24:3 PM

#include <stdio.h>

#include <math.h>

void main()

{

int q,alpha,xa,xb,ya,yb,ka,kb, x,y,z,count,ai[20][20];

printf("Enter a Prime Number \"q\":");

scanf("%d",&q);

printf("Enter a No \"xa\" which is lessthan value of q:");

scanf("%d",&xa);

printf("Enter a No \"xb\" which is lessthan value of q:");

scanf("%d",&xb);

for(x=0;x<q-1;x++) //Primitive Root Calculation

for(y=0;y<q-1;y++)

ai[x][y] = ((int)pow(x+1,y+1))%q;

for(x=0;x<q-1;x++)

{

count = 0;

for(y=0;y<q-2;y++)

{

for(z=y+1;z<q-1;z++)

if(ai[x][y] == ai[x][z])

{

count = 1;

break;

}

if(count == 1)

break;

}

if (count == 0 )

{

alpha = x+1;

break;

}

}

printf("alpha = %d\n",alpha);

ya = ((int)pow(alpha,xa))%q; yb = ((int)pow(alpha,xb))%q;

ka = ((int)pow(yb,xa))%q; kb = ((int)pow(yb,xb))%q;

printf("ya = %d\nyb = %d\nka = %d\nkb = %d\n",ya,yb,ka,kb);

if(ka == kb) printf("The keys exchanged are same");

else printf("The keys exchanged are not same");

}