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From: "Russell O'Connor" <roconnor@blockstream.io>
To: Peter Todd <pete@petertodd.org>
Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Revisiting BIP 125 RBF policy.
Date: Mon, 12 Feb 2018 18:46:43 -0500	[thread overview]
Message-ID: <CAMZUoK=BSOpUsJ=3n1jgHEAEq2M-4rigGML3Z7WN0eTgXsPp7g@mail.gmail.com> (raw)
In-Reply-To: <20180212234225.GA9131@fedora-23-dvm>

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On Mon, Feb 12, 2018 at 6:42 PM, Peter Todd <pete@petertodd.org> wrote:

> On Mon, Feb 12, 2018 at 06:19:40PM -0500, Russell O'Connor wrote:
> > On Mon, Feb 12, 2018 at 5:58 PM, Peter Todd <pete@petertodd.org> wrote:
> >
> > >
> > > I don't actually see where the problem is here. First of all, suppose
> we
> > > have a
> > > transaction T_a that already pays Alice with a feerate sufficiently
> high
> > > that
> > > we expect it to get mined in the near future. If we want to pay Bob, we
> > > can do
> > > that by simply creating a double-spend of T_a that pays both Bob and
> Alice,
> > > T_{ab}. BIP125 only requires that double-spend to have an absolute fee
> > > higher
> > > than the minimum relay feerate * size of the transaction.
> > >
> >
> > The problem is that rule 3 of BIP 125 requires you pay a fee that is
> higher
> > than the the fee of T_a *plus* the fee of the sweep-transaction that the
> > Alice has added as a unconfirmed child transaction to T_a because
> > double-spending to pay Alice and Bob invalidates Alice's
> > sweep-transaction.  Alice's sweep-transaction is very large, and hence
> pays
> > a large absolute fee even though her fee-rate is very low.  We do not
> have
> > any control over its value, hence Alice has "pinned" our RBF transaction.
>
> Ah ok, I misunderstood and didn't realise you were talking about the case
> where
> Alice re-spends her unconfirmed payment. Unfortunately I don't think that
> case
> is possible to solve without putting some kind of restriction on spending
> unconfirmed outputs; with a restriction it's fairly simple to solve.
>

Adding such a restriction was Rhavar's original suggestion in
https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-July/014688.html,
but it seems the proposal wasn't well received because it kinda destroys
CPFP.

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  reply	other threads:[~2018-02-12 23:47 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-12 15:52 [bitcoin-dev] Revisiting BIP 125 RBF policy Russell O'Connor
2018-02-12 17:30 ` rhavar
2018-02-12 22:58 ` Peter Todd
2018-02-12 23:19   ` Russell O'Connor
2018-02-12 23:42     ` Peter Todd
2018-02-12 23:46       ` Russell O'Connor [this message]
2018-02-14 14:08       ` Russell O'Connor
2018-02-14 14:16         ` Greg Sanders
2018-02-27 16:25       ` Russell O'Connor
2018-03-01 15:11         ` Peter Todd
2018-03-08 15:39           ` Russell O'Connor
2018-03-08 18:34             ` Peter Todd
2018-03-08 20:07               ` Russell O'Connor
2018-03-09 18:28                 ` Peter Todd
2018-03-09 18:40                   ` rhavar
2018-02-12 23:23   ` rhavar
2018-02-13 18:40     ` Peter Todd
2018-02-14  2:07       ` rhavar

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