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From: slush <slush@centrum.cz>
Date: Thu, 19 Jun 2014 22:55:48 +0200
Message-ID: <CAJna-HgP=RvbFpkdwqkoNP0fmMg6r80zDKrA-Cb2mcbmyjOTEA@mail.gmail.com>
To: Mark Friedenbach <mark@monetize.io>
Content-Type: multipart/alternative; boundary=089e013a219ccb086804fc369bf7
Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] BlockPow: A Practical Proposal to prevent
 mining pools AND reduce payoff variance:
Precedence: list

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Miner issues are just one thing what came to my mind. What about validating
transactions? How the pool can be sure that miner is running up to date
bitcoind which do full validation of transactions? Not talking that if
every miner takes his own set of transaction, pool need to calculate merkle
root for every submit, to check its correctness.

I don't think it *cannot* be done, it is just extremely hard and there's no
economic motivation for such complication on pool side. Just see current
pools, they are full of security and stability bugs even while using such
trivial protocol like Stratum...

slush

On Thu, Jun 19, 2014 at 10:39 PM, Mark Friedenbach <mark@monetize.io> wrote:

> Do you need to do full validation? There's an economic cost to mining
> invalid blocks, and even if that were acceptable there's really no
> reason to perform such an attack. The result would be similar to a block
> withholding attack, but unlike block withholding it would be trivially
> detectable if/when full validation was performed.
>
> To protect yourself and to detect incorrect mining software you could
> stochastically validate a randomly selected sample of shares, as your
> hardware requirements allow.
>
> On 06/19/2014 01:26 PM, slush wrote:
> > With GBT, simply hashing the block header is not enough, because pool
> > cannot rely on anything provided by the client. Its not only about
> > things like withdrawal attacks, but more about hidden bugs in various
> > miners. It is extremely hard to do full validation for *every* of
> > submitted shares.
>

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<div dir=3D"ltr"><div class=3D"gmail_extra">Miner issues are just one thing=
 what came to my mind. What about validating transactions? How the pool can=
 be sure that miner is running up to date bitcoind which do full validation=
 of transactions? Not talking that if every miner takes his own set of tran=
saction, pool need to calculate merkle root for every submit, to check its =
correctness.</div>

<div class=3D"gmail_extra"><br></div><div class=3D"gmail_extra">I don&#39;t=
 think it *cannot* be done, it is just extremely hard and there&#39;s no ec=
onomic motivation for such complication on pool side. Just see current pool=
s, they are full of security and stability bugs even while using such trivi=
al protocol like Stratum...</div>

<div class=3D"gmail_extra"><br></div><div class=3D"gmail_extra">slush</div>=
<div class=3D"gmail_extra"><br><div class=3D"gmail_quote">On Thu, Jun 19, 2=
014 at 10:39 PM, Mark Friedenbach <span dir=3D"ltr">&lt;<a href=3D"mailto:m=
ark@monetize.io" target=3D"_blank">mark@monetize.io</a>&gt;</span> wrote:<b=
r>

<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex">Do you need to do full validation? There&#39=
;s an economic cost to mining<br>
invalid blocks, and even if that were acceptable there&#39;s really no<br>
reason to perform such an attack. The result would be similar to a block<br=
>
withholding attack, but unlike block withholding it would be trivially<br>
detectable if/when full validation was performed.<br>
<br>
To protect yourself and to detect incorrect mining software you could<br>
stochastically validate a randomly selected sample of shares, as your<br>
hardware requirements allow.<br>
<div class=3D"HOEnZb"><div class=3D"h5"><br>
On 06/19/2014 01:26 PM, slush wrote:<br>
&gt; With GBT, simply hashing the block header is not enough, because pool<=
br>
&gt; cannot rely on anything provided by the client. Its not only about<br>
&gt; things like withdrawal attacks, but more about hidden bugs in various<=
br>
&gt; miners. It is extremely hard to do full validation for *every* of<br>
&gt; submitted shares.<br>
</div></div></blockquote></div><br></div></div>

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