Allow public gateway providers to communicate with end users

[gnarea]

Executive summary

A public gateway provider like Relaycorp may need to contact all or some users. For example, if the provider is changing the T&Cs, they'll want to tell all users about it. Or if law enforcement has requested information on a private gateway, we'll want to notify the user of that private gateway.

Potential solutions

Option A: Augment the Gateway Synchronisation Protocol (e.g., PoWeb)

To support one-way messages from the public gateway to the private gateway.

Option B: Implement a new Relaynet Service Protocol for the communication between a private gateway and its public gateway

Requiring each gateway have an internal endpoint which is solely used to communicate with its peer. That way:

• The broadcasting case could leverage Draft Service Message Broadcast protocol #43.
• The unicast case would simply allow the public gateway to post messages to the private gateway. Alternatively, this could be offloaded to Letro.

Option C: Keep it outside the protocol suite

And just let the private gateway issue a bearer token to allow the user to use other means (e.g., Letro, email) to communicate with the public gateway provider.