/**
* * All the symmetric encryption and decryption occurs here. Ciphers must be instantiated and
* executing using the derivated keys from p1 and p2. From a text corpus client and server
* interchange some lines, all of them encrypted. The challenge for client is to decrypt and
* answer accordingly to server expectations.
*
* @throws IOException Communication errors will throw this one
* @throws ParseException Appears if something unexpected is received
*/
private void communicationPhase() throws IOException, ParseException {
// stream cipher is instantiated here!
streamCipher = new StreamCipher(sharedKey, prime, p1, p2);
// send ACK informing that we are ready to encrypt/decrypt
SpecsDoneRequest request = new SpecsDoneRequest(++counter);
log.debug("Message to send: [" + request.toJSON() + "]");
writer.write(request.toJSON().getBytes("UTF-8"));
writer.flush();
// Receive all text from Server
receiveAllLines();
// Reset the Shift Register prior to sending out CLIENT_TEXT messages
streamCipher.reset();
// Send all text to Server
sendAllLines();
// Wait for last server message
byte[] buff = new byte[BUFFER_SIZE];
reader.read(buff);
String reply = new String(buff, "UTF-8");
log.debug("Message received: [" + reply + "]");
CommDoneResponse response = new CommDoneResponse();
response.fromJSON(StringParser.getUTFString(reply));
// answers properly
CommDoneRequest doneRequest = new CommDoneRequest();
log.debug("Message to send: [" + doneRequest.toJSON() + "]");
writer.write(doneRequest.toJSON().getBytes("UTF-8"));
}
private void sendLine(long id, String line) throws IOException, ParseException {
String encrpytedMsg = streamCipher.encrypt(line);
TextRequest msgRequest = new TextRequest(id, encrpytedMsg, ++counter);
// Send TEXT Message Length
NextMessageLengthRequest lenRequest =
new NextMessageLengthRequest(id, msgRequest.toJSON(), ++counter);
log.debug("Message to send: [" + lenRequest.toJSON() + "]");
writer.write(lenRequest.toJSON().getBytes("UTF-8"));
writer.flush();
// Length Acknowledgement
byte[] buff = new byte[BUFFER_SIZE];
reader.read(buff);
String reply = new String(buff, "UTF-8");
log.debug("Message received: [" + reply + "]");
MessageLengthReceivedResponse lenResponse = new MessageLengthReceivedResponse();
lenResponse.fromJSON(StringParser.getUTFString(reply));
// Send TEXT Message
System.out.println("CLIENT_TEXT >>>>>>>>> ID: " + id);
System.out.println("Plain Text: \n" + line);
System.out.println("Cipher Text: \n" + encrpytedMsg);
log.debug("Message to send: [" + msgRequest.toJSON() + "]");
writer.write(msgRequest.toJSON().getBytes("UTF-8"));
writer.flush();
// Wait Acknowledgement of SERVER_TEXT_RECV
buff = new byte[BUFFER_SIZE];
reader.read(buff);
reply = new String(buff, "UTF-8");
log.debug("Message received: [" + reply + "]");
TextReceivedResponse txtResponse = new TextReceivedResponse();
txtResponse.fromJSON(StringParser.getUTFString(reply));
}
private String decrypt(String ciphertext) {
return streamCipher.decrypt(ciphertext);
}