On Sat, Oct 21, 2023 at 09:05:35PM +0100, Antoine Riard via bitcoin-dev wrote:
> In the meanwhile, lightning experts have already deployed mitigations which
> are hardening the lightning ecosystem significantly in face of simple or
> medium attacks. More advanced attacks can only be mounted if you have
> sufficient p2p and mempool knowledge as was pointed out by other bitcoin
> experts like Matt or Peter (which take years to acquire for average bitcoin
> developers) and the months of preparation to attempt them.

To be clear, I am not making any claims about how easy this attack is to pull
off. Indeed, there are probably even cases where it happens by accident. Eg
imagine a node with a HTLC-preimage that happens to be offline and then online
at the right time to broadcast a HTLC-preimage redemption transaction with a
higher fee than the timeout transaction. If the other node happens to go
offline at the right time, after broadcasting the timeout transaction, it may
not notice the HTLC-preimage in the mempool, and thus fail to redeem it.

OP_Expire would help avoid this situation, by making it impossible to redeem
the HTLC-preimage after the timeout.

-- 
https://petertodd.org 'peter'[:-1]@petertodd.org