Local Host

Encrypted Communication

Background

The goal of this assignment is to give you practical experience in using cryptographic libraries to

implement encryption functionality in your code, especially in regard to data in transit i.e.

network communications.

To this end you are provided with two pieces of code (server.c and client.c) written in the C

programming language. The code implements a simple socket communication program that

enables two machines (a client and a server) to make a connection to each other and send

messages.

Your objective in carrying out this assignment will be to modify the code to achieve the

following:

 Unlimited communication between the client and the server

 Termination of the connection when a specific message is sent from the client to the

server

 Encryption of the communication between the client and the server using any encryption

technique

Instructions

1. You will find attached the two pieces of C programming language code that implement the

socket program (One for the Client side and the other for the Server side).

2. You can run the program on any platform that works for you (I would suggest using Ubuntu

Linux). After compiling the code, you have to assign a port number (example; Port number =

5000, you can use any port number between 2000 and 65535) to the server when putting in

the command to run it. i.e.

./server 5000

On the client side, you need the host name or IP address of the machine on which the server is

running (if the host name or IP address is X) to run the client and connect to the server

./client X 5000

If you are running both programs on the same machine, the host name of the server will be

localhost

./client localhost 5000

NOTE: A tutorial will be given to explain the details of the program and demonstrate how to

compile and run the code. Please endeavour to attend the tutorial

3. The connection between the client and server closes after one message is sent, modify the

codes such that multiple messages can be sent between both sides without termination.

4. Modify the code to terminate the connection when the client sends the message “End

Session” to the server.

5. Modify the code such that communication between both the client and server is an encrypted

communication (Symmetric or Asymmetric)

6. During the encrypted communication the terminal should display the messages received both

before decryption and after decryption

NOTE: Implement any encryption technique you’ve learnt so far and use any C language

cryptographic library of your choice, preferably the one you identified in your previous

assignment.

Submission

1) Submit your modified code and a report (which should include screenshots of your results for

questions 3, 4, and 5) in separate files via Blackboard by the due date. No zipped files

allowed.