Cryptonomicon

Let's check out some Java Cryptography,
considering both symmetric and asymmetric algorithms.

We implement a client and server that mimic how SSL works, where the client uses
the server's public key to asymmetrically encrypt and transfer a secret key, which is then
used by both sides to encrypt messages using a symmetric cipher.

href="https://aptframework.dev.java.net/jelly/cryptonomical.html">

border="0" width="32" height="32" align="left" hspace="8"/>
Click here to read "Cryptonomical, the secret story"

Part of the "Jelly Beans" part of a trilogy in 42 parts

Code Snippet

The client connects to the server port, negotiates a key exchange, and
then communicates securely.

public class CryptonomicalClient extends Thread {
    CryptonomicalSocket cryptoSocket;
    ...
    public void run() {
        try {
            String publicKey = cryptoSocket.sendRequest(cryptoRequest);
            cryptoSocket.setEncodedPublicKey(publicKey);
            cryptoSocket.generateSecretKey();
            String encryptedSecretKey = cryptoSocket.encryptSecretKey();
            String response = cryptoSocket.sendRequest(encryptedSecretKey);
            if (!response.equals(cryptoAcknowledge)) throw new RuntimeException();
            cryptoSocket.setEncrypt(true);
            process();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            cryptoSocket.close();            
        }
    }
    
    protected void process() throws Exception {
        String response = cryptoSocket.sendRequest("ALL YOUR BASE ARE BELONG TO US.");
        logger.info(response);
    }        
}

Once key change has been accomplished, we can securely send the
server a test message
in process().

PS. The title of this article is of course a tribute to Neal Stephenson's book
Cryptonomicon,
which is on my bedside table right now.