Virtual Private Network (VPN)

Philosophy

A Virtual Private Network enables users to send and receive data across a shared or public network as if their devices were directly connected through a private network. This project is a proof of conecpt of a simple VPN server and client exchange data through an encrypted private network and data transferred between node A and B without being decipherable by external parties.

Figure 1: Procedural Diagram of VPN Data Exchange

Algorithm

1. Establishing a Connection

During boot, the server listens for a connection, and a client requests to connect to a the server, after which the two nodes negotiate on a cipher out of supported ciphers. These include (128 192, 256)-bit AES, (112, 224, 448)-bit Blowfish, and 56-bit DES encryption.

2. Diffie-Hellman Key Exchange

After negotiating possible ciphers, the client / server pair generate private and public key pairs, hashes the keys, and uses Diffie Hellman key exchange to exchange each other's public and private keys and establish authenticity.

3. Data Transfer

The server will then listen for any incoming requests. The user will be prompted for a message and any input will be transferred from the client to a server. Upon reception of the data, the server will validate the HMAC hash and display the data on the console.

Running the Server

Make sure all the required modules are installed. Using python3 run the server.py and client.py in different terminal windows.

Installing Requirements on a Virtual Environment

python3 -m venv .venv
source .venv/bin/activate
pip install -r requirements.txt

Running the Server

$ python3 server.py

Running the Client

$ python3 client.py

Example Session

Server side

$ python3 server.py
Listening on ubuntu:4600
New client: 127.0.0.1:46596
Negotiating the cipher
We are going to use AES256
Negotiating the key
The key has been established
Received: hello
Received: bye

Client side

$ python3 src/projects/vpn/client.py
Connected to ubuntu:4600
Negotiating the cipher
We are going to use AES256
Negotiating the key
The key has been established
Enter message: hello
Server says: olleh
Enter message: bye
Server says: eyb
Enter message: \quit

Acknowledgements

This project is a modified version of a similar VPN project in Luther College's 2019 CS-460 Information Assurance and Security course implemented by me.