It is a chat application that demonstrates asymmetric and symmetric encryption.

It is developed with python version 3.9.6 and requirements.txt contains required libraries.

The server and the client generate public/private keys at runtime and exchange them, then server uses client's public key to encrypt a randomoly generated session key that will be shared with the client.

After this process the client decrypts it with a private key and uses secret to encrypt/decrypt messages using AES in Cipher FeedBack (CFB) mode. The server can handle multiple client connections, and it doesn't log the messages keeping clients communication secure.

➜  python3 server.py -p 9443
[+] Running on host: 127.0.0.1
[+] Running on port: 9443

it requires three parameters, -s server ip, -p server port number, -u username:

➜  python3 client.py -s 127.0.0.1 -p 9443 -u sahnawaz
[+] Connected successfully.
[+] Exchanging keys.
[+] Getting public key from the server
[+] Sending public key to server
[+] Exchange completed!
[+] Initial set up had been completed!
[+] Now you can start to exchange messages

TERMINATE
[+] All connections had been terminated
[+] Server is shut down

EXIT
# Message at server
[+] sahnawaz left the server.

• install dependent python packages from requirements.txt:

  $ pip install -r requirements.txt

• starting server

  ➜ python3 server.py -p 9443                         
  [+] Running on host: 127.0.0.1
  [+] Running on port: 9443

• client-1 joining from other terminal with generating and exchanging keys:

  ➜ python3 client.py -s 127.0.0.1 -p 9443 -u sahnawaz
  [+] Connected successfully.
  [+] Exchanging keys.
  [+] Getting public key from the server
  [+] Sending public key to server
  [+] Exchange completed!
  [+] Initial set up had been completed!
  [+] Now you can start to exchange messages

• key files are written to path for client and server:

  ├── README.md
  ├── client.py
  ├── client_private_key.pem     -----> client private key
  ├── client_public_key.pem      -----> client public key
  ├── requirements.txt
  ├── server.py
  ├── server_private_key.pem    -----> server private key
  └── server_public_key.pem     -----> server public key

• client-2 joining from third terminal:

  ➜ python3 client.py -s 127.0.0.1 -p 9443 -u Ira 
  [+] Connected successfully.
  [+] Exchanging keys.
  [+] Getting public key from the server
  [+] Sending public key to server
  [+] Exchange completed!
  [+] Initial set up had been completed!
  [+] Now you can start to exchange messages

• server side communication info for client-1 (sahnawaz) & client-2 (Ira):

  [+] New connection. Username: sahnawaz
  [+] Client public key had been received
  [+] Secret key had been sent to the client
  [+] New connection. Username: Ira
  [+] Broadcast message:  New person joined the room. Username: Ira
  [+] Client public key had been received
  [+] Secret key had been sent to the client

• message exchanges between client-1 & client-2 with server side info:

  # client-2
  2023-06-25 09:35:24 Ira: Hi
  Hello Ira
  
  # client-1
  Hi
  2023-06-25 09:35:36 sahnawaz: Hello Ira
  
  # server side
  2023-06-25 09:35:24 Mesage exchanged
  2023-06-25 09:35:36 Mesage exchanged

• session closure and server termination

  # client-2
  EXIT
  
  # client-1
  EXIT
  
  # server side
  [+] Ira left the server.
  [+] sahnawaz left the server.
  TERMINATE
  [+] All connections had been terminated
  [+] Server is shut down