CS 342 - 11/16/17

Exam 1 Results

Count   153
Max      98
Min      16
Ave      69.43
Median   70
St.Dev.  14.24

90's    4
80's   32
70's   41
60's   43
50's   16
40's   12
30's    3
20's    1
10's    1


Protocol for Echo Client

    Client                    Server
    -------                   -------

      Get message
       Send to Server   --->   Receive Message
                                Display Message
       Receive Message  <---   Send Message
      Display message

     Repeat                    Repeat


Possible Protocol for Battleship

  Player 1                      Player 2
  --------                      --------

   Determine location
   Send                --->      Receive
                                 Determine Hit/Miss & UPdate GUI
   Recieve             <---      Send
   Update GUI
   End Turn            --->
                                 Determine location
   Receive             <---      Send
   Determine Hit/Miss 
     & UPdate GUI
   Send                --->      Receive
                                 Update GUI
                       <---      End Turn

   Repeat                        Repeat


For Project 5 and Supporting Document 4

  Create a Networked Chat with Encryption

Design Document (Suporting Document 4) 
     Due in first half of 14th week

Programs Due in second half of 15th week

Network Chat would use a central server that all clients connect
   to.

  A message from Client X to Client Y would pass first
    from Client X to the server, then from the server to Client Y



Tasks associated with the Server:
   1.   Allow new clients to connect
        - Server must notify all the other clients of the 
              new Clients
        - As Clients disconnect, the server must notify all
              other Clients of the disconnection.

   2.   Acts as the mediator of the message sending
        Monitoring each socket for message input ane then
          forwarding the message along to the proper client.

   3.   Public Key distribution would be sent to all other
          Clients (Perhaps this is really Tasks 1b.) 


Tasks Associated with the Client
   1.  Create the Public/private key pairs

   2.  Connect to the server.

   3.  Monitor the server for incoming messages.
         -  Info about new Clients or removal of existing Clients
         -  Messages send to this Client

   4.  Send a message to the server for Client Y

   5.  Encrypt messages being sent
  
   6.  Decrypt messages received


RSA Encryption/Decryption

 Most of the following is from:
    http://www.geeksforgeeks.org/rsa-algorithm-cryptography/

   Public Key consists of two values:  n, e
   Private Key consists of two values: n, d


   Encrypt Message M :   M^e % n  ===> M'

   Decrypt M'        :   M'^d % n ===> M

   Start with 2 prime: p, q

   Calculate n:  p * q   

   Calculate phi:  (p-1)*(q-1)

   Calculate/Select e
        must be an integer
        must be "relatively-prime" with phi 
        must be in range 1 < e < phi

   Determine/Select d
        d = (k*phi + 1) / e for some integer k
               where e must divide (k*phi + 1) evenly
               ((k*phi + 1) must be a multiple of e)

   Mutliple values could be used for e or d, sometimes the
     Xth smallest value is used to add extra security/randomness

Assume the message is: 

    Meet me at the CS Lounge at noon.

Blocking Size  ==> Characters per message

Messages to encrypt are as follows if blocking size is 2:

    Me   =>  Numeric value ==>    
    et
     m
    e 
    ....

There would be 17 different Encrypted values to be sent.

How to we send these values from client X to Client Y?

  We will send an object that has a integer vector?


Messages will be sent as Character Strings

1.  First character indicate the "message type"

Message Type one:  New Client

   Char 1:  a
   Next:    Client Id  (must be unique)
   Next:    e value for client as a ASCII decimal value
   Next:    space
   Next:    n value for the client as a ASCII decimal value

Message Type two: Remove Client

   Char 1:   b
   Next:     Client Id  (same from Message Type 1)

Message Type three:  Send Message

   Char 1:   c
   Next:     To Client Id  (same from Message Type 1)
   Next:     From Client Id  (same from Message Type 1)
   Next:     encrypted value as a ASCII decimal value
   Next:     Space
    Repeat last 2 for as amany as needed