Date: Mon, 22 Jun 2020 08:15:37 +0000
To: Bastien TEINTURIER <bastien@acinq.fr>
From: ZmnSCPxj <ZmnSCPxj@protonmail.com>
Reply-To: ZmnSCPxj <ZmnSCPxj@protonmail.com>
Message-ID: <F7ZA7-s3UnfMlhYdA1esEhJIhgNIBSKCfHWG64UAcMvQM-ZS6Do7xMg8OfYhbkHIFNodbLIe51TQG7Ps3jFXFoS80EJ6oEh8n2009vbnl04=@protonmail.com>
In-Reply-To: <CACdvm3NTY1UYWJg=SJm+TAZSi5RophxhRvze9gKi9PyEHx0PgA@mail.gmail.com>
References: <PtYNeePySy_thDHm8FwIIGEk32EjJpSmiwPctyEg0hOrLZEHjO1IBghm4MWY88g51K-XF2pf_JDnW0UdTL6QSbACEj21h9U1s5ITc_N3I6Q=@protonmail.com>
 <67334082-5ABA-45C7-9C09-FF19B119C80D@mattcorallo.com>
 <62P_3wvv8z7AVCdKPfh-bs30-LliHkx9GI9Og3wqIK6hadIG0d6MJJm077zac1erpPUy31FqgZjkAjEl9AQtrOCg4XA5cxozBb7-OIbbgvE=@protonmail.com>
 <4c4f3a06-0078-ef6a-7b06-7484f0f9edf1@mattcorallo.com>
 <CACdvm3Of_9zhNmzCxeK-z8oz6wU=8RuDjr0R9+yrGeFjLYz9pg@mail.gmail.com>
 <20200619195846.fclw4ilngvbbf2kk@ganymede>
 <20200619205220.fshbr7pbijaerbf2@ganymede>
 <CACdvm3O+A5M17rqejzAMUzE+fxLdzqnDY2m5+rnc5C=nzyPp9g@mail.gmail.com>
 <20200620103647.g62srlcxbjqpaqj6@ganymede>
 <CACdvm3NTY1UYWJg=SJm+TAZSi5RophxhRvze9gKi9PyEHx0PgA@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>,
 lightning-dev <lightning-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] [Lightning-dev] RBF Pinning with Counterparties
	and Competing Interest
Precedence: list

Good morning Bastien,

> Thanks for the detailed write-up on how it affects incentives and central=
ization,
> these are good points. I need to spend more time thinking about them.
>
> > This is one reason I suggested using independent pay-to-preimage
> > transactions[1]
>
> While this works as a technical solution, I think it has some incentives =
issues too.
> In this attack, I believe the miners that hide the preimage tx in their m=
empool have
> to be accomplice with the attacker, otherwise they would share that tx wi=
th some of
> their peers, and some non-miner nodes would get that preimage tx and be a=
ble to
> gossip them off-chain (and even relay them to other mempools).

I believe this is technically possible with current mempool rules, without =
miners cooperating with the attacker.

Basically, the attacker releases two transactions with near-equal fees, so =
that neither can RBF the other.
It releases the preimage tx near miners, and the timelock tx near non-miner=
s.

Nodes at the boundaries between those that receive the preimage tx and the =
timelock tx will receive both.
However, they will receive one or the other first.
Which one they receive first will be what they keep, and they will reject t=
he other (and *not* propagate the other), because the difference in fees is=
 not enough to get past the RBF rules (which requires not just a feerate in=
crease, but also an increase in absolute fee, of at least the minimum relay=
 feerate times transaction size).

Because they reject the other tx, they do not propagate the other tx, so th=
e boundary between the two txes is inviolate, neither can get past that bou=
ndary, this occurs even if everyone is running 100% unmodified Bitcoin Core=
 code.

I am not a mempool expert and my understanding may be incorrect.

Regards,
ZmnSCPxj