public inbox for bitcoindev@googlegroups.com
 help / color / mirror / Atom feed
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>

[-- Attachment #1: Type: text/plain, Size: 1783 bytes --]

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

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

  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 [bitcoin-dev] V3 Transactions are still vulnerable to significant tx pinning griefing attacks 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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=ZYNFK5V5e9PnT9eL@petertodd.org \
    --to=pete@petertodd.org \
    --cc=bitcoin-dev@lists.linuxfoundation.org \
    --cc=gloriajzhao@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox