[Lightning-dev] Direct Message draft

[Rusty Russell]

René Pickhardt <r.pickhardt at googlemail.com> writes:
> Hey Rusty,
>
> I was very delighted to read your proposal. But I don't see how you prevent
> message spam. If I understand you correctly you suggest that I can
> communicate to any node along a path of peer connections (not necessarily
> backed by payment channels but kind of only known through channel
> announcements of gossip) via onions and these onions which are send within
> a new gossip message are not bound to any fees or payments.

It doesn't handle spam, but OTOH it's far cheaper than the HTLC system
(which also doesn't handle spam).  I'd be delighted to add an up-front
1msat payment, as soon as we can figure out how to do that.

The non-persistent storage costs for remembering how to forward the
reply are the 200 bytes in my implementation (one pointer to the source
peer, two SHA256s, and the shared secret).

> Let's assume I just missed some spam prevention mechanism or that we can
> fix them. Do I understand the impact of your suggestion correctly that I
> could use this protocol to
>
> 1.) create a fee free rebalancing protocol? Because I could also attach a
> new lightning message inside the onions that would allow nodes without
> direct peer connection to set up a circular rebalancing path.
> 2.) have the ability to communicate with nodes further away than just my
> peers - for example to exchange information for pathfinding and / or
> autopilots?

Indeed.  I haven't prevented it, precisely because we *can't*.  This
proposal merely gives a more efficient method than encoding via HTLCs.

Cheers,
Rusty.