From: Peter Todd <pete@petertodd•org>
To: Gloria Zhao <gloriajzhao@gmail•com>
Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] V3 Transactions are still vulnerable to significant tx pinning griefing attacks
Date: Wed, 20 Dec 2023 19:48:59 +0000 [thread overview]
Message-ID: <ZYNFK5V5e9PnT9eL@petertodd.org> (raw)
In-Reply-To: <CAFXO6=KS05So_5FizLJxCLEPwBxNPV9Wrgi=9sjzmrZ+PLpLOQ@mail.gmail.com>
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On Wed, Dec 20, 2023 at 07:13:22PM +0000, Gloria Zhao wrote:
> The "damage" of the pin can quantified by the extra fees Alice has to pay.
>
> For a v3 transaction, Mallory can attach 1000vB at 80sat/vB. This can
> increase the cost of replacement to 80,000sat.
> For a non-v3 transaction, Mallory can attach (101KvB - N) before maxing out
> the descendant limit.
> Rule #4 is pretty negligible here, but since you've already specified
> Alice's child as 152vB, she'll need to pay Rule #3 + 152sats for a
> replacement.
>
> Let's say N is 1000vB. AFAIK commitment transactions aren't usually smaller
> than this:
You make a good point that the commitment transaction also needs to be included
in my calculations. But you are incorrect about the size of them.
With taproot and ephemeral anchors, a typical commitment transaction would have
a single-sig input (musig), two taproot outputs, and an ephemeral anchor
output. Such a transaction is only 162vB, much less than 1000vB.
In my experience, only a minority of commitment transactions that get mined
have HTLCs outstanding; even if there is an HTLC outstanding, that only gets us
up to 206vB.
> > Mallory can improve the efficiency of his griefing attack by attacking
> multiple
> > targets at once. Assuming Mallory uses 1 taproot input and 1 taproot
> output for
> > his own funds, he can spend 21 ephemeral anchors in a single 1000vB
> > transaction.
>
> Note that v3 does not allow more than 1 unconfirmed parent per tx.
Ah, pity, I had misremembered that restriction as being removed, as that is a
potentially significant improvement in scenarios where you need to do things
like deal with a bunch of force closes at once.
--
https://petertodd.org 'peter'[:-1]@petertodd.org
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next prev parent reply other threads:[~2023-12-20 19:49 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-20 17:14 Peter Todd
2023-12-20 19:13 ` Gloria Zhao
2023-12-20 19:48 ` Peter Todd [this message]
2023-12-20 20:16 ` Greg Sanders
2023-12-20 21:11 ` Peter Todd
2024-01-02 11:12 ` Gloria Zhao
2024-01-02 23:18 ` Peter Todd
2024-01-02 23:43 ` Peter Todd
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