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From: Mark Friedenbach <mark@friedenbach.org>
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Date: Mon, 27 Nov 2017 13:06:35 -0800
In-Reply-To: <56ca1248-6427-46f7-1645-84349cc8facc@mattcorallo.com>
To: Matt Corallo <lf-lists@mattcorallo.com>
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Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Making OP_CODESEPARATOR and FindAndDelete in
 non-segwit scripts non-standard
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It is relevant to note that BIP 117 makes an insecure form of =
CODESEPARATOR delegation possible, which could be made secure if some =
sort of CHECKSIGFROMSTACK opcode is added at a later point in time. It =
is not IMHO a very elegant way to achieve delegation, however, so I hope =
that one way or another this could be resolved quickly so it doesn=E2=80=99=
t hold up either one of those valuable additions.

I have no objections to making them nonstandard, or even to make them =
invalid if someone with a better grasp of history can attest that =
CODESEPARATOR was known to be entirely useless before the introduction =
of P2SH=E2=80=94not the same as saying it was useless, but that it was =
widely known to not accomplish what a early-days script author might =
think it was doing=E2=80=94and the UTXO set contains no scriptPubKeys =
making use of the opcode, even from the early days. Although a small =
handful could be special cased, if they exist.

> On Nov 27, 2017, at 8:33 AM, Matt Corallo <lf-lists@mattcorallo.com> =
wrote:
>=20
> I strongly disagree here - we don't only soft-fork out transactions =
that
> are "fundamentally insecure", that would be significantly too
> restrictive. We have generally been willing to soft-fork out things
> which clearly fall outside of best-practices, especially rather
> "useless" fields in the protocol eg soft-forking behavior into =
OP_NOPs,
> soft-forking behavior into nSequence, etc.
>=20
> As a part of setting clear best-practices, making things non-standard =
is
> the obvious step, though there has been active discussion of
> soft-forking out FindAndDelete and OP_CODESEPARATOR for years now. I
> obviously do not claim that we should be proposing a soft-fork to
> blacklist FindAndDelete and OP_CODESEPARATOR usage any time soon, and
> assume that it would take at least a year or three from when it was =
made
> non-standard to when a soft-fork to finally remove them was proposed.
> This should be more than sufficient time for folks using such weird =
(and
> largely useless) parts of the protocol to object, which should be
> sufficient to reconsider such a soft-fork.
>=20
> Independently, making them non-standard is a good change on its own, =
and
> if nothing else should better inform discussion about the possibility =
of
> anyone using these things.
>=20
> Matt
>=20
> On 11/15/17 14:54, Mark Friedenbach via bitcoin-dev wrote:
>> As good of an idea as it may or may not be to remove this feature =
from
>> the code base, actually doing so would be crossing a boundary that we
>> have not previously been willing to do except under extraordinary
>> duress. The nature of bitcoin is such that we do not know and cannot
>> know what transactions exist out there pre-signed and making use of
>> these features.
>>=20
>> It may be a good idea to make these features non standard to further
>> discourage their use, but I object to doing so with the justification =
of
>> eventually disabling them for all transactions. Taking that step has =
the
>> potential of destroying value and is something that we have only done =
in
>> the past either because we didn=E2=80=99t understand forks and best =
practices
>> very well, or because the features (now disabled) were fundamentally
>> insecure and resulted in other people=E2=80=99s coins being =
vulnerable. This
>> latter concern does not apply here as far as I=E2=80=99m aware.
>>=20
>> On Nov 15, 2017, at 8:02 AM, Johnson Lau via bitcoin-dev
>> <bitcoin-dev@lists.linuxfoundation.org
>> <mailto:bitcoin-dev@lists.linuxfoundation.org =
<mailto:bitcoin-dev@lists.linuxfoundation.org>>> wrote:
>>=20
>>> In https://github.com/bitcoin/bitcoin/pull/11423 I propose to
>>> make OP_CODESEPARATOR and FindAndDelete in non-segwit scripts =
non-standard
>>>=20
>>> I think FindAndDelete() is one of the most useless and complicated
>>> functions in the script language. It is omitted from segwit =
(BIP143),
>>> but we still need to support it in non-segwit scripts. Actually,
>>> FindAndDelete() would only be triggered in some weird edge cases =
like
>>> using out-of-range SIGHASH_SINGLE.
>>>=20
>>> Non-segwit scripts also use a FindAndDelete()-like function to =
remove
>>> OP_CODESEPARATOR from scriptCode. Note that in BIP143, only executed
>>> OP_CODESEPARATOR are removed so it doesn=E2=80=99t have the
>>> FindAndDelete()-like function. OP_CODESEPARATOR in segwit scripts =
are
>>> useful for Tumblebit so it is not disabled in this proposal
>>>=20
>>> By disabling both, it guarantees that scriptCode serialized inside
>>> SignatureHash() must be constant
>>>=20
>>> If we use a softfork to remove FindAndDelete() and OP_CODESEPARATOR
>>> from non-segwit scripts, we could completely remove FindAndDelete()
>>> from the consensus code later by whitelisting all blocks before the
>>> softfork block. The first step is to make them non-standard in the
>>> next release.
>>>=20
>>>=20
>>> =20
>>> _______________________________________________
>>> bitcoin-dev mailing list
>>> bitcoin-dev@lists.linuxfoundation.org =
<mailto:bitcoin-dev@lists.linuxfoundation.org>
>>> <mailto:bitcoin-dev@lists.linuxfoundation.org =
<mailto:bitcoin-dev@lists.linuxfoundation.org>>
>>> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev =
<https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev>
>>=20
>>=20
>> _______________________________________________
>> bitcoin-dev mailing list
>> bitcoin-dev@lists.linuxfoundation.org =
<mailto:bitcoin-dev@lists.linuxfoundation.org>
>> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev =
<https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev>

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<html><head><meta http-equiv=3D"Content-Type" content=3D"text/html; =
charset=3Dutf-8"></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; line-break: after-white-space;" class=3D"">It =
is relevant to note that BIP 117 makes an insecure form of CODESEPARATOR =
delegation possible, which could be made secure if some sort of =
CHECKSIGFROMSTACK opcode is added at a later point in time. It is not =
IMHO a very elegant way to achieve delegation, however, so I hope that =
one way or another this could be resolved quickly so it doesn=E2=80=99t =
hold up either one of those valuable additions.<div class=3D""><br =
class=3D""></div><div class=3D"">I have no objections to making them =
nonstandard, or even to make them invalid if someone with a better grasp =
of history can attest that CODESEPARATOR was known to be entirely =
useless before the introduction of P2SH=E2=80=94not the same as saying =
it was useless, but that it was widely known to not accomplish what a =
early-days script author might think it was doing=E2=80=94and the UTXO =
set contains no scriptPubKeys making use of the opcode, even from the =
early days. Although a small handful could be special cased, if they =
exist.</div><div class=3D""><div><br class=3D""><blockquote type=3D"cite" =
class=3D""><div class=3D"">On Nov 27, 2017, at 8:33 AM, Matt Corallo =
&lt;<a href=3D"mailto:lf-lists@mattcorallo.com" =
class=3D"">lf-lists@mattcorallo.com</a>&gt; wrote:</div><br =
class=3D"Apple-interchange-newline"><div class=3D""><span =
style=3D"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; float: none; =
display: inline !important;" class=3D"">I strongly disagree here - we =
don't only soft-fork out transactions that</span><br style=3D"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;" class=3D""><span =
style=3D"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; float: none; =
display: inline !important;" class=3D"">are "fundamentally insecure", =
that would be significantly too</span><br style=3D"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;" class=3D""><span =
style=3D"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; float: none; =
display: inline !important;" class=3D"">restrictive. We have generally =
been willing to soft-fork out things</span><br style=3D"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;" class=3D""><span =
style=3D"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; float: none; =
display: inline !important;" class=3D"">which clearly fall outside of =
best-practices, especially rather</span><br style=3D"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;" class=3D""><span =
style=3D"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; float: none; =
display: inline !important;" class=3D"">"useless" fields in the protocol =
eg soft-forking behavior into OP_NOPs,</span><br style=3D"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;" class=3D""><span =
style=3D"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; float: none; =
display: inline !important;" class=3D"">soft-forking behavior into =
nSequence, etc.</span><br style=3D"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;" class=3D""><br style=3D"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;" class=3D""><span =
style=3D"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; float: none; =
display: inline !important;" class=3D"">As a part of setting clear =
best-practices, making things non-standard is</span><br =
style=3D"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;" =
class=3D""><span style=3D"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; float: none; display: inline =
!important;" class=3D"">the obvious step, though there has been active =
discussion of</span><br style=3D"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;" class=3D""><span style=3D"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; float: none; display: =
inline !important;" class=3D"">soft-forking out FindAndDelete and =
OP_CODESEPARATOR for years now. I</span><br style=3D"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;" class=3D""><span =
style=3D"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; float: none; =
display: inline !important;" class=3D"">obviously do not claim that we =
should be proposing a soft-fork to</span><br style=3D"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;" class=3D""><span =
style=3D"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; float: none; =
display: inline !important;" class=3D"">blacklist FindAndDelete and =
OP_CODESEPARATOR usage any time soon, and</span><br style=3D"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;" class=3D""><span =
style=3D"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; float: none; =
display: inline !important;" class=3D"">assume that it would take at =
least a year or three from when it was made</span><br =
style=3D"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;" =
class=3D""><span style=3D"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; float: none; display: inline =
!important;" class=3D"">non-standard to when a soft-fork to finally =
remove them was proposed.</span><br style=3D"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;" class=3D""><span =
style=3D"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; float: none; =
display: inline !important;" class=3D"">This should be more than =
sufficient time for folks using such weird (and</span><br =
style=3D"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;" =
class=3D""><span style=3D"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; float: none; display: inline =
!important;" class=3D"">largely useless) parts of the protocol to =
object, which should be</span><br style=3D"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;" class=3D""><span =
style=3D"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; float: none; =
display: inline !important;" class=3D"">sufficient to reconsider such a =
soft-fork.</span><br style=3D"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;" class=3D""><br style=3D"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;" class=3D""><span =
style=3D"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; float: none; =
display: inline !important;" class=3D"">Independently, making them =
non-standard is a good change on its own, and</span><br =
style=3D"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;" =
class=3D""><span style=3D"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; float: none; display: inline =
!important;" class=3D"">if nothing else should better inform discussion =
about the possibility of</span><br style=3D"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;" class=3D""><span =
style=3D"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; float: none; =
display: inline !important;" class=3D"">anyone using these =
things.</span><br style=3D"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;" class=3D""><br style=3D"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;" class=3D""><span =
style=3D"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; float: none; =
display: inline !important;" class=3D"">Matt</span><br =
style=3D"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;" class=3D""><br=
 style=3D"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;" =
class=3D""><span style=3D"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; float: none; display: inline =
!important;" class=3D"">On 11/15/17 14:54, Mark Friedenbach via =
bitcoin-dev wrote:</span><br style=3D"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;" class=3D""><blockquote type=3D"cite" =
style=3D"font-family: Helvetica; font-size: 12px; font-style: normal; =
font-variant-caps: normal; font-weight: normal; letter-spacing: normal; =
orphans: auto; text-align: start; text-indent: 0px; text-transform: =
none; white-space: normal; widows: auto; word-spacing: 0px; =
-webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" =
class=3D"">As good of an idea as it may or may not be to remove this =
feature from<br class=3D"">the code base, actually doing so&nbsp;would =
be crossing a boundary that we<br class=3D"">have not previously been =
willing to do except under extraordinary<br class=3D"">duress. The =
nature of bitcoin is such that we do not know and cannot<br =
class=3D"">know what transactions exist out there pre-signed and making =
use of<br class=3D"">these features.<br class=3D""><br class=3D"">It may =
be a good idea to make these features non standard to further<br =
class=3D"">discourage their use, but I object to doing so with the =
justification of<br class=3D"">eventually disabling them for all =
transactions. Taking that step has the<br class=3D"">potential of =
destroying value and is something that we have only done in<br =
class=3D"">the past either because we didn=E2=80=99t understand forks =
and best practices<br class=3D"">very well, or because the features (now =
disabled) were fundamentally<br class=3D"">insecure and resulted in =
other people=E2=80=99s coins being vulnerable. This<br class=3D"">latter =
concern does not apply here as far as I=E2=80=99m aware.<br class=3D""><br=
 class=3D"">On Nov 15, 2017, at 8:02 AM, Johnson Lau via bitcoin-dev<br =
class=3D"">&lt;<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" =
class=3D"">bitcoin-dev@lists.linuxfoundation.org</a><br class=3D"">&lt;<a =
href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" =
class=3D"">mailto:bitcoin-dev@lists.linuxfoundation.org</a>&gt;&gt; =
wrote:<br class=3D""><br class=3D""><blockquote type=3D"cite" =
class=3D"">In&nbsp;<a =
href=3D"https://github.com/bitcoin/bitcoin/pull/11423" =
class=3D"">https://github.com/bitcoin/bitcoin/pull/11423</a>&nbsp;I =
propose to<br class=3D"">make&nbsp;OP_CODESEPARATOR and FindAndDelete in =
non-segwit scripts non-standard<br class=3D""><br class=3D"">I think =
FindAndDelete() is one of the most useless and complicated<br =
class=3D"">functions in the script language. It is omitted from segwit =
(BIP143),<br class=3D"">but we still need to support it in non-segwit =
scripts. Actually,<br class=3D"">FindAndDelete() would only be triggered =
in some weird edge cases like<br class=3D"">using out-of-range =
SIGHASH_SINGLE.<br class=3D""><br class=3D"">Non-segwit scripts also use =
a FindAndDelete()-like function to remove<br class=3D"">OP_CODESEPARATOR =
from scriptCode. Note that in BIP143, only executed<br =
class=3D"">OP_CODESEPARATOR are removed so it doesn=E2=80=99t have =
the<br class=3D"">FindAndDelete()-like function. OP_CODESEPARATOR in =
segwit scripts are<br class=3D"">useful for Tumblebit so it is not =
disabled in this proposal<br class=3D""><br class=3D"">By disabling =
both, it guarantees that scriptCode serialized inside<br =
class=3D"">SignatureHash() must be constant<br class=3D""><br =
class=3D"">If we use a softfork to remove FindAndDelete() and =
OP_CODESEPARATOR<br class=3D"">from non-segwit scripts, we could =
completely remove FindAndDelete()<br class=3D"">from the consensus code =
later by whitelisting all blocks before the<br class=3D"">softfork =
block. The first step is to make them non-standard in the<br =
class=3D"">next release.<br class=3D""><br class=3D""><br =
class=3D"">&nbsp;<br =
class=3D"">_______________________________________________<br =
class=3D"">bitcoin-dev mailing list<br class=3D""><a =
href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" =
class=3D"">bitcoin-dev@lists.linuxfoundation.org</a><br class=3D"">&lt;<a =
href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" =
class=3D"">mailto:bitcoin-dev@lists.linuxfoundation.org</a>&gt;<br =
class=3D""><a =
href=3D"https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev" =
class=3D"">https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev<=
/a><br class=3D""></blockquote><br class=3D""><br =
class=3D"">_______________________________________________<br =
class=3D"">bitcoin-dev mailing list<br class=3D""><a =
href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" =
class=3D"">bitcoin-dev@lists.linuxfoundation.org</a><br class=3D""><a =
href=3D"https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev" =
class=3D"">https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev<=
/a></blockquote></div></blockquote></div><br =
class=3D""></div></body></html>=

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