[Lightning-dev] Packet switching via intermediary rendezvous node

Anthony Towns aj at erisian.com.au
Fri Nov 16 15:31:59 UTC 2018

On Thu, Nov 15, 2018 at 07:24:29PM -0800, Olaoluwa Osuntokun wrote:
> > If I'm not mistaken it'll not be possible for us to have spontaneous
> > ephemeral key switches while forwarding a payment
> If this _was_ possible, then it seems that it would allow nodes to create
> unbounded path lengths (looks to other nodes as a normal packet), possibly
> by controlling multiple nodes in a route, thereby sidestepping the 20 hop
> limit all together.

If you control other nodes in the route you can trivially create a "path"
of more than 20 hops -- go 18 hops from your first node to your second
node, and have the second node trigger on the payment hash to create
an entirely new onion to go another 18 hops, repeating if necessary to
create an arbitrarily long route.

> This would be undesirable many reasons, the most dire of
> which being the ability to further amplify null-routing attacks.

That doesn't really *amplify* null-routing attacks -- even if its
circular, you're still locking additional funds up each time you
route through yourself.


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