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From: ZmnSCPxj <ZmnSCPxj@protonmail.com>
To: Bastien TEINTURIER <bastien@acinq.fr>
Cc: Bitcoin Protocol Discussion
	<bitcoin-dev@lists.linuxfoundation.org>,
	"lightning-dev\\\\\\\\@lists.linuxfoundation.org"
	<lightning-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Batch exchange withdrawal to lightning requires covenants
Date: Tue, 17 Oct 2023 17:04:06 +0000	[thread overview]
Message-ID: <Ckp3N2cHGyyFyTp8IkjqYwnXsef1KxzhFs9vHQvFCpdWKUCrCfpxLBAgIXsKEtTNQqvfdyywt7weJd2pVz8UKn6egfRy46-xd17pnltcQyU=@protonmail.com> (raw)
In-Reply-To: <CACdvm3MuKmzQ1EFMJDc0ahhrG6xpD6Rr9Vh=ZTpVHa12ZALB0w@mail.gmail.com>

Good morning Bastien,

I have not gotten around to posting it yet, but I have a write-up in my computer with the title:

> Batched Splicing Considered Risky

The core of the risk is that if:

* I have no funds right now in a channel (e.g. the LSP allowed me to have 0 reserve, or this is a newly-singlefunded channel from the LSP to me).
* I have an old state (e.g. for a newly-singlefunded channel, it could have been `update_fee`d, so that the initial transaction is old state).

Then if I participate in a batched splice, I can disrupt the batched splice by broadcasting the old state and somehow convincing miners to confirm it before the batched splice.

Thus, it is important for *any* batched splicing mechanism to have a backout, where if the batched splice transaction can no longer be confirmed due to some participant disrupting it by posting an old commitment transaction, either a subset of the splice is re-created or the channels revert back to pre-splice state (with knowledge that the post-splice state can no longer be confirmed).

I know that current splicing tech is to run both the pre-splice and post-splice state simultaneously until the splicing transaction is confirmed.
However we need to *also* check if the splicing transaction *cannot* be confirmed --- by checking if the other inputs to the splice transaction were already consumed by transactions that have deeply confirmed, and in that case, to drop the post-splice state and revert to the pre-splice state.
I do not know if existing splice implementations actually perform such a check.
Unless all splice implementations do this, then any kind of batched splicing is risky.

Regards,
ZmnSCPxj



  reply	other threads:[~2023-10-17 17:04 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-10-17 13:03 [bitcoin-dev] Batch exchange withdrawal to lightning requires covenants Bastien TEINTURIER
2023-10-17 17:04 ` ZmnSCPxj [this message]
2023-10-17 17:10   ` Greg Sanders
2023-10-17 17:17     ` ZmnSCPxj
2023-10-17 19:10 ` [bitcoin-dev] [Lightning-dev] " Antoine Riard
2023-10-18 14:35   ` Bastien TEINTURIER
2023-10-18 18:03     ` Antoine Riard
2023-10-19  7:35       ` Bastien TEINTURIER
2023-10-19 17:09         ` Antoine Riard

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