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Date: Mon, 17 Aug 2015 17:44:56 -0400
Message-ID: <CAB+qUq79BgiTGFS1yLxxogg8907jCUtNDmBhnikLWc1fqofNyg@mail.gmail.com>
From: Chris Pacia <ctpacia@gmail.com>
To: Peter Todd <pete@petertodd.org>
Content-Type: multipart/alternative; boundary=001a113ed538657335051d88b699
Cc: bitcoin-dev@lists.linuxfoundation.org
Subject: Re: [bitcoin-dev] Incentives to run full nodes
Precedence: list

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On Aug 17, 2015 5:29 PM, "Peter Todd via bitcoin-dev" <
bitcoin-dev@lists.linuxfoundation.org> wrote:
From the point of view of a
> wallet, it's not very secure to use Hearn-style SPV mode, and volunteers
> running full nodes doesn't help things. Sybil attacking the IP address
> space is pretty easy in comparison to aquiring hashing power sufficient
> to create false confirmations, so any attacker able to do the former
> will likely be running the full node you're connecting too anyway.
> Ultimately, Hearn-style SPV is a close approximation to just trusting
> anyone with a non-trivial amount of hashing power. (and getting that is
> surprisingly easy, e.g. w/ SPV mining)

Can you explain how the spv node fails against an attacker with a
non-trivial amount of hash power where a full node doesn't? To attack an
spv wallet that is waiting for 6 or 10 confirmations, you would not only
need to Sybil them but also summon a massive amount of hashing power to
create a chain of headers (while forgoing the opportunity to mine valid
blocks with that hash power).

But could someone with that much hash power not Sybil a full node and give
them a chain for valid blocks (but on an orphan fork)? The failure model
doesn't seem specific to spv to me.

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<p dir=3D"ltr"><br>
On Aug 17, 2015 5:29 PM, &quot;Peter Todd via bitcoin-dev&quot; &lt;<a href=
=3D"mailto:bitcoin-dev@lists.linuxfoundation.org">bitcoin-dev@lists.linuxfo=
undation.org</a>&gt; wrote:<br>
 From the point of view of a<br>
&gt; wallet, it&#39;s not very secure to use Hearn-style SPV mode, and volu=
nteers<br>
&gt; running full nodes doesn&#39;t help things. Sybil attacking the IP add=
ress<br>
&gt; space is pretty easy in comparison to aquiring hashing power sufficien=
t<br>
&gt; to create false confirmations, so any attacker able to do the former<b=
r>
&gt; will likely be running the full node you&#39;re connecting too anyway.=
<br>
&gt; Ultimately, Hearn-style SPV is a close approximation to just trusting<=
br>
&gt; anyone with a non-trivial amount of hashing power. (and getting that i=
s<br>
&gt; surprisingly easy, e.g. w/ SPV mining)</p>
<p dir=3D"ltr">Can you explain how the spv node fails against an attacker w=
ith a non-trivial amount of hash power where a full node doesn&#39;t? To at=
tack an spv wallet that is waiting for 6 or 10 confirmations, you would not=
 only need to Sybil them but also summon a massive amount of hashing power =
to create a chain of headers (while forgoing the opportunity to mine valid =
blocks with that hash power). </p>
<p dir=3D"ltr">But could someone with that much hash power not Sybil a full=
 node and give them a chain for valid blocks (but on an orphan fork)? The f=
ailure model doesn&#39;t seem specific to spv to me. </p>

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