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Cc: Ittay <ittay.eyal@cornell.edu>,
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Subject: Re: [Bitcoin-development] BIP proposal - patch to raise selfish
mining threshold.
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--089e013d1b667b3d6c04ea7157d7
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That sounds like selfish mining, and the magic number is 25%. That's the
minimal pool size.
Today the threshold is 0% with good connectivity.
If I misunderstood your point, please elaborate.
Ittay
On Tue, Nov 5, 2013 at 12:05 PM, Peter Todd <pete@petertodd.org> wrote:
> On Tue, Nov 05, 2013 at 11:56:53AM -0500, Ittay wrote:
> > Hello,
> >
> > Please see below our BIP for raising the selfish mining threshold.
> > Looking forward to your comments.
>
> <snip>
>
> > 2. No new vulnerabilities introduced:
> > Currently the choice among equal-length chains is done arbitrarily,
> > depending on network topology. This arbitrariness is a source of
> > vulnerability. We replace it with explicit randomness, which is at the
> > control of the protocol. The change does not introduce executions that
> were
> > not possible with the old protocol.
>
> Credit goes to Gregory Maxwell for pointing this out, but the random
> choice solution does in fact introduce a vulnerability in that it
> creates incentives for pools over a certain size to withhold blocks
> rather than immediately broadcasting all blocks found.
>
> The problem is that when the pool eventually choses to reveal the block
> they mined, 50% of the hashing power switches, thus splitting the
> network. Like the original attack this can be to their benefit. For
> pools over a certain size this strategy is profitable even without
> investing in a low-latency network; Maxwell or someone else can chime in
> with the details for deriving that threshold.
>
> I won't get a chance to for a few hours, but someone should do the
> analysis on a deterministic switching scheme.
>
> --
> 'peter'[:-1]@petertodd.org
> 0000000000000005e25ca9b9fe62bdd6e8a2b4527ad61753dd2113c268bec707
>
--089e013d1b667b3d6c04ea7157d7
Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
<div dir=3D"ltr">That sounds like selfish mining, and the magic number is 2=
5%. That's the minimal pool size.=A0<div>Today the threshold is 0% with=
good connectivity.=A0</div><div><br></div><div>If I misunderstood your poi=
nt, please elaborate.=A0</div>
<div><br></div><div>Ittay=A0</div><div><br></div></div><div class=3D"gmail_=
extra"><br><br><div class=3D"gmail_quote">On Tue, Nov 5, 2013 at 12:05 PM, =
Peter Todd <span dir=3D"ltr"><<a href=3D"mailto:pete@petertodd.org" targ=
et=3D"_blank">pete@petertodd.org</a>></span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex"><div class=3D"im">On Tue, Nov 05, 2013 at 11=
:56:53AM -0500, Ittay wrote:<br>
> Hello,<br>
><br>
> Please see below our BIP for raising the selfish mining threshold.<br>
> Looking forward to your comments.<br>
<br>
</div><snip><br>
<div class=3D"im"><br>
> 2. No new vulnerabilities introduced:<br>
> Currently the choice among equal-length chains is done arbitrarily,<br=
>
> depending on network topology. This arbitrariness is a source of<br>
> vulnerability. We replace it with explicit randomness, which is at the=
<br>
> control of the protocol. The change does not introduce executions that=
were<br>
> not possible with the old protocol.<br>
<br>
</div>Credit goes to Gregory Maxwell for pointing this out, but the random<=
br>
choice solution does in fact introduce a vulnerability in that it<br>
creates incentives for pools over a certain size to withhold blocks<br>
rather than immediately broadcasting all blocks found.<br>
<br>
The problem is that when the pool eventually choses to reveal the block<br>
they mined, 50% of the hashing power switches, thus splitting the<br>
network. Like the original attack this can be to their benefit. For<br>
pools over a certain size this strategy is profitable even without<br>
investing in a low-latency network; Maxwell or someone else can chime in<br=
>
with the details for deriving that threshold.<br>
<br>
I won't get a chance to for a few hours, but someone should do the<br>
analysis on a deterministic switching scheme.<br>
<span class=3D"HOEnZb"><font color=3D"#888888"><br>
--<br>
'peter'[:-1]@<a href=3D"http://petertodd.org" target=3D"_blank">pet=
ertodd.org</a><br>
0000000000000005e25ca9b9fe62bdd6e8a2b4527ad61753dd2113c268bec707<br>
</font></span></blockquote></div><br></div>
--089e013d1b667b3d6c04ea7157d7--
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