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From: Eric Voskuil <eric@voskuil.org>
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Date: Sun, 23 Aug 2020 10:49:35 -0700
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References: <afcedaf1-dd69-9402-eeeb-006bb9211b98@mattcorallo.com>
In-Reply-To: <afcedaf1-dd69-9402-eeeb-006bb9211b98@mattcorallo.com>
To: Matt Corallo <lf-lists@mattcorallo.com>
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Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Generalizing feature negotiation when new p2p
connections are setup
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X-List-Received-Date: Sun, 23 Aug 2020 17:49:38 -0000
> On Aug 21, 2020, at 15:16, Matt Corallo <lf-lists@mattcorallo.com> wrote:
>=20
> =EF=BB=BFHmm, could that not be accomplished by simply building this into n=
ew messages? eg, send "betterprotocol", if you see a verack and no "betterpr=
otocol" from your peer, send "worseprotocol" before you send a "verack".
>=20
> Matt
>=20
>> On 8/21/20 5:17 PM, Jeremy wrote:
>> As for an example of where you'd want multi-round, you could imagine a sc=
enario where you have a feature A which gets bugfixed by the introduction of=
feature B, and you don't want to expose that you support A unless you first=
negotiate B. Or if you can negotiate B you should never expose A, but for o=
ld nodes you'll still do it if B is unknown to them.
This seems to imply a security benefit (I can=E2=80=99t discern any other ra=
tionale for this complexity). It should be clear that this is no more than t=
rivially weak obfuscation and not worth complicating the protocol to achieve=
.
>> An example of this would be (were it not already out without a feature ne=
gotiation existing) WTXID/TXID relay.
>> The SYNC primitve simply codifies what order messages should be in and wh=
en you're done for a phase of negotiation offering something. It can be done=
without, but then you have to be more careful to broadcast in the correct o=
rder and it's not clear when/if you should wait for more time before respond=
ing.
>> On Fri, Aug 21, 2020 at 2:08 PM Jeremy <jlrubin@mit.edu <mailto:jlrubin@m=
it.edu>> wrote:
>> Actually we already have service bits (which are sadly limited) which a=
llow negotiation of non bilateral feature
>> support, so this would supercede that.
>> --
>> @JeremyRubin <https://twitter.com/JeremyRubin><https://twitter.com/Jer=
emyRubin>
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