protocol.md

# The Authentication and Message Exchange Protocol

[A]lice wants to communicate with [B]ob privately.

## Protocol Steps

1. Authenticate to the server and establish communication.
   1. A tells the server to open a communication.
      2. A sends an id_code to the server.
      3. A gets a comm_id from the server.
   2. B tells the server to answer A's communication request.
      1. B receives A's challenge.
      2. B answers the solution to the server.
      3. The server checks the solution and accepts the communication establishment.
2. Generate and exchange an ephemeral key.
3. Instantiate symmetric encryption using the ephemeral key.
4. Authenticate each other directly.
5. (?) Check communication transcript (avoid malicious server).