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From: Mike Hearn <mike@plan99.net>
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Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] Committing to extra block data/a better
merge-mine standard
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--001a11c30bf06aed0804ea5f8024
Content-Type: text/plain; charset=UTF-8
Yes, sure. I was talking about the case of transiently relayed data, like
IP addresses.
On Mon, Nov 4, 2013 at 8:53 PM, Mark Friedenbach <mark@monetize.io> wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> On 11/4/13 11:38 AM, Mike Hearn wrote:
> > The Merkle branch doesn't get stored indefinitely though, whereas
> > the coinbase hash does. The data stored in the coinbase [output]
> > can always just be the 256-bit root hash truncated to less.
> >
> > I doubt the additional bytes make much difference really, so the
> > additional complexity may not be worth it. But it wouldn't be an
> > issue to do.
>
> The bits make a difference if you are merged mining. You can use the
> birthday attack to construct two data trees whose hash match the
> (truncated) value, each containing separate aux block headers. This
> allows you to double-count the bitcoin PoW for more than one aux block
> on the same chain, potentially facilitating aux chain attacks.
>
> If you want 128 bits of security for merged mined aux chains, you need
> 256 bits of hash in the coinbase.
> -----BEGIN PGP SIGNATURE-----
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>
>
> ------------------------------------------------------------------------------
> Android is increasing in popularity, but the open development platform that
> developers love is also attractive to malware creators. Download this white
> paper to learn more about secure code signing practices that can help keep
> Android apps secure.
> http://pubads.g.doubleclick.net/gampad/clk?id=65839951&iu=/4140/ostg.clktrk
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--001a11c30bf06aed0804ea5f8024
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
<div dir=3D"ltr">Yes, sure. I was talking about the case of transiently rel=
ayed data, like IP addresses.</div><div class=3D"gmail_extra"><br><br><div =
class=3D"gmail_quote">On Mon, Nov 4, 2013 at 8:53 PM, Mark Friedenbach <spa=
n dir=3D"ltr"><<a href=3D"mailto:mark@monetize.io" target=3D"_blank">mar=
k@monetize.io</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">-----BEGIN PGP SIGNED MESS=
AGE-----<br>
Hash: SHA1<br>
<br>
</div><div class=3D"im">On 11/4/13 11:38 AM, Mike Hearn wrote:<br>
> The Merkle branch doesn't get stored indefinitely though, whereas<=
br>
> the coinbase hash does. The data stored in the coinbase [output]<br>
> can always just be the 256-bit root hash truncated to less.<br>
><br>
> I doubt the additional bytes make much difference really, so the<br>
> additional complexity may not be worth it. But it wouldn't be an<b=
r>
> issue to do.<br>
<br>
</div>The bits make a difference if you are merged mining. You can use the<=
br>
birthday attack to construct two data trees whose hash match the<br>
(truncated) value, each containing separate aux block headers. This<br>
allows you to double-count the bitcoin PoW for more than one aux block<br>
on the same chain, potentially facilitating aux chain attacks.<br>
<br>
If you want 128 bits of security for merged mined aux chains, you need<br>
256 bits of hash in the coinbase.<br>
<div class=3D"im">-----BEGIN PGP SIGNATURE-----<br>
Version: GnuPG/MacGPG2 v2.0.19 (Darwin)<br>
Comment: GPGTools - <a href=3D"http://gpgtools.org" target=3D"_blank">http:=
//gpgtools.org</a><br>
Comment: Using GnuPG with Thunderbird - <a href=3D"http://www.enigmail.net/=
" target=3D"_blank">http://www.enigmail.net/</a><br>
<br>
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=3DnydG<br>
<div class=3D"HOEnZb"><div class=3D"h5">-----END PGP SIGNATURE-----<br>
<br>
---------------------------------------------------------------------------=
---<br>
Android is increasing in popularity, but the open development platform that=
<br>
developers love is also attractive to malware creators. Download this white=
<br>
paper to learn more about secure code signing practices that can help keep<=
br>
Android apps secure.<br>
<a href=3D"http://pubads.g.doubleclick.net/gampad/clk?id=3D65839951&iu=
=3D/4140/ostg.clktrk" target=3D"_blank">http://pubads.g.doubleclick.net/gam=
pad/clk?id=3D65839951&iu=3D/4140/ostg.clktrk</a><br>
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Bitcoin-development mailing list<br>
<a href=3D"mailto:Bitcoin-development@lists.sourceforge.net">Bitcoin-develo=
pment@lists.sourceforge.net</a><br>
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" target=3D"_blank">https://lists.sourceforge.net/lists/listinfo/bitcoin-de=
velopment</a><br>
</div></div></blockquote></div><br></div>
--001a11c30bf06aed0804ea5f8024--
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