docs: added simple protocol description (#83)

README.md

@@ -20,8 +20,6 @@ Decentralized. Poker planning. In terminal.
 - We use [Waku](https://waku.org) for decantralized players communication
 - Messages are end-to-end encrypted, the key is shared elsewhere as part of the room id
 
-[//]: # (# Get it)
-
 # Build it your own
  ```shell
  git clone https://github.io/six78/2-story-points-cli
@@ -37,3 +35,7 @@ make run
 ```
 
 Now share your room id with friends and start estimating your issues!
+
+# Protocol
+
+Description of the protocol can be found [here](docs/PROTOCOL.md).

docs/PROTOCOL.md

@@ -0,0 +1,67 @@
+# Protocol overview
+
+> [!NOTE]  
+> Current version is a proof of concept. It has some obvious limitations and drawbacks.
+
+Version 1 was implemented in such way for the simplicity sake of the first version.
+The goal was to make a simple solution first and then address the issues in Version 2.
+
+## Encryption
+
+All messages in the room are encrypted with a single symmetric key. There's no other encryption or signing.
+
+This prevents other users in the network to read your room's messages.
+Yet this also means that any message can be decrypted by any player in the room. This includes the votes.
+
+## Traffic
+
+We're simulating centralized environment over decentralized transport.
+Dealer acts as a server. Players only send messages to the Dealer, while Dealer publishes any changes in the room with to players.
+
+All messages are encoded as JSON (instead of protobuf) for easier changes introduction.
+
+There are a few message types defined.
+
+### `State`
+
+This is the core message of the protocol. It contains all information about current vote:
+- Players list
+- Issues list (with votes for each issue)
+- Active issue
+- Deck
+- Room state (show if votes are already revealed or not)
+
+`State` is only distributed by dealer. Moreover, this is the only message that is processed by other players. All other messages are ignored (although current encryption allows to read any message).
+
+Dealer publishes a new `State` message on any changes in the state of the room (new player, someone's vote, adding issue).
+
+### `PlayerVote`
+
+Sent by any player to vote for current issue. Contains `IssueID` and `VoteValue`.
+
+### `PlayerOnline`
+
+Sent by all players periodically to show the dealer that players are online.
+
+### `PlayerOffline`
+
+Sent by any player when leaving room or closing the app to show that the user is offline.
+
+# A note on version 2
+
+Version 2 will address the main drawbacks of version 1.
+
+1. Minimize pseudo-decentralization over dealer  
+E.g. Online/Offline messages should not spawn a new `State` message, but be processed by all players.
+
+2. Lower network load
+Encode messages in protobuf instead of JSON.
+
+3. Allow players to verify vote of a player
+Introduce votes signatures.
+
+4. Only send modified parts of `State`
+E.g. don't duplicate players list if it did not change. 
+
+The ideas about protocol v2 can be tracked and posted here: 
+- https://github.com/six78/2-story-points-cli/issues/82