From ZmnSCPxj at protonmail.com  Thu Oct 21 10:00:05 2021
From: ZmnSCPxj at protonmail.com (ZmnSCPxj)
Date: Thu, 21 Oct 2021 10:00:05 +0000
Subject: [Lightning-dev] In-protocol liquidity probing and channel
	jamming mitigation
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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.

Regards,
ZmnSCPxj