nullspace: an experimental confederal chat protocol

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Nullspace (aka "Xirtam") is a confederal end-to-end encrypted chat system. A confederal protocol shares two similarities with a federated protocol like Matrix:

• we use a server-client architecture; it's not purely p2p
• we avoid having one gigantic server and instead allow anyone to join the network with their own server.

There are two critical differences though:

• User sovereignty: end-users, not servers, control root-of-trust information like public keys, as well as routing information like which server they're currently hosted at. These two pieces of information allow a user to avoid cryptographic trust in servers and costlessly switch between servers, which is not possible in a federated system like email or Matrix.
• No server-to-server protocol: when a client needs to interact with a client hosted at a different server, it talks directly to that server. A separate server-to-server federation protocol (notoriously complex in the case of Matrix) is entirely avoided. Since the servers don't need constant interconnection to form a single network; the network is only "loosely" connected by accepting the same user-sovereign authentication scheme. (This is also the origin of the "confederal" name, since confederations are more loosely organized than federations.)

This blogpost provides some context on why confederal protocols are superior to both federated and "fully" peer-to-peer protocols, since they combine essentially all the advantages of a centralized or federated system with decentralized trust.

Design features

Some notable design features:

• SimpleX-like unidirectional mailboxes for DMs
• An very easy-to-implement wire protocol based on JSON-RPC long-polling
• Robust high-level client library that abstracts over all encryption and storage, inspired by Telegram's TDLib
• Novel end-to-end encryption protocol that avoids "ratcheting" to achieve better performance and robustness, plus a much simpler implementation. E2EE is always-on and performant, even for large groups.

Implementation progress

• Directory RPC + PoW updates + header sync (server + dirclient)
• Server RPC + mailbox storage/ACLs + device auth
• Core structs: usernames, server descriptors, certificates, message kinds
• DM encryption format
• MVP group protocol (group IDs, rekeying, membership control)
• PFPs, group names, and other quality of life features
• Advanced group features (directory naming, server migration)
• Attachments / file transfers
• 1-to-1 voice calls
• Group voice calls
• Discord-like "communities" with fine-grained ACLs, channels, etc