Feedback-ID: i525146e8:Fastmail
Date: Thu, 20 Oct 2022 00:05:33 -0400
From: Peter Todd <pete@petertodd.org>
To: Sergej Kotliar <sergej@bitrefill.com>,
 Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Message-ID: <Y1DJDR/28XhUbirX@petertodd.org>
References: <CABZBVTC5kh7ca3KhVkFPdQjnsPhP4Kun1k3K6cPkarrjUiTJpA@mail.gmail.com>
 <CABZBVTCgiQFtxEyeOU=-SGDQUDthyy7sOgPwiT+OVi35LVivyA@mail.gmail.com>
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In-Reply-To: <CABZBVTCgiQFtxEyeOU=-SGDQUDthyy7sOgPwiT+OVi35LVivyA@mail.gmail.com>
Subject: Re: [bitcoin-dev] [Opt-in full-RBF] Zero-conf apps in immediate
 danger
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On Wed, Oct 19, 2022 at 04:29:57PM +0200, Sergej Kotliar via bitcoin-dev wr=
ote:
> Hi all,
>=20
> Chiming in on this thread as I feel like the real dangers of RBF as defau=
lt
> policy aren't sufficiently elaborated here. It's not only about the
> zero-conf (I'll get to that) but there is an even bigger danger called the
> american call option, which risks endangering the entirety of BIP21 "Scan
> this QR code with your wallet to buy this product" model that I believe
> we've all come to appreciate. Specifically, in a scenario with high
> volatility and many transactions in the mempools (which is where RBF would
> come in handy), a user can make a low-fee transaction and then wait for
> hours, days or even longer, and see whether BTCUSD moves. If BTCUSD moves
> up, user can cancel his transaction and make a new - cheaper one. The

I just checked this, and Bitrefill accepts transactions with RBF enabled.

> biggest risk in accepting bitcoin payments is in fact not zeroconf risk
> (it's actually quite easily managed), it's FX risk as the merchant must
> commit to a certain BTCUSD rate ahead of time for a purchase. Over time
> some transactions lose money to FX and others earn money - that evens out
> in the end. But if there is an _easily accessible in the wallet_ feature =
to
> "cancel transaction" that means it will eventually get systematically

=2E..and I checked this with Electrum on Android, which has a handy "Cancel
Transaction" feature in the UI to easily cancel a payment. Which I did. You
should have a pending payment from this email, and unsurprisingly I don't h=
ave
my gift card. :)

The ship has already sailed on this. I'd suggest accepting Lightning, which
drastically shortens the time window involved.

FWIW, fixedfloat.com already deals with this call option risk by charging a
higher fee (1% vs 0.5%) for conversions where the exact destination amount =
has
been locked in; the default is for the exact destination amount to be picke=
d at
the moment of confirmation.

> abused. A risk of X% loss on many payments that's easy to systematically
> Bitrefill currently processes 1500-2000 onchain payments every day. For u=
s,
> a world where bitcoin becomes de facto RBF by default, means that we would

Electrum is RBF by default. So does Green Wallet, and many other wallets,  =
as
well as many exchanges. Most of those wallets/exchanges don't even have a w=
ay
to send a transaction without RBF. This ship has sailed.

--=20
https://petertodd.org 'peter'[:-1]@petertodd.org

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