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Date: Wed, 1 Jul 2015 01:45:09 +0200
Message-ID: <CAPg+sBj2P6ZUxJyrn3Dq76USO5kDTfpkF-zuYsKQbpQbTnyq2A@mail.gmail.com>
From: Pieter Wuille <pieter.wuille@gmail.com>
To: Peter Grigor <peter@grigor.ws>
Content-Type: multipart/alternative; boundary=089e0160aa48ef41f60519c4cb76
Cc: bitcoin-dev@lists.linuxfoundation.org
Subject: Re: [bitcoin-dev] A possible solution for the block size limit:
 Detection and rejection of bloated blocks by full nodes.
Precedence: list

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The problem with this approach is that you need 100% exact behaviour for
every node on the network in their decision to reject a particular block.
So we need a 100% mempool synchronization across all nodes - otherwise just
an attempted double spend could result in a fork in the network because
some nodes saw it and some didn't. And actually, if we had 100% mempool
synchronization, we wouldn't need a blockchain in the first place, because
we could just use "first to enter mempool" as validity criterion.

On Wed, Jul 1, 2015 at 1:41 AM, Peter Grigor <peter@grigor.ws> wrote:

> The block size debate centers around one concern it seems. To wit: if
> block size is increased malicious miners may publish unreasonably large
> "bloated" blocks. The way a miner would do this is to generate a plethora
> of private, non-propagated transactions and include these in the block they
> solve.
>
> It seems to me that these bloated blocks could easily be detected by other
> miners and full nodes: they will contain a very high percentage of
> transactions that aren't found in the nodes' own memory pools. This
> signature can be exploited to allow nodes to reject these bloated blocks.
> The key here is that any malicious miner that publishes a block that is
> bloated with his own transactions would contain a ridiculous number of
> transactions that *absolutely no other full node has in its mempool*.
>
> Simply put, a threshold would be set by nodes on the allowable number of
> non-mempool transactions allowed in a solved block (say, maybe, 50% -- I
> really don't know what it should be). If a block is published which
> contains more that this threshold of non-mempool transactions then it is
> rejected.
>
> If this idea works the block size limitation could be completely removed.
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
>

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<div dir=3D"ltr">The problem with this approach is that you need 100% exact=
 behaviour for every node on the network in their decision to reject a part=
icular block. So we need a 100% mempool synchronization across all nodes - =
otherwise just an attempted double spend could result in a fork in the netw=
ork because some nodes saw it and some didn&#39;t. And actually, if we had =
100% mempool synchronization, we wouldn&#39;t need a blockchain in the firs=
t place, because we could just use &quot;first to enter mempool&quot; as va=
lidity criterion.<br></div><div class=3D"gmail_extra"><br><div class=3D"gma=
il_quote">On Wed, Jul 1, 2015 at 1:41 AM, Peter Grigor <span dir=3D"ltr">&l=
t;<a href=3D"mailto:peter@grigor.ws" target=3D"_blank">peter@grigor.ws</a>&=
gt;</span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"margin:0 0 =
0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir=3D"ltr"><div s=
tyle=3D"font-size:12.8000001907349px">The block size debate centers around =
one concern it seems. To wit: if block size is increased malicious miners m=
ay publish unreasonably large &quot;bloated&quot; blocks. The way a miner w=
ould do this is to generate a plethora of private, non-propagated transacti=
ons and include these in the block they solve.</div><div style=3D"font-size=
:12.8000001907349px"><br></div><div style=3D"font-size:12.8000001907349px">=
It seems to me that these bloated blocks could easily be detected by other =
miners and full nodes: they will contain a very high percentage of transact=
ions that aren&#39;t found in the nodes&#39; own memory pools. This signatu=
re can be exploited to allow nodes to reject these bloated blocks. The key =
here is that any malicious miner that publishes a block that is bloated wit=
h his own transactions would contain a ridiculous number of transactions th=
at *absolutely no other full node has in its mempool*.</div><div style=3D"f=
ont-size:12.8000001907349px"><br></div><div style=3D"font-size:12.800000190=
7349px">Simply put, a threshold would be set by nodes on the allowable numb=
er of non-mempool transactions allowed in a solved block (say, maybe, 50% -=
- I really don&#39;t know what it should be). If a block is published which=
 contains more that this threshold of non-mempool transactions then it is r=
ejected.</div><div style=3D"font-size:12.8000001907349px"><br></div><div st=
yle=3D"font-size:12.8000001907349px">If this idea works the block size limi=
tation could be completely removed.</div></div>
<br>_______________________________________________<br>
bitcoin-dev mailing list<br>
<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org">bitcoin-dev@lists.=
linuxfoundation.org</a><br>
<a href=3D"https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev" =
rel=3D"noreferrer" target=3D"_blank">https://lists.linuxfoundation.org/mail=
man/listinfo/bitcoin-dev</a><br>
<br></blockquote></div><br></div>

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