Add Diffie Hellman Key Exchange

ICS/Assignment3/AliceDH.java

@@ -0,0 +1,36 @@
+import java.io.*;
+import java.math.BigInteger;
+import java.net.ServerSocket;
+import java.net.Socket;
+import java.util.Scanner;
+
+public class AliceDH
+{
+	public static void main(String[] args) throws IOException
+	{
+		ServerSocket server = new ServerSocket(8088);
+		System.out.println("Waiting for connection on port " + server.getLocalPort());
+		Socket soc = server.accept();
+		System.out.println("Accepted connection from " + soc.getRemoteSocketAddress());
+		DataInputStream dis = new DataInputStream(soc.getInputStream());
+		DataOutputStream dos = new DataOutputStream(soc.getOutputStream());
+
+		int P = dis.readInt();
+		int G = dis.readInt();
+		int y = dis.readInt();
+		System.out.println("P = " + P + " \nG = " + G + "\nBob's Public key(y) = " + y);
+
+		Scanner sc = new Scanner(System.in);
+		System.out.print("Enter Private key : ");
+		int a = sc.nextInt();
+
+		//x = (G ^ a) mod P
+		BigInteger x = (BigInteger.valueOf(G).pow(a)).mod(BigInteger.valueOf(P));
+		System.out.println("Alice's Public key(Ya) = " + x);
+		dos.writeInt(x.intValue());
+
+		//ka = (y ^ a) mod P
+		BigInteger ka=(BigInteger.valueOf(y).pow(a)).mod(BigInteger.valueOf(P));
+		System.out.println("Shared Key : "+ ka.intValue());
+	}
+}

ICS/Assignment3/BobDH.java

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+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.math.BigInteger;
+import java.net.Socket;
+import java.net.UnknownHostException;
+import java.util.Scanner;
+
+public class BobDH
+{
+	private static Socket soc;
+	private static Scanner sc;
+
+	public static void main(String[] args) throws UnknownHostException, IOException
+	{
+		int P,G;
+		int b;
+
+		soc = new Socket("127.0.0.1",8088);
+		System.out.println("Connected to "+soc.getRemoteSocketAddress());
+		DataInputStream dis = new DataInputStream(soc.getInputStream());
+		DataOutputStream dos = new DataOutputStream(soc.getOutputStream());
+		sc = new Scanner(System.in);
+
+		System.out.print("Enter Modulus (P) Prime Number: ");
+		P = sc.nextInt();
+		System.out.print("Enter Base (G) Primitive Root of P: ");
+		G = sc.nextInt();
+
+		dos.writeInt(P);
+		dos.writeInt(G);
+
+		System.out.print("Enter Private key : ");
+		b = sc.nextInt();
+
+		//y = (G ^ b) mod P
+		BigInteger y = (BigInteger.valueOf(G).pow(b)).mod(BigInteger.valueOf(P));
+		System.out.println("Bob's Public key(y)= " + y.intValue());
+		dos.writeInt(y.intValue());
+
+		//kb = (x ^ b) mod P
+		int x = dis.readInt();
+		System.out.println("Alice's Public key(Ya) = " + x);
+		BigInteger kb = (BigInteger.valueOf(x).pow(b)).mod(BigInteger.valueOf(P));
+
+		System.out.println("Shared Key: " + kb.intValue());
+		soc.close();
+	}
+}