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	<1804222.7gVHPiWqto@kiwi> <201602062046.40193.luke@dashjr.org>
Date: Sun, 7 Feb 2016 09:16:02 -0500
Message-ID: <CABsx9T0N_TBbmy3xr-mqNDdKVF_3_QHYA1W2ttsZBQnt4dWxgw@mail.gmail.com>
From: Gavin Andresen <gavinandresen@gmail.com>
To: Luke Dashjr <luke@dashjr.org>
Content-Type: multipart/alternative; boundary=001a11c376dc69863f052b2eb9ad
Cc: Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] BIP proposal: Increase block size limit to 2
	megabytes
Precedence: list

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On Sat, Feb 6, 2016 at 3:46 PM, Luke Dashjr via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> On Saturday, February 06, 2016 5:25:21 PM Tom Zander via bitcoin-dev wrot=
e:
> > On Saturday, February 06, 2016 06:09:21 PM Jorge Tim=C3=B3n via bitcoin=
-dev
> wrote:
> > > None of the reasons you list say anything about the fact that "being
> > > lost" (kicked out of the network) is a problem for those node's users=
.
> >
> > That's because its not.
> >
> > If you have a node that is "old" your node will stop getting new blocks=
.
> > The node will essentially just say "x-hours behind" with "x" getting
> larger
> > every hour. Funds don't get confirmed. etc.
>
> Until someone decides to attack you. Then you'll get 6, 10, maybe more
> blocks
> confirming a large 10000 BTC payment. If you're just a normal end user (o=
r
> perhaps an automated system), you'll figure that payment is good and
> irreversibly hand over the title to the house.
>

There will be approximately zero percentage of hash power left on the
weaker branch of the fork, based on past soft-fork adoption by miners (they
upgrade VERY quickly from 75% to over 95%).

So it will take a week to get 6 confirmations.

If you are a full node, you are warned that your software is obsolete and
you must upgrade.

If you are a lightweight node, it SHOULD tell you something is wrong, but
even if it doesn't, given that people running lightweight nodes run them so
they don't have to be connected to the network 24/7, it is very likely
during that week you disconnect and reconnect to the network several times.
And every time you do that you increase your chances that you will connect
to full nodes on the majority branch of the chain, where you will be told
about the double-spend.

All of that is assuming that there is no OTHER mitigation done. DNS seeds
should avoid reporting nodes that look like they are in the middle of
initial block download (that are at a block height significantly behind the
rest of the network), for example.

--=20
--
Gavin Andresen

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<div dir=3D"ltr"><div class=3D"gmail_extra"><div class=3D"gmail_quote">On S=
at, Feb 6, 2016 at 3:46 PM, Luke Dashjr via bitcoin-dev <span dir=3D"ltr">&=
lt;<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" target=3D"_blan=
k">bitcoin-dev@lists.linuxfoundation.org</a>&gt;</span> wrote:<br><blockquo=
te class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc so=
lid;padding-left:1ex"><span class=3D"">On Saturday, February 06, 2016 5:25:=
21 PM Tom Zander via bitcoin-dev wrote:<br>
&gt; On Saturday, February 06, 2016 06:09:21 PM Jorge Tim=C3=B3n via bitcoi=
n-dev<br>
wrote:<br>
&gt; &gt; None of the reasons you list say anything about the fact that &qu=
ot;being<br>
&gt; &gt; lost&quot; (kicked out of the network) is a problem for those nod=
e&#39;s users.<br>
&gt;<br>
&gt; That&#39;s because its not.<br>
&gt;<br>
&gt; If you have a node that is &quot;old&quot; your node will stop getting=
 new blocks.<br>
&gt; The node will essentially just say &quot;x-hours behind&quot; with &qu=
ot;x&quot; getting larger<br>
&gt; every hour. Funds don&#39;t get confirmed. etc.<br>
<br>
</span>Until someone decides to attack you. Then you&#39;ll get 6, 10, mayb=
e more blocks<br>
confirming a large 10000 BTC payment. If you&#39;re just a normal end user =
(or<br>
perhaps an automated system), you&#39;ll figure that payment is good and<br=
>
irreversibly hand over the title to the house.<br></blockquote><div><br></d=
iv><div>There will be approximately zero percentage of hash power left on t=
he weaker branch of the fork, based on past soft-fork adoption by miners (t=
hey upgrade VERY quickly from 75% to over 95%).</div><div><br></div><div>So=
 it will take a week to get 6 confirmations.</div><div><br></div><div>If yo=
u are a full node, you are warned that your software is obsolete and you mu=
st upgrade.</div><div><br></div><div>If you are a lightweight node, it SHOU=
LD tell you something is wrong, but even if it doesn&#39;t, given that peop=
le running lightweight nodes run them so they don&#39;t have to be connecte=
d to the network 24/7, it is very likely during that week you disconnect an=
d reconnect to the network several times. And every time you do that you in=
crease your chances that you will connect to full nodes on the majority bra=
nch of the chain, where you will be told about the double-spend.</div><div>=
<br></div><div>All of that is assuming that there is no OTHER mitigation do=
ne. DNS seeds should avoid reporting nodes that look like they are in the m=
iddle of initial block download (that are at a block height significantly b=
ehind the rest of the network), for example.</div></div><div><br></div>-- <=
br><div class=3D"gmail_signature"><div dir=3D"ltr"><div><div dir=3D"ltr"><d=
iv>--<br>Gavin Andresen<br></div><div><br></div></div></div></div></div>
</div></div>

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