Java program to implement Diffie Hellman Algorithm (CSS)

import java.io.*;

import java.math.BigInteger;

public class Deffie{

public static void main(String[]args)throws IOException

{

BufferedReader br=new BufferedReader(new InputStreamReader(System.in));

System.out.println("Enter prime number:");

BigInteger p=new BigInteger(br.readLine());

System.out.print("Enter primitive root of "+p+":");

BigInteger g=new BigInteger(br.readLine());

System.out.println("Enter value for Alice private kay less than "+p+":");

BigInteger x=new BigInteger(br.readLine());

BigInteger R1=g.modPow(x,p);

System.out.println("R1="+R1);

System.out.print("Enter value for Bob private key less than "+p+":");

BigInteger y=new BigInteger(br.readLine());

BigInteger R2=g.modPow(y,p);

System.out.println("R2="+R2);

BigInteger k1=R2.modPow(x,p);

System.out.println("Key calculated at Alice's side:"+k1);

BigInteger k2=R1.modPow(y,p);

System.out.println("Key calculated at Bob's side:"+k2);

System.out.println("deffie hellman secret key Encryption has Taken");

}

}

Output:

codept@codept-04 ~/Desktop/chan $ java Deffie

Enter prime number:

23

Enter primitive root of 23:5

Enter value for Alice private kay less than 23:

4

R1=4

Enter value for Bob private key less than 23:7

R2=17

Key calculated at Alice's side:8

Key calculated at Bob's side:8

deffie hellman secret key Encryption has Taken