Thread: my encrypting simple client to server program unable to get the key from client

hi,

so currently i am still trying the send the aes key encrypted with private and public key from keystore but it keep java.crypto.badpaddingexception blocktype mismatch:0
nullpointerexception

so i tried to print out the aes keys on both size and realized i am unable to get the aes key from the client so please take a min and help me to look through my code.

my Client

import java.net.*;
import java.io.*;
 import javax.crypto.*;
 import javax.crypto.spec.*;
 import java.security.*;
 import sun.misc.*;
 import java.security.cert.Certificate;
import java.security.cert.CertificateFactory;
import java.security.spec.*;
public class myClient
{  private Socket socket              = null;
   private DataInputStream  console   = null;
   private DataOutputStream streamOut = null;
 
 
   public myClient(String serverName, int serverPort,String clientuser,String serveruser) throws Exception
   {  System.out.println("Establishing connection. Please wait ...");
      try
      {  socket = new Socket(serverName, serverPort);
         System.out.println("Connected: " + socket);
         start();
      }
      catch(UnknownHostException uhe)
      {  System.out.println("Host unknown: " + uhe.getMessage());
      }
      catch(IOException ioe)
      {  System.out.println("Unexpected exception: " + ioe.getMessage());
      }
      String line = "";
	    //get public certificate.(signed)
	  //get private key
 
 
CertificateFactory certfac = CertificateFactory.getInstance("X.509");
	// //get CA CERT gen cert. closest filestream
	// FileInputStream CA = new FileInputStream ("rootca.cer");
	// Certificate CACert = certfac.generateCertificate(CA);
	// CA.close();
	// //ca cert get public
	// PublicKey CACertPub=CACert.getPublicKey();
 
 
	//need name for server user, generate server cert
			FileInputStream server = new FileInputStream (serveruser+".crt");
		Certificate serverCert = certfac.generateCertificate(server);
			ByteArrayOutputStream buffer = new ByteArrayOutputStream();
	//generating the signature of the server cert
int nRead;
byte[] data = new byte[1024];
 
while ((nRead = server.read(data, 0, data.length)) != -1) {
  buffer.write(data, 0, nRead);
}
buffer.flush();
	server.close();
 
 
 
 
	//
	//verifying the Server Cert with 
	 // File file = new File(serveruser+".sig");
// byte[] sigBytes = new byte[(int) file.length()];
 // FileInputStream fis = new FileInputStream(file);
 // fis.read(sigBytes);
 // fis.close();
	// boolean veri=verifySig(data,CACertPub,sigBytes);
 
 
 
 
 
	  // if(veri==true){
 
	//  	get private key from .keystore	  
	PrivateKey ClientPriv=(PrivateKey)getKeyfromkeystore(clientuser);
	  Key AESKey=AESGen();
	  byte[] objectbyte=changetobyte(AESKey);
	  System.out.println(asHex(AESKey.getEncoded()));
 
  //send aes key in encrypt format
	  byte[] aessend=RSAEncryption(serverCert.getPublicKey(),ClientPriv ,objectbyte);
 
		streamOut.write(aessend,0,aessend.length);
		streamOut.flush();
		byte[] signatureaes=signData(aessend,ClientPriv);
		streamOut.writeUTF(AESEncrypt(AESKey,asHex(signatureaes)));
		streamOut.flush();
	 while (!line.equals("..bye"))
      {  try
 
         {
 
 
		 line = console.readLine();
		//encrypt line
		if (line.length()<200){
		String encryptedline =AESEncrypt(AESKey,line);
		//sign the  encrypted line
		byte[] signature=signData(getfromhex(encryptedline),ClientPriv);
		//send line over
 
			streamOut.writeUTF(line);
            streamOut.flush();
			streamOut.writeUTF(AESEncrypt(AESKey,asHex(signature)));
            streamOut.flush();
		//send the signature over
		}
		else System.out.println("ERROR message too long");
 
         }
         catch(IOException ioe)
         {  System.out.println("Sending error: " + ioe.getMessage());
         }
      }
	  // }else
	  // System.out.println("Error, Someone is Impersonating the person you are talking to.");
   }
   public void start() throws IOException
   {  console   = new DataInputStream(System.in);
      streamOut = new DataOutputStream(socket.getOutputStream());
   }
   public void stop()
   {  try
      {  if (console   != null)  console.close();
         if (streamOut != null)  streamOut.close();
         if (socket    != null)  socket.close();
      }
      catch(IOException ioe)
      {  System.out.println("Error closing ...");
      }
   }
   public static void main (String args[]) throws Exception
   {  myClient client = null;
      if (args.length != 4)
         System.out.println("Usage: java myClient host port yourname serverusername");
      else
         client = new myClient(args[0], Integer.parseInt(args[1]),args[2],args[3]);
   }
 
 
  public static byte[] signData(byte[] data, PrivateKey key) throws Exception {
    Signature signer = Signature.getInstance("SHA1withRSA");
    signer.initSign(key);
    signer.update(data);
    return (signer.sign());
  }
   public byte[] changetobyte(Key AESKey){
   	  Object Aesobj= new Object();
	  Aesobj = (Object)AESKey;
	  byte[] objectbyte =null;
try{	  
	//Change Object to byte format  
	  ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutput out = null;
  out = new ObjectOutputStream(bos);   
  out.writeObject(Aesobj);
  objectbyte = bos.toByteArray();
  out.close();
  bos.close(); }catch(Exception e){
	System.out.println(e);
  }
   return objectbyte;
   }
     public Key AESGen(){
  //generate aes
  Key AESKey = null;
  try{
  KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
    keyGenerator.init(128);
    AESKey = keyGenerator.generateKey();
 
	}
	catch(Exception e){
		System.out.println(e);
	}
	return AESKey;
  }
 
 
  public Key getKeyfromkeystore(String alias){
  final String keystoreName = "./.keystore";
        final String keystorePassword = "123123123aA";
        KeyStore ks = null;
		Key key=null;
  try{
   ks= KeyStore.getInstance("jks");
        ks.load(new FileInputStream(keystoreName), keystorePassword.toCharArray());
         key = ks.getKey(alias+"signed", keystorePassword.toCharArray());
	}catch (Exception e){
	System.out.println(e);
	}
		 return key;
  }
 
     		   public static boolean verifySig(byte[] data, PublicKey key, byte[] sig) throws Exception {
    Signature signer = Signature.getInstance("SHA1withRSA");
    signer.initVerify(key);
    signer.update(data);
    return (signer.verify(sig));
 
  }
 
     	 public byte[] RSAEncryption(PublicKey ServerPub,PrivateKey ClientPriv,byte[] Aestxt){
  //encrypts the AES key with private key then public key
  byte[] seccipher = null;
  try{
  Cipher cipher = Cipher.getInstance("RSA/ECB/NoPadding");
  cipher.init(Cipher.ENCRYPT_MODE,ClientPriv);
  byte[] firstcipher=cipher.doFinal(Aestxt);
  cipher.init(Cipher.ENCRYPT_MODE,ServerPub);
 seccipher= cipher.doFinal(firstcipher); 
  }
  catch(Exception e){
	System.out.println(e);
  }
  return seccipher;
 
  }
 
 
  public String AESEncrypt(Key AESKey, String PlainTxt){
 //get instance of AES
 //Encrypt data
 byte[] ciphertxt = null;
 try{
  Cipher c = Cipher.getInstance("AES");
//SecretKeySpec k =new SecretKeySpec(AESKey, "AES");
c.init(Cipher.ENCRYPT_MODE, AESKey);
byte[] Ptxt=getfromhex(PlainTxt);;
ciphertxt=c.doFinal(Ptxt);
	}
	catch(Exception e){
		System.out.println(e);
	}
   return asHex(ciphertxt);
  }
 
  public static byte[] getfromhex(String s){
	int len =s.length();
	byte[] data=new byte[len/2];
for(int i=0;i<len;i+=2){
data[i/2] = (byte)((Character.digit(s.charAt(i),16)<<4) + Character.digit(s.charAt(i+1),16));
 
}
 return data;
 
}
 
    public static String asHex (byte buf[]) {
  //Obtain a StringBuffer object
      StringBuffer strbuf = new StringBuffer(buf.length * 2);
      int i;
 
      for (i = 0; i < buf.length; i++) {
          if (((int) buf[i] & 0xff) < 0x10)
             strbuf.append("0");
             strbuf.append(Long.toString((int) buf[i] & 0xff, 16));
       }
       // Return result string in Hexadecimal format
       return strbuf.toString();
  }
 
 
 
}

My server

import java.net.*;
import java.io.*;
 import javax.crypto.*;
 import javax.crypto.spec.*;
 import java.security.*;
 import sun.misc.*;
 import java.security.cert.Certificate;
import java.security.cert.CertificateFactory;
import java.security.spec.*;
 
public class myServer
{  private Socket          socket   = null;
   private ServerSocket    server   = null;
   private DataInputStream streamIn =  null;
 
   public myServer(int port,String User,String Clientuser) throws Exception
    	 {try{
		 System.out.println("Binding to port " + port + ", please wait  ...");
         server = new ServerSocket(port);
         System.out.println("Server started: " + server);
         System.out.println("Waiting for a client ...");
         socket = server.accept();
         System.out.println("Client accepted: " + socket);
         open();
         boolean done = false;
 
		 //get Public Cert from Client
	 //convert to public cert.
 
 
		// Generate a certificate from that file
		Certificate ClientCert = getcert(Clientuser);
//getting the public key 
	PublicKey ClPubkey=ClientCert.getPublicKey();
 
// //verifying the Client Cert
	// boolean veri=verifySig(data,CACertPub,sigBytes);
 
 
		// //get CA,certificate
	// Certificate CACert = getcert(CA);
 
	// //ca cert get public
	// PublicKey CACertPub=CACert.getPublicKey();
 
 
//get the user of my server cert
	//need name
	Certificate serverCert = getcert(User);
 
 
							//get private key from .keystore		
		 PrivateKey ServerPriv=(PrivateKey)getKeyfromkeystore(User);
		 byte[] mybyte= new byte[5000];
		 //get aes string
		int rsize=  streamIn.read(mybyte);
		byte[] encryptedobj = new byte[rsize];
		for(int i=0; i==rsize;i++){
		encryptedobj[i]=mybyte[i];
		}
 
 
		//decrypt it
		byte[] aesobj=DecryptRSA(ServerPriv,serverCert.getPublicKey(),encryptedobj);
 
		//convert string aes to object.
		ByteArrayInputStream bis = new ByteArrayInputStream(aesobj);
ObjectInput in = null;
  in = new ObjectInputStream(bis);
  Object o = in.readObject(); 
 bis.close();
  in.close();
		Key AESKey=(Key) o;
 
					//get signature
 
		  System.out.println(asHex(AESKey.getEncoded()));
 
		String sigofobjencrypted=streamIn.readUTF();
		//decrypt signature
 
		String sigofobj=AESDecrypt(AESKey,getfromhex(sigofobjencrypted));
		//verify signature with encryptedobj(get sig),CLient PublicKey and the recieved signature
	//	verifySig(encryptedobj.getBytes(),ClientCert.getPublicKey(),sigofobj.getBytes());
 
 
 
		String line="";
		String encryptedline = "";
 
			String encyptedsignature = "";
 
         while (!done){  
			try{  			//verifys the line
			encryptedline = streamIn.readUTF();
			 encyptedsignature = streamIn.readUTF();
		//	 signatureString=AESDecrypt(AESKey,getfromhex(encyptedsignature));
			//if verifying failed, print nothing
			//verifying if Clientpublic key of the encrypted line with the signature that was send
				//if(verifySig(encryptedline.getBytes(),ClPubkey,signatureString.getBytes())==true){
				line=AESDecrypt(AESKey,getfromhex(encryptedline));
 
					System.out.println(line);
					done = line.equals("..bye");
				//}
			}	
 
            catch(IOException ioe)
				{  done = true;
				}
//			else System.out.println("ERROR, its not"+Clientuser);
 
				}	
 
			}
			catch(IOException ioe){
				System.out.println(ioe);
			}
   close();
   }
 
 
 
 
   public Certificate getcert(String Clientuser){
   FileInputStream Clientpersonc = null;
   		CertificateFactory certfac =null;
		Certificate ClientCert = null;
		try{
    Clientpersonc = new FileInputStream (Clientuser+".crt");
		// Generate a certificate from that file
		certfac = CertificateFactory.getInstance("X.509");
		//convert to public cert.
		// Generate a certificate from that file
		ClientCert = certfac.generateCertificate(Clientpersonc);
   					Clientpersonc.close();}
					catch(Exception e){
						System.out.println(e);
					}
   return ClientCert;
   }
 
   public void open() throws IOException{  
   streamIn = new DataInputStream(new BufferedInputStream(socket.getInputStream()));
		}
   public void close() throws IOException
   {  if (socket != null)    socket.close();
      if (streamIn != null)  streamIn.close();
   }
   public static void main(String args[])
   {  myServer server = null;
      try{
	  if (args.length != 3)
         System.out.println("Usage: java myServer port yourname Clientname");
      else
         server = new myServer(Integer.parseInt(args[0]),args[1],args[2]);
		}
	catch(Exception e){
		System.out.println(e);
		}
   }
 
 
 public Key getKeyfromkeystore(String alias){
  final String keystoreName = "./.keystore";
        final String keystorePassword = "123123123aA";
        KeyStore ks = null;
		Key key=null;
  try{
   ks= KeyStore.getInstance("jks");
        ks.load(new FileInputStream(keystoreName), keystorePassword.toCharArray());
         key = ks.getKey(alias+"signed", keystorePassword.toCharArray());
	}catch (Exception e){
	System.out.println(e);
	}
		 return key;
  }
 
 
  public String AESDecrypt(Key AES,byte[] encrypted){
  //decrypt aes
  String text="";
	try{//some try catch problem
			Cipher cipher = Cipher.getInstance("AES/ECB/NoPadding");
			cipher.init(Cipher.DECRYPT_MODE,AES);
			byte [] txt=cipher.doFinal(encrypted);
			text=asHex(txt);
 
		}
		catch(Exception e){
			System.out.println(e);
		}	
		return (text);
  }  
 public byte[] DecryptRSA(PrivateKey Serverpriv, Key ClientPub,byte[] CTxt){
   //Decrypt with private key
   //decrypt with public key
   byte[] aesbyt = null;
	try{
		Cipher cipher = Cipher.getInstance("RSA");
		//init with private key   
		cipher.init(Cipher.DECRYPT_MODE,Serverpriv);
		byte[] Cipher1=cipher.doFinal(CTxt);
 
		//init it with serverpublic key   
		cipher.init(Cipher.DECRYPT_MODE,ClientPub);
		aesbyt=cipher.doFinal(Cipher1);
		}
 
	catch(Exception e){
			System.out.println(e);
		}
		return aesbyt;
	}
 
   		   public static boolean verifySig(byte[] data, PublicKey key, byte[] sig) throws Exception {
    Signature signer = Signature.getInstance("SHA1withRSA");
    signer.initVerify(key);
    signer.update(data);
    return (signer.verify(sig));
  }
 
    public static String asHex (byte buf[]) {
 
  //Obtain a StringBuffer object
      StringBuffer strbuf = new StringBuffer(buf.length * 2);
      int i;
 
      for (i = 0; i < buf.length; i++) {
          if (((int) buf[i] & 0xff) < 0x10)
             strbuf.append("0");
             strbuf.append(Long.toString((int) buf[i] & 0xff, 16));
       }
       // Return result string in Hexadecimal format
       return strbuf.toString();
  }
 
 
 
   public static byte[] getfromhex(String s){
	int len =s.length();
	byte[] data=new byte[len/2];
for(int i=0;i<len;i+=2){
data[i/2] = (byte)((Character.digit(s.charAt(i),16)<<4) + Character.digit(s.charAt(i+1),16));
 
}
 return data;
 
}
 
 
}

Capture.JPGCapture1.JPG

heres both of them.

System.out.println("fufiffofo");
//decrypt it
byte[] aesobj=DecryptRSA(ServerPriv,serverCert.getPublicK ey(),encryptedobj);
System.out.println("fufiffofo");

i tried to debug it using print ln and this was between the nonsense

ok sorry here the error

C:\Users\hp\Desktop\project>java myServer 80 alice bob
Binding to port 80, please wait ...
Server started: ServerSocket[addr=0.0.0.0/0.0.0.0,port=0,localport=80]
Waiting for a client ...
Client accepted: Socket[addr=/127.0.0.1,port=59886,localport=80]
fufiffofo
javax.crypto.BadPaddingException: Blocktype mismatch: 0
fufiffofo
java.lang.NullPointerException

C:\Users\hp\Desktop\project>

C:\Users\hp\Desktop\project>java myClient 127.0.0.1 80 bob alice
Establishing connection. Please wait ...
Connected: Socket[addr=/127.0.0.1,port=80,localport=59886]
d3cbf144b7bc32a18f29d598d9977354
Exception in thread "main" java.lang.NullPointerException

C:\Users\hp\Desktop\project>

the problem is sending the decrypting the AESKey after being encrypted with rsa private and public key from certificate

ok i found the error here

//remove additional byte
byte[] mybyte= new byte[300];
//get aes string
int rsize= streamIn.read(mybyte);

byte[] encryptedobj = new byte[rsize];
for(int i=0; i==rsize;i++){
encryptedobj[i]=mybyte[i];

}

these code does not transfer the value of the byte to encryptedobj somehow.. any ideas on how to fix it?

thanks for the help so far.

nah i am asking how do i copy the value of the byte array to another byte array using a for loop

i am getting bytes cannot be dereferenced