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	<E8BB95A5-09B3-443C-B197-29DA3C4767D8@xbt.hk>
From: "Russell O'Connor" <roconnor@blockstream.io>
Date: Thu, 3 Nov 2016 00:19:48 -0400
Message-ID: <CAMZUoKmnkk=q7GkkvA+Q4-r64JCQ+kPRPdoEN8bnAwd2YGMH+Q@mail.gmail.com>
To: Johnson Lau <jl2012@xbt.hk>
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Cc: bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Implementing Covenants with
	OP_CHECKSIGFROMSTACKVERIFY
Precedence: list

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Right.  There are minor trade-offs to be made with regards to that design
point of OP_CHECKSIGFROMSTACKVERIFY.  Fortunately this covenant
construction isn't sensitive to that choice and can be made to work with
either implementation of OP_CHECKSIGFROMSTACKVERIFY.

On Wed, Nov 2, 2016 at 11:35 PM, Johnson Lau <jl2012@xbt.hk> wrote:

> Interesting. I have implemented OP_CHECKSIGFROMSTACKVERIFY in a different
> way from the Elements. Instead of hashing the data on stack, I directly put
> the 32 byte hash to the stack. This should be more flexible as not every
> system are using double-SHA256
>
> https://github.com/jl2012/bitcoin/commits/mast_v3_master
>
>
> On 3 Nov 2016, at 01:30, Russell O'Connor via bitcoin-dev <
> bitcoin-dev@lists.linuxfoundation.org> wrote:
>
> Hi all,
>
> It is possible to implement covenants using two script extensions: OP_CAT
> and OP_CHECKSIGFROMSTACKVERIFY.  Both of these op codes are already
> available in the Elements Alpha sidechain, so it is possible to construct
> covenants in Elements Alpha today.  I have detailed how the construction
> works in a blog post at <https://blockstream.com/2016/
> 11/02/covenants-in-elements-alpha.html>.  As an example, I've constructed
> scripts for the Moeser-Eyal-Sirer vault.
>
> I'm interested in collecting and implementing other useful covenants, so
> if people have ideas, please post them.
>
> If there are any questions, I'd be happy to answer.
>
> --
> Russell O'Connor
> _______________________________________________
> 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">Right.=C2=A0 There are minor trade-offs to be made with re=
gards to that design point of OP_<wbr>CHECKSIGFROMSTACKVERIFY.=C2=A0 Fortun=
ately this covenant construction isn&#39;t sensitive to that choice and can=
 be made to work with either implementation of OP_<wbr>CHECKSIGFROMSTACKVER=
IFY.<br><div><div class=3D"gmail_extra"><br><div class=3D"gmail_quote">On W=
ed, Nov 2, 2016 at 11:35 PM, Johnson Lau <span dir=3D"ltr">&lt;<a href=3D"m=
ailto:jl2012@xbt.hk" target=3D"_blank">jl2012@xbt.hk</a>&gt;</span> wrote:<=
br><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;bord=
er-left:1px solid rgb(204,204,204);padding-left:1ex"><div style=3D"overflow=
-wrap: break-word;"><div>Interesting. I have implemented=C2=A0OP_<wbr>CHECK=
SIGFROMSTACKVERIFY in a different way from the Elements. Instead of hashing=
 the data on stack, I directly put the 32 byte hash to the stack. This shou=
ld be more flexible as not every system are using double-SHA256</div><div><=
br></div><div><a href=3D"https://github.com/jl2012/bitcoin/commits/mast_v3_=
master" target=3D"_blank">https://github.com/jl2012/<wbr>bitcoin/commits/ma=
st_v3_master</a></div><div><br></div><br><div><blockquote type=3D"cite"><di=
v><div class=3D"gmail-h5"><div>On 3 Nov 2016, at 01:30, Russell O&#39;Conno=
r via bitcoin-dev &lt;<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.o=
rg" target=3D"_blank">bitcoin-dev@lists.<wbr>linuxfoundation.org</a>&gt; wr=
ote:</div><br class=3D"gmail-m_3266083758070358714Apple-interchange-newline=
"></div></div><div><div><div class=3D"gmail-h5"><div dir=3D"ltr">Hi all,<br=
><br>It is possible to implement covenants using two script extensions: OP_=
CAT and OP_CHECKSIGFROMSTACKVERIFY.=C2=A0 Both of these op codes are alread=
y available in the Elements Alpha sidechain, so it is possible to construct=
 covenants in Elements Alpha today.=C2=A0 I have detailed how the construct=
ion works in a blog post at &lt;<a href=3D"https://blockstream.com/2016/11/=
02/covenants-in-elements-alpha.html" target=3D"_blank">https://blockstream.=
com/2016/<wbr>11/02/covenants-in-elements-<wbr>alpha.html</a>&gt;.=C2=A0 As=
 an example, I&#39;ve constructed scripts for the Moeser-Eyal-Sirer vault.<=
br><br>I&#39;m interested in collecting and implementing other useful coven=
ants, so if people have ideas, please post them.<br><br>If there are any qu=
estions, I&#39;d be happy to answer.=C2=A0 <br><br>-- <br>Russell O&#39;Con=
nor<br></div></div></div>
______________________________<wbr>_________________<br>bitcoin-dev mailing=
 list<br><a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" target=3D=
"_blank">bitcoin-dev@lists.<wbr>linuxfoundation.org</a><br><a href=3D"https=
://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev" target=3D"_blank=
">https://lists.linuxfoundation.<wbr>org/mailman/listinfo/bitcoin-<wbr>dev<=
/a><br></div></blockquote></div><br></div></blockquote></div><br></div></di=
v></div>

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