From: Tamas Blummer <tamas.blummer@gmail.com>
Message-Id: <2502B467-092D-45A6-8F7B-9E3D08D5BB15@gmail.com>
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Date: Fri, 24 May 2019 18:23:38 +0200
In-Reply-To: <CAAt2M1_PKnJ5tR3VHgUg-=ibNVVp-Yocqa9KeUQhVj0X2PstGA@mail.gmail.com>
To: Natanael <natanael.l@gmail.com>
References: <CAD5xwhgHyR5qdd09ikvA_vgepj4o+Aqb0JA_T6FuqX56ZNe1RQ@mail.gmail.com>
	<42F53D61-BAAE-464F-BB0D-4D0CDC554D9A@gmail.com>
	<CAPg+sBged=ivVLj9tAM6zZdvWdYnG5pj4gozac5EupFPLtwyfA@mail.gmail.com>
	<CAAt2M1_PKnJ5tR3VHgUg-=ibNVVp-Yocqa9KeUQhVj0X2PstGA@mail.gmail.com>
Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>,
	Pieter Wuille <pieter.wuille@gmail.com>
Subject: Re: [bitcoin-dev] OP_DIFFICULTY to enable difficulty hedges (bets)
 without an oracle and 3rd party.
Precedence: list


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yes, log2work is already computed and would be a strictly increasing =
value, like time. Thank you for this suggestion. I think attempting an =
implementation will give further clues it this more suitable to express =
the same.

Tamas Blummer

> On May 24, 2019, at 10:36, Natanael <natanael.l@gmail.com> wrote:
>=20
> On Thu, May 23, 2019 at 9:58 PM Pieter Wuille via bitcoin-dev =
<bitcoin-dev@lists.linuxfoundation.org =
<mailto:bitcoin-dev@lists.linuxfoundation.org>> wrote:
> If the difficulty can be directly observed by the script language, you
> would need to re-evaluate all scripts in unconfirmed transactions
> whenever the difficulty changes. This complicates implementation of
> mempools, but it also makes reasoning about validity of (chains of)
> unconfirmed transactions harder, as an unconfirmed predecessor may
> have conditions that change over time.
>=20
> To deal with potentially wildly varying difficulty, could the value =
exposed be the sum of accumulated PoW, or in other words the sum of each =
block's difficulty value in the entire chain? This should be a value =
that will only rise unless a reorg happens after a difficulty drop =
happens (only likely to be the result of users manually blacklisting an =
otherwise valid block that is several blocks back in the chain).
>=20
> This mimics the effect of the block number which only grows. So if =
you're starting at time A with difficulty X, then you'd estimate what =
you think the accumulated PoW ought to be at time B with expected =
difficulty Y (as compared to the current value at time A), and put that =
value into the script.


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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; -webkit-line-break: after-white-space;" =
class=3D""><div class=3D"">yes, log2work is already computed and would =
be a strictly increasing value, like time. Thank you for this =
suggestion. I think attempting an implementation will give further clues =
it this more suitable to express the same.</div><div class=3D""><br =
class=3D""></div><div class=3D"">Tamas Blummer</div><br =
class=3D""><div><blockquote type=3D"cite" class=3D""><div class=3D"">On =
May 24, 2019, at 10:36, Natanael &lt;<a =
href=3D"mailto:natanael.l@gmail.com" =
class=3D"">natanael.l@gmail.com</a>&gt; wrote:</div><br =
class=3D"Apple-interchange-newline"><div class=3D""><div dir=3D"ltr" =
class=3D""><div dir=3D"ltr" class=3D"">On Thu, May 23, 2019 at 9:58 PM =
Pieter Wuille via bitcoin-dev &lt;<a =
href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" =
class=3D"">bitcoin-dev@lists.linuxfoundation.org</a>&gt; wrote:<br =
class=3D""></div><div class=3D"gmail_quote"><blockquote =
class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px =
solid rgb(204,204,204);padding-left:1ex">If the difficulty can be =
directly observed by the script language, you<br class=3D"">
would need to re-evaluate all scripts in unconfirmed transactions<br =
class=3D"">
whenever the difficulty changes. This complicates implementation of<br =
class=3D"">
mempools, but it also makes reasoning about validity of (chains of)<br =
class=3D"">
unconfirmed transactions harder, as an unconfirmed predecessor may<br =
class=3D"">
have conditions that change over time.</blockquote><div class=3D""><br =
class=3D""></div><div class=3D"">To deal with potentially wildly varying =
difficulty, could the value exposed be the sum of accumulated PoW, or in =
other words the sum of each block's difficulty value in the entire =
chain? This should be a value that will only rise unless a reorg happens =
after a difficulty drop happens (only likely to be the result of users =
manually blacklisting an otherwise valid block that is several blocks =
back in the chain).</div><div class=3D""><br class=3D""></div><div =
class=3D"">This mimics the effect of the block number which only grows. =
So if you're starting at time A with difficulty X, then you'd estimate =
what you think the accumulated PoW ought to be at time B with expected =
difficulty Y (as compared to the current value at time A), and put that =
value into the script.</div></div></div>
</div></blockquote></div><br class=3D""></body></html>=

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