From: Thomas Hartman <thomashartman1@gmail.com>
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Date: Wed, 19 Aug 2020 17:15:08 -0400
References: <CAHAXnDXhAFQHiBCJ=H=1ZGHdHWhgLh1rG3pCPR5o48ziZzV+zQ@mail.gmail.com>
 <CAE-z3OVCcAL2x39TswA8zrZ+yjSqdx4hccTWn9Ug8MQ5=k-Pgg@mail.gmail.com>
To: Tier Nolan <tier.nolan@gmail.com>,
 Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
In-Reply-To: <CAE-z3OVCcAL2x39TswA8zrZ+yjSqdx4hccTWn9Ug8MQ5=k-Pgg@mail.gmail.com>
Message-Id: <C4A9F1FC-8BD9-4A03-806B-5091375090B5@gmail.com>
Subject: Re: [bitcoin-dev] reviving op_difficulty
Precedence: list


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> On Aug 16, 2020, at 2:59 PM, Tier Nolan via bitcoin-dev =
<bitcoin-dev@lists.linuxfoundation.org> wrote:
>=20
> Output 0:  Pay Alice if diff < 1.00 trillion else Bob

What is included in blocks is a packed representation of the difficulty =
target, not the difficulty per se as typically reported on blockchain =
explorer.=20

https://en.bitcoin.it/wiki/Difficulty =
<https://en.bitcoin.it/wiki/Difficulty>

Perhaps what is best for speculation contracts is not the difficulty per =
se, but the ratio between some unknown future difficulty and the current =
difficulty. That is easily obtained from the packed representations =
already included in blocks. IE

Current difficulty / last difficulty =3D 1 / ( current target / last =
target )

To give a worked example, current difficulty is 16.94T, and last =
difficulty was 16.84T.=20
Current packed target is 0x17109bac, last packed target is  0x1710b4f8=09=

16.94 / 16.84 is same as 1 / ( 0x109ba / 0x10b4f8  )  (the 17 is an =
exponent in both cases so leaving it out for clarity).=20

So perhaps the way op_diff should work is take 2 packed targets, 1 known =
and 1 unknown at time of contract, and return the ratio.=20

The contract could then work as previously described, except using the =
ratio for ticks instead of the difficulty.=

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<html><head><meta http-equiv=3D"Content-Type" content=3D"text/html; =
charset=3Dus-ascii"></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; line-break: after-white-space;" class=3D""><br =
class=3D""><div><br class=3D""><blockquote type=3D"cite" class=3D""><div =
class=3D"">On Aug 16, 2020, at 2:59 PM, Tier Nolan via bitcoin-dev =
&lt;<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" =
class=3D"">bitcoin-dev@lists.linuxfoundation.org</a>&gt; wrote:</div><br =
class=3D"Apple-interchange-newline"><div class=3D""><span =
style=3D"caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: =
12px; font-style: normal; font-variant-caps: normal; font-weight: =
normal; letter-spacing: normal; text-align: start; text-indent: 0px; =
text-transform: none; white-space: normal; word-spacing: 0px; =
-webkit-text-stroke-width: 0px; text-decoration: none; float: none; =
display: inline !important;" class=3D"">Output 0:&nbsp; Pay Alice if =
diff &lt; 1.00 trillion else Bob</span></div></blockquote></div><br =
class=3D""><div class=3D""><div class=3D"">What is included in blocks is =
a packed representation of the difficulty target, not the difficulty per =
se as typically reported on blockchain explorer.&nbsp;</div><div =
class=3D""><br class=3D""></div><div class=3D""><a =
href=3D"https://en.bitcoin.it/wiki/Difficulty" =
class=3D"">https://en.bitcoin.it/wiki/Difficulty</a></div><div =
class=3D""><br class=3D""></div><div class=3D"">Perhaps what is best for =
speculation contracts is not the difficulty per se, but the ratio =
between some unknown future difficulty and the current difficulty. That =
is easily obtained from the packed representations already included in =
blocks. IE</div><div class=3D""><br class=3D""></div><div =
class=3D"">Current difficulty / last difficulty =3D 1 / ( current target =
/ last target )</div><div class=3D""><br class=3D""></div><div =
class=3D"">To give a worked example, current difficulty is 16.94T, and =
last difficulty was 16.84T.&nbsp;</div><div class=3D"">Current packed =
target is 0x17109bac, last packed target is &nbsp;0x1710b4f8<span =
class=3D"Apple-tab-span" style=3D"white-space:pre">	=
</span></div><div class=3D"">16.94 / 16.84 is same as 1 / ( 0x109ba / =
0x10b4f8 &nbsp;) &nbsp;(the 17 is an exponent in both cases so leaving =
it out for clarity).&nbsp;</div><div class=3D""><br class=3D""></div><div =
class=3D"">So perhaps the way op_diff should work is take 2 packed =
targets, 1 known and 1 unknown at time of contract, and return the =
ratio.&nbsp;</div><div class=3D""><br class=3D""></div><div class=3D"">The=
 contract could then work as previously described, except using the =
ratio for ticks instead of the difficulty.</div></div></body></html>=

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