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Date: Wed, 11 May 2016 11:28:42 -0700
Message-ID: <CAH6h1LsRgZEar8JDR2m-hsTc-DE+=A6BzOq_X2CHSya=bxFRQQ@mail.gmail.com>
From: Timo Hanke <timo.hanke@web.de>
To: Luke Dashjr <luke@dashjr.org>, 
	Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Content-Type: multipart/alternative; boundary=001a11360dae1f85b8053295363b
Subject: Re: [bitcoin-dev] Making AsicBoost irrelevant
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Sorry, you must have meant all 12 bytes. That makes finding a collision
substantially harder. However, you may have to restrict yourself to 10
bytes because you don't know if any hardware does timestamp rolling
on-chip. Also you create an incentive to mess around with the version bits
instead, so you would have to fix that as well. So it basically means a new
mining header with the real blockheader as a child header.

On Wed, May 11, 2016 at 9:24 AM, Timo Hanke <timo.hanke@web.de> wrote:

> Luke, do you mean to replace the first 4 bytes of the second chunk (bytes
> 64..67 in 0-based counting) by the XOR of those 4 bytes with the first 4
> bytes of the midstate? (I assume you don't care about 12 bytes but rather
> those 4 bytes.)
>
> This does not work. All it does is adding another computational step
> before you can check for a collision in those 4 bytes. It makes finding a
> collision only marginally harder.
>
> On Wed, May 11, 2016 at 7:28 AM, Luke Dashjr via bitcoin-dev <
> bitcoin-dev@lists.linuxfoundation.org> wrote:
>
>> On Wednesday, May 11, 2016 12:20:55 PM Sergio Demian Lerner via
>> bitcoin-dev
>> wrote:
>> > On Tue, May 10, 2016 at 6:43 PM, Sergio Demian Lerner <
>> > sergio.d.lerner@gmail.com> wrote:
>> > > You can find it here:
>> > >
>> https://bitslog.wordpress.com/2014/03/18/the-re-design-of-the-bitcoin-blo
>> > > ck-header/
>> > >
>> > > Basically, the idea is to put in the first 64 bytes a 4 byte hash of
>> the
>> > > second 64-byte chunk. That design also allows increased nonce space in
>> > > the first 64 bytes.
>> >
>> > My mistake here. I didn't recalled correctly my own idea. The idea is to
>> > include in the second 64-byte chunk a 4-byte hash of the first chunk,
>> not
>> > the opposite.
>>
>> What if we XOR bytes 64..76 with the first 12 bytes of the SHA2 midstate?
>> Would that work?
>>
>> Luke
>> _______________________________________________
>> 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">Sorry, you must have meant all 12 bytes. That makes findin=
g a collision substantially harder. However, you may have to restrict yours=
elf to 10 bytes because you don&#39;t know if any hardware does timestamp r=
olling on-chip. Also you create an incentive to mess around with the versio=
n bits instead, so you would have to fix that as well. So it basically mean=
s a new mining header with the real blockheader as a child header.=C2=A0</d=
iv><div class=3D"gmail_extra"><br><div class=3D"gmail_quote">On Wed, May 11=
, 2016 at 9:24 AM, Timo Hanke <span dir=3D"ltr">&lt;<a href=3D"mailto:timo.=
hanke@web.de" target=3D"_blank">timo.hanke@web.de</a>&gt;</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 dir=3D"ltr">Luke, do you mean to replac=
e the first 4 bytes of the second chunk (bytes 64..67 in 0-based counting) =
by the XOR of those 4 bytes with the first 4 bytes of the midstate? (I assu=
me you don&#39;t care about 12 bytes but rather those 4 bytes.)<div><br></d=
iv><div>This does not work. All it does is adding another computational ste=
p before you can check for a collision in those 4 bytes. It makes finding a=
 collision only marginally harder.</div></div><div class=3D"HOEnZb"><div cl=
ass=3D"h5"><div class=3D"gmail_extra"><br><div class=3D"gmail_quote">On Wed=
, May 11, 2016 at 7:28 AM, Luke Dashjr via bitcoin-dev <span dir=3D"ltr">&l=
t;<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" target=3D"_blank=
">bitcoin-dev@lists.linuxfoundation.org</a>&gt;</span> wrote:<br><blockquot=
e class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc sol=
id;padding-left:1ex">On Wednesday, May 11, 2016 12:20:55 PM Sergio Demian L=
erner via bitcoin-dev<br>
wrote:<br>
<div><div>&gt; On Tue, May 10, 2016 at 6:43 PM, Sergio Demian Lerner &lt;<b=
r>
&gt; <a href=3D"mailto:sergio.d.lerner@gmail.com" target=3D"_blank">sergio.=
d.lerner@gmail.com</a>&gt; wrote:<br>
&gt; &gt; You can find it here:<br>
&gt; &gt; <a href=3D"https://bitslog.wordpress.com/2014/03/18/the-re-design=
-of-the-bitcoin-blo" rel=3D"noreferrer" target=3D"_blank">https://bitslog.w=
ordpress.com/2014/03/18/the-re-design-of-the-bitcoin-blo</a><br>
&gt; &gt; ck-header/<br>
&gt; &gt;<br>
&gt; &gt; Basically, the idea is to put in the first 64 bytes a 4 byte hash=
 of the<br>
&gt; &gt; second 64-byte chunk. That design also allows increased nonce spa=
ce in<br>
&gt; &gt; the first 64 bytes.<br>
&gt;<br>
&gt; My mistake here. I didn&#39;t recalled correctly my own idea. The idea=
 is to<br>
&gt; include in the second 64-byte chunk a 4-byte hash of the first chunk, =
not<br>
&gt; the opposite.<br>
<br>
</div></div>What if we XOR bytes 64..76 with the first 12 bytes of the SHA2=
 midstate?<br>
Would that work?<br>
<br>
Luke<br>
<div><div>_______________________________________________<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>
</div></div></blockquote></div><br></div>
</div></div></blockquote></div><br></div>

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