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From: Nathan Cook <nathan.cook@gmail.com>
Date: Wed, 5 Oct 2016 05:15:36 +0300
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To: Luke Dashjr <luke@dashjr.org>, 
	Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
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Subject: Re: [bitcoin-dev] BIP draft: OP_CHECKBLOCKATHEIGHT
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On 1 October 2016 at 08:02, Luke Dashjr via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> On Saturday, October 01, 2016 4:01:04 AM Rusty Russell wrote:
>
> > - Otherwise <bits> of hash is compared to lower <bits> of blockhash.
>
> Lower in what endian? Why only that endian? Why only lower? I can see a
> possible use case where one wants to look at only the high bits to ensure
> their transaction is only valid in a block with at least a certain
> difficulty...


Why not use segwit versioning for all this stuff? That lets you re-enable
the bitwise operations like OP_AND, permitting arbitrary bit-masks.
Further, the "at least a certain difficulty" problem suggests a solution by
extending the validity of opcodes like OP_LESSTHAN etc. to 256-bit inputs.

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<div dir=3D"ltr"><div class=3D"gmail_extra"><br><div class=3D"gmail_quote">=
On 1 October 2016 at 08:02, Luke Dashjr via bitcoin-dev <span dir=3D"ltr">&=
lt;<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" target=3D"_blan=
k">bitcoin-dev@lists.linuxfoundation.org</a>&gt;</span> wrote:<br><blockquo=
te class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px =
solid rgb(204,204,204);padding-left:1ex"><span class=3D"gmail-">On Saturday=
, October 01, 2016 4:01:04 AM Rusty Russell wrote:<br></span><span class=3D=
"gmail-"><br>
&gt; - Otherwise &lt;bits&gt; of hash is compared to lower &lt;bits&gt; of =
blockhash.<br>
<br>
</span>Lower in what endian? Why only that endian? Why only lower? I can se=
e a<br>
possible use case where one wants to look at only the high bits to ensure<b=
r>
their transaction is only valid in a block with at least a certain<br>
difficulty...</blockquote><div><br></div><div>Why not use segwit versioning=
 for all this stuff? That lets you re-enable the bitwise operations like OP=
_AND, permitting arbitrary bit-masks. Further, the &quot;at least a certain=
 difficulty&quot; problem suggests a solution by extending the validity of =
opcodes like OP_LESSTHAN etc. to 256-bit inputs.</div></div></div></div>

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