public inbox for bitcoindev@googlegroups.com
 help / color / mirror / Atom feed
From: "David A. Harding" <dave@dtrt.org>
To: Jeremy <jlrubin@mit.edu>
Cc: 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 13:24:17 -0400	[thread overview]
Message-ID: <20200919172417.ajlbqbmtuvk7t7be@ganymede> (raw)
In-Reply-To: <CAD5xwhjZt25Bx+0MqfuY4OLJRWYmKZrfof86pPUAfJRDDsBQWA@mail.gmail.com>

[-- Attachment #1: Type: text/plain, Size: 1267 bytes --]

On Sat, Sep 19, 2020 at 09:30:56AM -0700, Jeremy wrote:
> Yup, I was aware of this limitation but I'm not sure how practical it is as
> an attack because it's quite expensive for the attacker. 

It's cheap if:

1. You were planning to consolidate all those UTXOs at roughly that
   feerate anyway.

2. After you no longer need your pinning transaction in the mempool, you
   make an out-of-band arrangement with a pool to mine a small
   conflicting transaction.

> But there are a few simple policies that can eliminate it:
> 
> 1) A Sponsoring TX never needs to be more than, say, 2 inputs and 2
> outputs. Restricting this via policy would help, or more flexibly
> limiting the total size of a sponsoring transaction to 1000 bytes.

I think that works (as policy).

> 2) Make A Sponsoring TX not need to pay more absolute fee, just needs to
> increase the feerate (perhaps with a constant relay fee bump to prevent
> spam).

I think it'd be hard to find a constant relay fee bump amount that was
high enough to prevent abuse but low enough not to unduly hinder
legitimate users.

> I think 1) is simpler and should allow full use of the sponsor mechanism
> while preventing this class of issue mostly.

Agreed.

Thanks,

-Dave

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

  reply	other threads:[~2020-09-19 17:25 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-19  0:51 [bitcoin-dev] A Replacement for RBF and CPFP: Non-Destructive TXID Dependencies for Fee Sponsoring Jeremy
2020-09-19  1:39 ` Cory Fields
2020-09-19 16:16   ` Jeremy
2020-09-19 13:37 ` David A. Harding
2020-09-19 15:01   ` nopara73
2020-09-19 16:30   ` Jeremy
2020-09-19 17:24     ` David A. Harding [this message]
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

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=20200919172417.ajlbqbmtuvk7t7be@ganymede \
    --to=dave@dtrt.org \
    --cc=bitcoin-dev@lists.linuxfoundation.org \
    --cc=jlrubin@mit.edu \
    /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