Instant Messaging Application Requirements
==========================================

Overview
--------
Your team is to implement the protocol you designed and presented for
PS4.  You may implement a "stripped-down" version of your protocol if
you wish, but you must provide authentication, integrity, and
confidentiality of user and server messages (if a server is present).
Users must be authenticated using only a username and password.



Platform & Interface
--------------------
Your implementation must be in Java and the client portion must function
under the Java 6 Runtime Environment/SDK on your Linux server.

Your IM client must provide a console interface which can function over
an SSH connection.  In this interactive, text-based interface, your
client must accept the following commands:

  list
  send USER MESSAGE

the 'list' command should display all users currently signed into the
system.  The 'send' command sends the user USER a message, MESSAGE.  

If a server is used, the client should read server connection
information (IP, ports, etc) from a configuration file and upon
starting, it should immediately attempt to connect to the server.  Users
should be prompted at startup for their username and password.

You may use third-party libraries to implement this text interface, so
long as you provide all such libraries with your submission (and do not
break copyright law in doing so).  Also any interface must operate
properly over an ssh connection without the need for special tunnels or
complicated terminal settings.


Misc
----
The security features of your protocol implementation will provide you
with more base points.  In particular, if you support
resistance to denial of service attacks, end-points hiding, perfect
forward secrecy, protection for weak passwords, and/or message secrecy
against a malicious server, you will gain more points.