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Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] BIP proposal - patch to raise selfish
mining threshold.
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Patrick, could you please explain us why the solution proposed by Ittay
would drop the actual honest miners ratio, becoming so backfire? Thanks a
lot
2013/11/5 Patrick <patrick@intersango.com>
> The ratio of honest miners that mine the first block they see is > 0.5
>
> Your proposed solution would reduce that ratio to 0.5
>
> In other words your proposed change would make the attack you describe
> easier not harder.
>
>
> On 11/05/2013 09:26 AM, Ittay wrote:
>
> 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
>>
>
>
>
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Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
<div dir=3D"ltr"><div class=3D"gmail_extra"><div><div style>Patrick, could =
you please explain us why the solution proposed by Ittay would drop the act=
ual honest miners ratio, becoming so backfire? Thanks a lot</div></div>
<br><br><div class=3D"gmail_quote">2013/11/5 Patrick <span dir=3D"ltr"><=
<a href=3D"mailto:patrick@intersango.com" target=3D"_blank">patrick@intersa=
ngo.com</a>></span><br><blockquote class=3D"gmail_quote" style=3D"margin=
:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
=20
=20
=20
<div bgcolor=3D"#FFFFFF" text=3D"#000000">
<div>The ratio of honest miners that mine
the first block they see is > 0.5<br>
<br>
Your proposed solution would reduce that ratio to 0.5<br>
<br>
In other words your proposed change would make the attack you
describe easier not harder.<div><div class=3D"h5"><br>
<br>
On 11/05/2013 09:26 AM, Ittay wrote:<br>
</div></div></div>
<blockquote type=3D"cite"><div><div class=3D"h5">
<div dir=3D"ltr">That sounds like selfish mining, and the magic
number is 25%. 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 point, 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" =
target=3D"_blank">pete@petertodd.org</a>></span>
wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;bord=
er-left:1px #ccc solid;padding-left:1ex">
<div>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><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><font color=3D"#888888"><br>
--<br>
'peter'[:-1]@<a href=3D"http://petertodd.org" targe=
t=3D"_blank">petertodd.org</a><br>
0000000000000005e25ca9b9fe62bdd6e8a2b4527ad61753dd2113c268bec707<br>
</font></span></blockquote>
</div>
<br>
</div>
<br>
<fieldset></fieldset>
<br>
</div></div><div class=3D"im"><pre>----------------------------------=
--------------------------------------------
November Webinars for C, C++, Fortran Developers
Accelerate application performance with scalable programming models. Explor=
e
techniques for threading, error checking, porting, and tuning. Get the most=
=20
from the latest Intel processors and coprocessors. See abstracts and regist=
er
<a href=3D"http://pubads.g.doubleclick.net/gampad/clk?id=3D60136231&iu=
=3D/4140/ostg.clktrk" target=3D"_blank">http://pubads.g.doubleclick.net/gam=
pad/clk?id=3D60136231&iu=3D/4140/ostg.clktrk</a></pre>
<br>
<fieldset></fieldset>
<br>
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</pre>
</div></blockquote>
<br>
</div>
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