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Date: Mon, 10 Aug 2015 23:01:05 +0200
Message-ID: <CAPg+sBjRFTZxOOg8ZUhTVqbZDJusZ4xyooRh1LcvwbBDSLu1oA@mail.gmail.com>
From: Pieter Wuille <pieter.wuille@gmail.com>
To: Sergio Demian Lerner <sergio.d.lerner@gmail.com>
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Cc: Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] If you had a single chance to double the
 transactions/second Bitcoin allows...
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On Aug 7, 2015 11:19 PM, "Sergio Demian Lerner via bitcoin-dev" <
bitcoin-dev@lists.linuxfoundation.org> wrote:
> b. Reduce the block rate to a half (average 5 minute blocks)
>
> Suppose this is a one time hard fork. There no drastic technical problems
with any of them: "SPV" mining and the relay network has shown that block
propagation is not an issue for such as small change. Mining centralization
won't radically change for a 2x adjustment.

I don't understand this. All problems that result from propagation delay
are literally doubled by doing so. Centralization pressure results from the
ratio between propagation time and interblock time. Efficient propagation
algorithms like the relay network make this presumably grow sublinear with
larger blocks, but changing the interblock time affects it exactly
proportionally.

All problems that result from propagation delay are literally doubled by
doing this. Doubling the block size has a smaller effect. You may argue
that these centralization effects are small, but reducing the interblock
time has a stronger effect on them than the block size.

Also, you seem to consider SPV mining a good thing? It requires trust
between miners that know eachother, and fundamentally breaks the security
assumption of SPV clients... and if the propagation/interblock ratio was
lower, SPV mining would have less effect. I'd say it is exactly a result of
the centralization pressure we're trying to avoid.

-- 
Pieter

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<p dir=3D"ltr">On Aug 7, 2015 11:19 PM, &quot;Sergio Demian Lerner via bitc=
oin-dev&quot; &lt;<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org">=
bitcoin-dev@lists.linuxfoundation.org</a>&gt; wrote:<br>
&gt; b. Reduce the block rate to a half (average 5 minute blocks)<br>
&gt;<br>
&gt; Suppose this is a one time hard fork. There no drastic technical probl=
ems with any of them: &quot;SPV&quot; mining and the relay network has show=
n that block propagation is not an issue for such as small change. Mining c=
entralization won&#39;t radically change for a 2x adjustment.=C2=A0</p>
<p dir=3D"ltr">I don&#39;t understand this. All problems that result from p=
ropagation delay are literally doubled by doing so. Centralization pressure=
 results from the ratio between propagation time and interblock time. Effic=
ient propagation algorithms like the relay network make this presumably gro=
w sublinear with larger blocks, but changing the interblock time affects it=
 exactly proportionally.</p>
<p dir=3D"ltr">All problems that result from propagation delay are literall=
y doubled by doing this. Doubling the block size has a smaller effect. You =
may argue that these centralization effects are small, but reducing the int=
erblock time has a stronger effect on them than the block size.</p>
<p dir=3D"ltr">Also, you seem to consider SPV mining a good thing? It requi=
res trust between miners that know eachother, and fundamentally breaks the =
security assumption of SPV clients... and if the propagation/interblock rat=
io was lower, SPV mining would have less effect. I&#39;d say it is exactly =
a result of the centralization pressure we&#39;re trying to avoid.</p>
<p dir=3D"ltr">-- <br>
Pieter<br>
</p>

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