Secure Sockets

• The are needed because Ethernet is a broadcast medium (sniffers).
• Do not write your own!
• Public Key encryption consists of public and private key pairs. One can be used to decode something encrypted with the other.
• Private key encryption uses only one key which both sides must know. It runs much faster.
• Java has many encryption algorithms built-in.
• Java CipherSuites combine stream encryption (e.g., RC4) with authentication cyphers (e.g., RSA). Typically, PKE is used to exchange a private key which is then used to encode the stream.

import java.net.*;
import java.io.*;
import java.security.*;
import javax.net.ssl.*;

public class HTTPSClient {
    
  public static void main(String[] args) {
    
    if (args.length == 0) {
      System.out.println("Usage: java HTTPSClient host");
      return;
    }       
    
    int port = 443; // default https port
    String host = args[0];
    
    try {     

      //Uses the factory design pattern.
      SSLSocketFactory factory 
        = (SSLSocketFactory) SSLSocketFactory.getDefault();
       
      SSLSocket socket = (SSLSocket) factory.createSocket(host, port);

      // enable all the suites
      String[] supported = socket.getSupportedCipherSuites();
      socket.setEnabledCipherSuites(supported);

      Writer out = new OutputStreamWriter(socket.getOutputStream());
      // https requires the full URL in the GET line
      out.write("GET http://" + host + "/ HTTP/1.1\r\n");
      out.write("\r\n");
      out.flush(); 

      // read response
      BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
      int c;
      while ((c = in.read()) != -1) {
        System.out.write(c);
      }
      
      out.close();                  
      in.close();
      socket.close();
      
    } 
    catch (IOException e) {
      System.err.println(e);
    }
    
  }
  
}