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From: Mike Brooks <m@ib.tc>
Date: Thu, 8 Oct 2020 16:05:05 -0700
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To: ZmnSCPxj <ZmnSCPxj@protonmail.com>, 
 Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
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Subject: Re: [bitcoin-dev] Progress on Miner Withholding - FPNC
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Very interesting,

Block mixing did not resolve the selfish mining that is currently observed
on the network.  This mitigation was only intended to limit the maximum
impact of waiting for a 2nd block to be produced.

Rebalancing the selfish-mining incentives with FPNC and a faster block
creation time is the single best thing we can do to decentralize mining
efforts.  It will also produce a better network.



On Wed, Oct 7, 2020 at 6:40 PM ZmnSCPxj via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> Good morning all,
>
> >
> > Below is a novel discussion on block-withholding attacks and FPNC. Thes=
e
> are two very simple changes being proposed here that will
> dramatically impact the network for the better.
> >
> > But first of all, I'd like to say that the idea for FPNC came out of a
> conversation with ZmnSCPxj's in regards to re-org stability.  When I had
> proposed blockchain pointers with the PubRef opcode, he took the time to
> explain to me concerns around re-orgs and why it is a bigger problem than=
 I
> initially had thought =E2=80=94 and I greatly appreciate this detail.   A=
fter
> touching base with ZmnSCPxj and Greg Maxwell there is an overwhelming vie=
w
> that the current problems that face the network outweigh any theoretical
> ones.
> >
> > Currently the elephant in the room is the miner withholding
> attack. There is an unintended incentive to hold onto blocks because
> keeping knowledge of this coinbase private gives a greedy miner more time
> to calculate the next block.  Major mining pools are actively employing
> this strategy because winning two blocks in a row has a much greater payo=
ff
> than common robbery. This unfair advantage happens each time a new block =
is
> found, and provides a kind of home-field advantage for large pools, and
> contributes to a more centralized network. This odd feature of the bitcoi=
n
> protocol provides a material incentive to delay transactions and encourag=
es
> the formation of disagreements. In a sense, withholding is a deception of
> the computational power of a miner, and by extension a deception of their
> influence within the electorate.  In effect, other miners are forced to
> work harder, and when they are successful in finding a 2nd solution of th=
e
> same height =E2=80=94 no one benefits. Disagreement on the bitcoin networ=
k is not
> good for the environment, or for the users, or for honest miners, but is
> ideal for dishonest miners looking for an advantage.
>
> This is my understanding:
>
> The selfish mining attack described above was already presented and known
> about **many years** ago, with the solution presented here:
> https://www.cs.cornell.edu/~ie53/publications/btcProcFC.pdf
>
> The solution was later determined to actually raise the needed threshhold
> to 33%, not 25% in the paper.
>
> That solution is what is used in the network today.
>
> Implementing floating-point Nakamoto Consensus removes the solution
> presented in the paper, and therefore risks reintroducing the selfish
> mining attack.
>
> Therefore, floating-point Nakamoto Consensus is a hard NAK.
>
>
> Regards,
> ZmnSCPxj
>
> _______________________________________________
> 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">Very interesting,<div><br></div><div>Block mixing did not =
resolve the selfish mining that is currently observed on the network.=C2=A0=
 This mitigation was only=C2=A0intended to limit the maximum impact of wait=
ing for a 2nd block to be produced.</div><div><br></div><div>Rebalancing=C2=
=A0the selfish-mining incentives with FPNC and a faster block creation=C2=
=A0time is the single best thing we can do to decentralize mining efforts.=
=C2=A0 It will also produce a better network.</div><div><br></div></div><di=
v dir=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote"><di=
v dir=3D"ltr" class=3D"gmail_attr">On Wed, Oct 7, 2020 at 6:40 PM ZmnSCPxj =
via bitcoin-dev &lt;<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org=
" target=3D"_blank">bitcoin-dev@lists.linuxfoundation.org</a>&gt; wrote:<br=
></div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;=
border-left:1px solid rgb(204,204,204);padding-left:1ex">Good morning all,<=
br>
<br>
&gt;<br>
&gt; Below is a novel discussion=C2=A0on block-withholding=C2=A0attacks and=
 FPNC. These are=C2=A0two very simple changes being proposed here that will=
 dramatically=C2=A0impact the network for the better.<br>
&gt;<br>
&gt; But first of all, I&#39;d like to say that the idea for FPNC came out =
of a conversation=C2=A0with ZmnSCPxj&#39;s in regards to=C2=A0re-org stabil=
ity.=C2=A0 When I had proposed blockchain pointers with the PubRef opcode, =
he took the time to explain to me concerns around re-orgs and why it is a b=
igger problem than I initially had thought=C2=A0=E2=80=94 and I greatly app=
reciate this detail.=C2=A0 =C2=A0After touching base with ZmnSCPxj and Greg=
 Maxwell there is an overwhelming view that the current problems that face =
the network outweigh any theoretical ones.<br>
&gt;<br>
&gt; Currently the elephant in the room is the miner withholding attack.=C2=
=A0There is an unintended incentive to hold onto blocks because keeping kno=
wledge of this coinbase private gives a greedy miner more time to calculate=
 the next block.=C2=A0 Major mining pools are actively employing this strat=
egy because winning two blocks in a row has a much greater payoff than comm=
on robbery. This unfair advantage=C2=A0happens each time a=C2=A0new block i=
s found, and provides a kind of home-field advantage for large pools, and c=
ontributes to a more centralized network. This odd feature of the bitcoin p=
rotocol provides a material incentive to delay transactions and encourages =
the formation of disagreements. In a sense, withholding is a deception of t=
he computational power of a miner, and by extension a deception of their in=
fluence within the electorate.=C2=A0 In effect, other miners are forced to =
work harder,=C2=A0and when they are successful in finding a 2nd solution of=
 the same height=C2=A0=E2=80=94 no one benefits. Disagreement on the bitcoi=
n network is not good for the environment, or for the users, or for honest =
miners, but is ideal for dishonest miners looking for an advantage.<br>
<br>
This is my understanding:<br>
<br>
The selfish mining attack described above was already presented and known a=
bout **many years** ago, with the solution presented here: <a href=3D"https=
://www.cs.cornell.edu/~ie53/publications/btcProcFC.pdf" rel=3D"noreferrer" =
target=3D"_blank">https://www.cs.cornell.edu/~ie53/publications/btcProcFC.p=
df</a><br>
<br>
The solution was later determined to actually raise the needed threshhold t=
o 33%, not 25% in the paper.<br>
<br>
That solution is what is used in the network today.<br>
<br>
Implementing floating-point Nakamoto Consensus removes the solution present=
ed in the paper, and therefore risks reintroducing the selfish mining attac=
k.<br>
<br>
Therefore, floating-point Nakamoto Consensus is a hard NAK.<br>
<br>
<br>
Regards,<br>
ZmnSCPxj<br>
<br>
_______________________________________________<br>
bitcoin-dev mailing list<br>
<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" target=3D"_blank">=
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>
</blockquote></div></div>

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