Implement conversation hinting #33
Description
Problem
A conversation_id is included on the outside of every payload so that clients can identify which payloads need to be decrypted. Delivery addresses may contain messages intended for other clients, so clients need to determine if a message is of interest, and which conversation it belongs to.
Including the conversation_id obscured, leaks conversational metadata and allows observers to associate payloads together.
Requirements for a potential solution:
- messages from the same conversation SHOULD have conversation hints which are indistinguishable from random.
- Unmasking of a conversation hint, SHOULD not unmask previous messages.
- Unmasking of a conversation hint, SHOULD not unmask all future messages.