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From: Eric Voskuil <eric@voskuil.org>
In-Reply-To: <CA+XQW1j2vNNswEQ-HVWF9MpyGBzmq3ij+v=2NGH2VicQ63=v6A@mail.gmail.com>
Date: Mon, 6 Nov 2017 12:55:29 -0800
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References: <CAB0O3SVjhG19R61B78hFCPwfwWemTXj=tOsvgAgoNbjFYXXAtg@mail.gmail.com>
	<20171106195000.GA7245@fedora-23-dvm>
	<CA+XQW1j2vNNswEQ-HVWF9MpyGBzmq3ij+v=2NGH2VicQ63=v6A@mail.gmail.com>
To: Paul Sztorc <truthcoin@gmail.com>,
	Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Introducing a POW through a soft-fork
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If a block that would be discarded under previous rules becomes accepted aft=
er a rule addition, there is no reason to not simply call the new rule a har=
d fork. IOW it's perfectly rational to consider a weaker block as "invalid" r=
elative to the strong chain. As such I don't see any reason to qualify the t=
erm, it's a hard fork. But Peter's observation (the specific behavior) is ul=
timately what matters.

e

> On Nov 6, 2017, at 12:30, Paul Sztorc via bitcoin-dev <bitcoin-dev@lists.l=
inuxfoundation.org> wrote:
>=20
> +1 to all of Peter Todd's comments
>=20
>> On Nov 6, 2017 11:50 AM, "Peter Todd via bitcoin-dev" <bitcoin-dev@lists.=
linuxfoundation.org> wrote:
>> On Wed, Nov 01, 2017 at 05:48:27AM +0000, Devrandom via bitcoin-dev wrote=
:
>>=20
>> Some quick thoughts...
>>=20
>> > Hi all,
>> >
>> > Feedback is welcome on the draft below.  In particular, I want to see i=
f
>> > there is interest in further development of the idea and also intereste=
d in
>> > any attack vectors or undesirable dynamics.
>> >
>> > (Formatted version available here:
>> > https://github.com/devrandom/btc-papers/blob/master/aux-pow.md )
>> >
>> > # Soft-fork Introduction of a New POW
>>=20
>> First of all, I don't think you can really call this a soft-fork; I'd cal=
l it a
>> "pseudo-soft-fork"
>>=20
>> My reasoning being that after implementation, a chain with less total wor=
k than
>> the main chain - but more total SHA256^2 work than the main chain - might=
 be
>> followed by non-supporting clients. It's got some properties of a soft-fo=
rk,
>> but it's security model is definitely different.
>>=20
>> > ### Aux POW intermediate block
>> >
>> > Auxiliary POW blocks are introduced between normal blocks - i.e. the ch=
ain
>> > alternates between the two POWs.
>> > Each aux-POW block points to the previous normal block and contains
>> > transactions just like a normal block.
>> > Each normal block points to the previous aux-POW block and must contain=
 all
>> > transactions from the aux-POW block.
>>=20
>> Note how you're basically proposing for the block interval to be decrease=
d,
>> which has security implications due to increased orphan rates.
>>=20
>> > ### Heaviest chain rule change
>> >
>> > This is a semi-hard change, because non-upgraded nodes can get on the w=
rong
>> > chain in case of attack.  However,
>>=20
>> Exactly! Not really a soft-fork.
>>=20
>> --
>> https://petertodd.org 'peter'[:-1]@petertodd.org
>>=20
>> _______________________________________________
>> bitcoin-dev mailing list
>> bitcoin-dev@lists.linuxfoundation.org
>> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>>=20
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev

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<html><head><meta http-equiv=3D"content-type" content=3D"text/html; charset=3D=
utf-8"></head><body dir=3D"auto"><div></div><div>If a block that would be di=
scarded under previous rules becomes accepted after a rule addition, there i=
s no reason to not simply call the new rule a hard fork. IOW it's perfectly r=
ational to consider a weaker block as "invalid" relative to the strong chain=
. As such I don't see any reason to qualify the term, it's a hard fork. But P=
eter's observation (the specific behavior) is ultimately what matters.</div>=
<div><br></div><div>e</div><div><br>On Nov 6, 2017, at 12:30, Paul Sztorc vi=
a bitcoin-dev &lt;<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org">b=
itcoin-dev@lists.linuxfoundation.org</a>&gt; wrote:<br><br></div><blockquote=
 type=3D"cite"><div><div dir=3D"auto">+1 to all of Peter Todd's comments</di=
v><div class=3D"gmail_extra"><br><div class=3D"gmail_quote">On Nov 6, 2017 1=
1:50 AM, "Peter Todd via bitcoin-dev" &lt;<a href=3D"mailto:bitcoin-dev@list=
s.linuxfoundation.org">bitcoin-dev@lists.linuxfoundation.org</a>&gt; wrote:<=
br type=3D"attribution"><blockquote class=3D"gmail_quote" style=3D"margin:0 0=
 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">On Wed, Nov 01, 2017 at=
 05:48:27AM +0000, Devrandom via bitcoin-dev wrote:<br>
<br>
Some quick thoughts...<br>
<br>
&gt; Hi all,<br>
&gt;<br>
&gt; Feedback is welcome on the draft below.&nbsp; In particular, I want to s=
ee if<br>
&gt; there is interest in further development of the idea and also intereste=
d in<br>
&gt; any attack vectors or undesirable dynamics.<br>
&gt;<br>
&gt; (Formatted version available here:<br>
&gt; <a href=3D"https://github.com/devrandom/btc-papers/blob/master/aux-pow.=
md" rel=3D"noreferrer" target=3D"_blank">https://github.com/devrandom/<wbr>b=
tc-papers/blob/master/aux-<wbr>pow.md</a> )<br>
&gt;<br>
&gt; # Soft-fork Introduction of a New POW<br>
<br>
First of all, I don't think you can really call this a soft-fork; I'd call i=
t a<br>
"pseudo-soft-fork"<br>
<br>
My reasoning being that after implementation, a chain with less total work t=
han<br>
the main chain - but more total SHA256^2 work than the main chain - might be=
<br>
followed by non-supporting clients. It's got some properties of a soft-fork,=
<br>
but it's security model is definitely different.<br>
<br>
&gt; ### Aux POW intermediate block<br>
&gt;<br>
&gt; Auxiliary POW blocks are introduced between normal blocks - i.e. the ch=
ain<br>
&gt; alternates between the two POWs.<br>
&gt; Each aux-POW block points to the previous normal block and contains<br>=

&gt; transactions just like a normal block.<br>
&gt; Each normal block points to the previous aux-POW block and must contain=
 all<br>
&gt; transactions from the aux-POW block.<br>
<br>
Note how you're basically proposing for the block interval to be decreased,<=
br>
which has security implications due to increased orphan rates.<br>
<br>
&gt; ### Heaviest chain rule change<br>
&gt;<br>
&gt; This is a semi-hard change, because non-upgraded nodes can get on the w=
rong<br>
&gt; chain in case of attack.&nbsp; However,<br>
<br>
Exactly! Not really a soft-fork.<br>
<br>
--<br>
<a href=3D"https://petertodd.org" rel=3D"noreferrer" target=3D"_blank">https=
://petertodd.org</a> 'peter'[:-1]@<a href=3D"http://petertodd.org" rel=3D"no=
referrer" target=3D"_blank">petertodd.org</a><br>
<br>______________________________<wbr>_________________<br>
bitcoin-dev mailing list<br>
<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org">bitcoin-dev@lists.<=
wbr>linuxfoundation.org</a><br>
<a href=3D"https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev" r=
el=3D"noreferrer" target=3D"_blank">https://lists.linuxfoundation.<wbr>org/m=
ailman/listinfo/bitcoin-<wbr>dev</a><br>
<br></blockquote></div></div>
</div></blockquote><blockquote type=3D"cite"><div><span>____________________=
___________________________</span><br><span>bitcoin-dev mailing list</span><=
br><span><a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org">bitcoin-de=
v@lists.linuxfoundation.org</a></span><br><span><a href=3D"https://lists.lin=
uxfoundation.org/mailman/listinfo/bitcoin-dev">https://lists.linuxfoundation=
.org/mailman/listinfo/bitcoin-dev</a></span><br></div></blockquote></body></=
html>=

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