blackedoutchat

A decentralized chat program that uses the Tor network to remain anonymous and punch through NATs.

Architecture

TODO

TODO

This is a project that I worked on and dropped a year ago. I'm rebuilding it from scratch (started on 23rd April 2022).

UPDATE 2023: Messages can now be sent between clients but there is no mechanism to store messages yet.

• Tor process wrapper
  • Starting the process in a separate thread
  • Configuring Tor to use Unix sockets to not conflict with existing Tor instances
  • Other Tor configuration (data directory, etc.)
  • Change file permissions on data directory to satisfy Tor's requirements (chmod 700 seems to do the trick)
  • Ctrl+C and SIGTERM handler in parent process that will send Tor a SIGTERM before terminating
  • Asynchronous loop to monitor the condition of Tor (i.e. if it exits, then terminate the parent process for now)
• P2P connections
  • Unix socket to listen to incoming connections from Tor
  • Interface to accept connection requests to other peers
  • Global state to keep track of all connected peers
  • Authentication (to prove that the peer connecting to you is who they say they are)
    • You will send a random 256-bit token to the peer
    • Peer will send you the onion address that they claim to be and also the sign the token using their ed25519 key and send the signatture
    • You will verify the signature by deriving the ed25519 public key from the onion address
    • There is no need for you to prove who you are to them as they are the ones connecting to your onion address and Tor proves it internally
• Cryptography (post-quantum hybrid approach)
  • Tor already encrypts traffic with classical methods
  • Post-quantum key exchange between peers
  • (Feature for later) A post-quantum public key must be shared between peers on first connect and saved. Use this to send tokens and verify signatures
• Storage (chat messages, peer info, etc.)
  • Evaluate which method of data storage is most suitable (diesel with sqlite and potentially other backends later)
  • A message handler that passes messages to the data storage as well as all currently connected clients
  • Actually store the messages
• Client (web based)
  • Local webapp UI
  • A local WebSocket server which your browser can connect to
  • Password authentication using OPAQUE
  • (TODO client features)