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References: <20151220132842.GA25481@muck>
	<ema8a70574-c28e-4c43-a1e3-5f2f4df7d3a2@platinum>
Date: Sat, 26 Dec 2015 16:09:18 +0000
Message-ID: <CAE-z3OUrCFkVQ+1th-BjkZf1YEhPjub7TA_2J-CRNmCs6Bb7Dg@mail.gmail.com>
From: Tier Nolan <tier.nolan@gmail.com>
To: Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>
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Subject: Re: [bitcoin-dev] We need to fix the block withholding attack
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On Sat, Dec 26, 2015 at 8:23 AM, Eric Lombrozo via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> Unfortunately, this also means longer confirmation times, lower
> throughput, and lower miner revenue. Note, however, that confirmations
> would (on average) represent more PoW, so fewer confirmations would be
> required to achieve the same level of security.
>


No, the re-target compensates so that the number of blocks in the last two
weeks is 2016.  If a soft fork forces miners to throw away 25% of their
blocks, then the difficulty will drop by 75% to keep things balanced.
Throwing away 75% of blocks has the same effect on difficulty as destroying
75% of mining hardware.

The block interval will only increase until the next re-target.

Slowly increasing the fraction of blocks which are thrown away gives the
re-target algorithm time to adjust, so it is another advantage.

If the rule was instantly changed so that 95% of blocks were thrown away,
then there could be up to 40 weeks until the next retarget and that would
give 200 minute block times until the adjustment.

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<div dir=3D"ltr"><br><div class=3D"gmail_extra"><br><div class=3D"gmail_quo=
te">On Sat, Dec 26, 2015 at 8:23 AM, Eric Lombrozo via bitcoin-dev <span di=
r=3D"ltr">&lt;<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" targ=
et=3D"_blank">bitcoin-dev@lists.linuxfoundation.org</a>&gt;</span> wrote:<b=
r><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:=
1px #ccc solid;padding-left:1ex">


<div><span class=3D""></span><div><span><div>
<div>Unfortunately, this also means longer confirmation times, lower throug=
hput, and lower miner revenue. Note, however, that confirmations would (on =
average) represent more PoW, so fewer confirmations would be required to ac=
hieve the same level of security.</div>
</div></span></div></div></blockquote><div><br><br></div><div>No, the re-ta=
rget compensates so that the number of blocks in the last two weeks is 2016=
.=C2=A0 If a soft fork forces miners to throw away 25% of their blocks, the=
n the difficulty will drop by 75% to keep things balanced.=C2=A0 Throwing a=
way 75% of blocks has the same effect on difficulty as destroying 75% of mi=
ning hardware.<br><br></div><div>The block interval will only increase unti=
l the next re-target.<br><br>Slowly increasing the fraction of blocks which=
 are thrown away gives the re-target algorithm time to adjust, so it is ano=
ther advantage.=C2=A0 <br><br>If the rule was instantly changed so that 95%=
 of blocks were thrown away, then there could be up to 40 weeks until the n=
ext retarget and that would give 200 minute block times until the adjustmen=
t.<br></div></div></div></div>

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