From: "David A. Harding" <dave@dtrt•org>
To: Jeremy <jlrubin@mit•edu>,
Bitcoin Protocol Discussion
<bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] A Replacement for RBF and CPFP: Non-Destructive TXID Dependencies for Fee Sponsoring
Date: Sat, 19 Sep 2020 09:37:16 -0400 [thread overview]
Message-ID: <20200919133716.d5ofags2tprlvpqm@ganymede> (raw)
In-Reply-To: <CAD5xwhi6+Q-UX2xVnD4TE9uEbe-omQ748tpJJpYdrMNnG6D5vA@mail.gmail.com>
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On Fri, Sep 18, 2020 at 05:51:39PM -0700, Jeremy via bitcoin-dev wrote:
> I'd like to share with you a draft proposal for a mechanism to replace
> CPFP and RBF for increasing fees on transactions in the mempool that
> should be more robust against attacks.
Interesting idea! This is going to take a while to think about, but I
have one immediate question:
> To prevent garbage sponsors, we also require that:
>
> 1. The Sponsor's feerate must be greater than the Sponsored's ancestor fee rate
>
> We allow one Sponsor to replace another subject to normal replacement
> policies, they are treated as conflicts.
Is this in the reference implementation? I don't see it and I'm
confused by this text. I think it could mean either:
1. Sponsor Tx A can be replaced by Sponsor Tx B if A and B have at least
one input in common (which is part of the "normal replacement policies")
2. A can be replaced by B even if they don't have any inputs in common
as long as they do have a Sponsor Vector in common (while otherwise
using the "normal replacement policies").
In the first case, I think Mallory can prevent Bob from
sponsor-fee-bumping (sponsor-bumping?) his transaction by submitting a
sponsor before he does; since Bob has no control over Mallory's inputs,
he can't replace Mallory's sponsor tx.
In the second case, I think Mallory can use an existing pinning
technique to make it expensive for Bob to fee bump. The normal
replacement policies require a replacement to pay an absolute higher fee
than the original transaction, so Mallory can create a 100,000 vbyte
transaction with a single-vector sponsor at the end pointing to Bob's
transaction. This sponsor transaction pays the same feerate as Bob's
transaction---let's say 50 nBTC/vbyte, so 5 mBTC total fee. In order
for Bob to replace Mallory's sponsor transaction with his own sponsor
transaction, Bob needs to pay the incremental relay feerate (10
nBTC/vbyte) more, so 6 mBTC total ($66 at $11k/BTC).
Thanks,
-Dave
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next prev parent reply other threads:[~2020-09-19 13:38 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-19 0:51 Jeremy
2020-09-19 1:39 ` Cory Fields
2020-09-19 16:16 ` Jeremy
2020-09-19 13:37 ` David A. Harding [this message]
2020-09-19 15:01 ` nopara73
2020-09-19 16:30 ` Jeremy
2020-09-19 17:24 ` David A. Harding
2020-09-19 18:39 ` Antoine Riard
2020-09-19 19:13 ` Antoine Riard
2020-09-19 19:46 ` Jeremy
2020-09-20 23:10 ` Antoine Riard
2020-09-21 14:52 ` David A. Harding
2020-09-21 16:27 ` Jeremy
2020-09-21 23:40 ` Antoine Riard
2020-09-22 18:05 ` Suhas Daftuar
2020-09-23 22:10 ` Jeremy
2020-09-24 4:22 ` Dmitry Petukhov
2020-09-22 6:24 ArmchairCryptologist
2020-09-22 13:52 ` Antoine Riard
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