Name: clC74495 Date: 07/31/98


In the following source code, there are a "new ObjectOutputStream"
and a "new ObjectInputStream" statement. If you change their order,
the program will block!

(Further instructions after this code sample.)

import java.io.*;
import java.math.*;
import java.net.*;
import java.security.*;
import java.security.interfaces.*;

import ubilab.krypto.Protocol2withDSA;


public
class TestKeyExchangeServer
{
public
static
void
main( String[] args )
{
InputStream inputStream;
OutputStream outputStream;
ObjectInputStream oInputStream;
ObjectOutputStream oOutputStream;

int code;
int port = 1500;
ServerSocket serverSocket;
Socket connection;

KeyPairGenerator keyGen;
KeyPair keyPair;
DSAPrivateKey privateKey;
DSAPublicKey publicKey;

byte[] id;

Protocol2withDSA keyExchange;


try
{
keyGen = KeyPairGenerator.getInstance( "DSA" );
keyGen.initialize( 1024, new SecureRandom() );

keyPair = keyGen.generateKeyPair();

privateKey = (DSAPrivateKey)keyPair.getPrivate();
publicKey = (DSAPublicKey)keyPair.getPublic();
System.out.println( "Keys generated" );
id = ( publicKey.getY() ).toByteArray();

serverSocket = new ServerSocket( port );
connection = serverSocket.accept();
System.out.println( "Connection established" );

inputStream = connection.getInputStream();
outputStream = connection.getOutputStream();
System.out.println( "Streams established" );

oOutputStream = new ObjectOutputStream( outputStream );
System.out.println( "Object output stream established" );
oInputStream = new ObjectInputStream( inputStream );
System.out.println( "Object input stream established" );

// in practice, a CA already has the public key
oOutputStream.writeObject( publicKey );
oOutputStream.flush();
System.out.println( "Public key written" );

// in practice, you get the public key from a CA
publicKey = (DSAPublicKey)oInputStream.readObject();
System.out.println( "Public key read" );

keyExchange = new Protocol2withDSA( false, inputStream,
outputStream, privateKey, publicKey,
id, ( publicKey.getY() ).toByteArray() );
System.out.println( "KeyExchange instance created" );
keyExchange.performProtocol();

System.out.println( new BigInteger(
keyExchange.toByteArray() ) );


connection.close();
}
catch ( Exception e )
{
System.err.println( e );
}
}
}

-----

Put all the files (attachments) that don't start with "Test" in a folder called
krypto within a folder called ubilab, and compile them. Next, follow these
steps:

1. java TestKeyExchangeServer &
2. java TestKeyExchangeClient

Then it doesn't continue after the connection provided the input and the
output stream.

3. Change the instantiation order in both ther server and the client to
oOutputStream = new ObjectOutputStream( outputStream );
oInputStream = new ObjectInputStream( inputStream );
4. Suddenly it works - at least that part :)

(Review ID: 36112)
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