Anonymising virtual router

This SAÉ (paired with the event-driven programming module) requires designing and implementing from scratch an anonymous communication system between several clients, using distributed virtual routers. Anonymity relies on onion routing: chains of routers where each router only knows its direct neighbours (previous and next), without ever seeing the full origin of the message. It is how Tor (The Onion Router) works, reproduced at the scale of a student project.

The architecture is built on three roles. A master server defines the topology and distributes the keys: it receives each router's listening port and public key, then hands out the public keys to the clients. The clients build “onion” messages: they pick a random path (for example three routers) and stack several layers of encryption (layer 3, encrypted with router 3's key, contains the final message; layer 2, encrypted with router 2's key, contains router 3's address and layer 3; and so on). The routers decrypt a single layer, discover the address of the next hop and forward the rest.

In practice, the system has multiple routers and is deployed on at least two machines (Linux and Windows VMs for testing). Communication relies on TCP/UDP sockets in Python, simultaneous connections are handled with threads (multi-client server, dynamic ports), and a simplified asymmetric encryption scheme (public/private key pair per router) has to be coded by hand, without any cryptography library. Routing tables, keys and anonymised logs are stored in a MariaDB database. The client and the master have Qt graphical interfaces: the client handles connection and non-blocking message sending, the master displays the network, routes, logs and key distribution.

The project requires fully manual development (no auto-generated code), a clear and commented code structure, a mandatory Git repository, and a video demo showing traffic anonymisation. By its nature (anonymisation, layered encryption, Tor-style routing), it has a strong cybersecurity dimension.

Design and implement an anonymous communication system between several clients using virtual routers, guaranteeing anonymity through onion routing (chains of routers where each router only knows its direct neighbour), on a distributed network.