[Lightning-dev] In-protocol liquidity probing and channel jamming mitigation

Joost Jager joost.jager at gmail.com
Thu Oct 21 12:55:30 UTC 2021


On Thu, Oct 21, 2021 at 12:00 PM ZmnSCPxj <ZmnSCPxj at protonmail.com> wrote:

> Good morning Joost,
>
> > A potential downside of a dedicated probe message is that it could be
> used for free messaging on lightning by including additional data in the
> payload for the recipient. Free messaging is already possible today via
> htlcs, but a probe message would lower the cost to do so because the sender
> doesn't need to lock up liquidity for it. This probably increases the spam
> potential. I am wondering if it is possible to design the probe message so
> that it is useless for anything other than probing. I guess it is hard
> because it would still have that obfuscated 1300 bytes block with the
> remaining part of the route in it and nodes can't see whether there is
> other meaningful data at the end.
>
> For the probe, the onion max size does not *need* to be 1300, we could
> reduce the size to make it less useable for *remote* messaging.
>

Yes, maybe it can be reduced a bit. But if we want to support 27 hops like
we do for payments, there will be quite some space left for messaging on
real routes which are mostly much shorter.

Joost
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