cmp.md

I'm not well versed with Matrix, so please let me know where I've erred.

My understanding is that Matrix is a federated chat protocol, using both server-to-server and server-to-client connections for moving messages around. As I understand it, chat data can be cached on clients, but fundamentally lives on the servers, which host anywhere between 1 and maybe 1000s of users.

Cabal is peer-to-peer, in the sense that there is no server/client distinction. Any peer currently has a full copy of chat history, and seeks out other peers in the cabal to send and receive new messages to. This means that nobody has to choose a server to join / entrust their identity to: it lives on your computer as your private/public keypair. Cabal is really just a database that anybody with the shared key can append new data to. Peers sync any new data around until everyone has the same eventual state. The clients (cabal-desktop, etc) scan everyone's append-only feed of messages to build a view of chat history for each channel.

There are some practical effects that arise from this approach:

1. no servers are required for coordination or ownership: everything you need to create/join a cabal is on your laptop/phone
2. servers, if used, strengthen the network, but are an equal peer & don't have the power to terminate/control anyone's identity (they're just dumb pipes that are online 24/7)
3. because the full database is on every machine, using the app in offline or low connectivity or local-network-only environments works the same way as when you're on the internet: it's just reading and writing to a database!

Hello! I'm the one who had asked on Twitter.

I think this is a good start and a very clear, yet succinct summary, thank you for this.

What I think would be interesting next is to consider this difference from a user's point of view. I'm going to ask a few questions that come to mind as examples, feel free to ignore:

• What does this architecture bring to me in terms of security and privacy (vs a centralized or federated system)?
• How much privacy does Cabal allow? For example:
  • Is there plausible deniability
  • Is the protocol obfuscating my identity and location more, less, or comparably to other technologies (and Matrix in particular)?
• Matrix has the option of encrypted rooms, does Cabal offer that too?
• What is "eventual consistency" and how does it affect me? In particular, as a user, am I guaranteed of reading messages in the same order as everyone else?
• Is there history for a "room"? Does it disappear if all pears disconnect/trash their cache?
• How does peer discovery work
• How do I make sure who I'm talking to is who they say they are?