Write a Java program to implement the Diffie-Hellman Key Exchange mechanism | Diffie Hellman Key Exchange in Java | Cryptography

AIM: Implement the Diffie-Hellman Key Exchange mechanism using HTML and JavaScript.

HARDWARE AND SOFTWARE REQUIREMENT:

1. Intel based Desktop PC: - RAM of 512 MB

2. Notepad/Notepad ++ editor

3. Net beans / Eclipse

THEORY:

Ø  Diffie Hellman (DH) key exchange algorithm is a way for securely exchanging cryptographic keys over internet(Public channel). Keys are not actually exchanged – they are jointly derived.

Ø  If 1^st Person and 2^nd Person want to communicate with each other, they first agree between them a large prime number P, and a generator (or base) G (where 0 < G < P).

Ø  1^st Person select a secret integer “a” (his private key) and then calculates x=G^a mod P (which is his public key). 2^nd Person chooses his private key “b’, and calculates his public key y=G^b mod P

Ø  1^st Person and 2^nd Person exchange values of x and y.

Ø  1^st Person and 2^nd Person compute symmetric keys by using

K_a=y^a mod P         and             k_b= x^b mod P

Ø  Example:

Step 1 : 1^st Person and 2nd Person get public numbers P = 23,G = 9

Step 2: 1^st Person selected a private key a = 4 and 2^nd Person selected a private key b = 3

Step 3: 1^st Person  and 2^nd Person compute public values

       1^st Person :    x =(9⁴ mod 23) = (6561 mod 23) = 6

 2^nd Person:    y = (9³ mod 23) = (729 mod 23)  = 16

Step 4: 1^st Person  and 2^nd Person exchange public numbers

Step 5: 1^st Person  receives public key y =16 and 2^nd Person receives public key x = 6

Step 6: 1^st Person  and 2^nd Person compute symmetric keys

            1^st Person :  k_a = y^a mod p = 65536 mod 23 = 9

            2^nd Person:    k_b = x^b mod p = 216 mod 23 = 9

                  Step 7: 9 is the shared secret

SOURCE CODE:

import java.util.*;

class DiffieHellman

{

    public static void main(String[] args)

    {

        Scanner sc=new Scanner(System.in);

        System.out.println("Enter modulo(p)");

        int p=sc.nextInt();

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

        int g=sc.nextInt();

        System.out.println("Enter 1st secret number(1st Person)");

        int a=sc.nextInt();

        System.out.println("Enter 2nd secret number(2nd Person)");

        int b=sc.nextInt();

        int A = (int)Math.pow(g,a)%p;

        int B = (int)Math.pow(g,b)%p;

        int S_A = (int)Math.pow(B,a)%p;

        int S_B =(int)Math.pow(A,b)%p;

        if(S_A==S_B)

        {

            System.out.println("1st Person and 2nd Person can communicate with each other!!!");

            System.out.println("They share a secret number = "+S_A);

        }

        else

        {

            System.out.println("1st Person and 2nd Person cannot communicate with each other!!!");

        }

    }

}

  

OUTPUT:

VIVA QUESTIONS:

1.       What is JAVA?

2.       What is Diffie-Hellman Algorithm?

3.       What is java script?

4.       What is Cryptography?

5.       What is Encryption?

6.       What is Decryption?