Ciphered streams problem

[Jakub Stuglik]

Hi. I've got a problem with the RSA ciphered streams. Here is a piece of
code that generates an exception :

KeyPairGenerator gen = KeyPairGenerator.getInstance("RSA");
System.out.print("Generating the RSA key pair...");
KeyPair kp = gen.generateKeyPair();
System.out.println("done.");
Cipher ci = Cipher.getInstance("RSA");
ci.init(Cipher.ENCRYPT_MODE,kp.getPublic());
Cipher cid = Cipher.getInstance("RSA");
cid.init(Cipher.DECRYPT_MODE,kp.getPrivate());
CipherOutputStream cout = new CipherOutputStream(new
FileOutputStream("rsa.dat"),ci);
ObjectOutputStream oout = new ObjectOutputStream(cout);
oout.writeObject(kp.getPrivate().toString());
oout.flush();
oout.close();
CipherInputStream cin = new CipherInputStream(new
FileInputStream("rsa.dat"),cid);
ObjectInputStream oin = new ObjectInputStream(cin); // Exception here
System.out.println(oin.readObject());
oin.close();

The exception is EOFException and it's not very weird because the file
"rsa.dat" is empty after writing to it!! It happens only if object is "big"
( when I try to write some short String, for example, everything's ok ).
When I tried to write an unciphered output ( without using
CipheredOutputStream ) it went well of course.
My question is : can anybody tell me why it happens? What should I do to
write "big" objects to ciphered output stream using ObjectOutputStream
properly?
Thanks for any requests.

Kuba