diffie-hellman.java

// This program calculates the Key for two persons
// using the Diffie-Hellman Key exchange algorithm
class GFG{
	
// Power function to return value of a ^ b mod P
private static long power(long a, long b, long p)
{
	if (b == 1)
		return a;
	else
		return (((long)Math.pow(a, b)) % p);
}

// Driver code
public static void main(String[] args)
{
	long P, G, x, a, y, b, ka, kb;
	
	// Both the persons will be agreed upon the
	// public keys G and P
	
	// A prime number P is taken
	P = 23;
	System.out.println("The value of P:" + P);
	
	// A primitve root for P, G is taken
	G = 9;
	System.out.println("The value of G:" + G);
	
	// Alice will choose the private key a
	// a is the chosen private key
	a = 4;
	System.out.println("The private key a for Alice:" + a);
	
	// Gets the generated key
	x = power(G, a, P);
	
	// Bob will choose the private key b
	// b is the chosen private key
	b = 3;
	System.out.println("The private key b for Bob:" + b);
	
	// Gets the generated key
	y = power(G, b, P);
	
	// Generating the secret key after the exchange
	// of keys
	ka = power(y, a, P); // Secret key for Alice
	kb = power(x, b, P); // Secret key for Bob
	
	System.out.println("Secret key for the Alice is:" + ka);
	System.out.println("Secret key for the Bob is:" + kb);
}
}