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From: Riccardo Casatta <riccardo.casatta@gmail.com>
Date: Fri, 17 Sep 2021 09:07:48 +0200
Message-ID: <CADabwBB4jmwqyJAqfghWTGLiCHFYXset5ZvKB36Q2FkMomJCtQ@mail.gmail.com>
To: Giacomo Caironi <giacomo.caironi@gmail.com>, 
 Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Content-Type: multipart/alternative; boundary="0000000000006b9a7f05cc2b973f"
Subject: Re: [bitcoin-dev] Test cases for Taproot signature message
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Hi Giacomo,

I wrote the rust implementation of bitcoin signature messages and to
double-check I created some test vectors you can see at
https://github.com/rust-bitcoin/rust-bitcoin/blob/b7f984972ad6cb4942827c2b7c401f590588cdcf/src/util/sighash.rs#L689-L799.
These vectors have been created printing intermediate results from
https://github.com/bitcoin/bitcoin/blob/6401de0133e32a641ed9e78a85b3aa337c75d190/test/functional/feature_taproot.py

Il giorno gio 16 set 2021 alle ore 23:40 Giacomo Caironi via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> ha scritto:

> Hi,
> recently I have worked on a python implementation of bitcoin signature
> messages, and I have found that there was way better documentation about
> Segwit signature message than Taproot.
>
> 1) Segwit signature message got its own BIP, completed with test cases
> regarding only that specific function; Taproot on the other hand has the
> signature message function defined in BIP 341 and the test vectors in a
> different BIP (341). This is confusing. Shouldn't we create a different BIP
> only for Taproot signature message exactly like Segwit?
>
> 2) The test vectors for Taproot have no documentation and, most
> importantly, they are not atomic, in the sense that they do not target a
> specific part of the taproot code but all of it. This may not be a very big
> problem, but for signature verification it is. Because there are hashes
> involved, we can't really debug why a signature message doesn't pass
> validation, either it is valid or it is not. BIP 143 in this case is really
> good, because it provides hash preimages, so it is possible to debug the
> function and see where something went wrong. Because of this, writing the
> Segwit signature hash function took a fraction of the time compared to
> Taproot.
>
> If this idea is accepted I will be more than happy to write the test cases
> for Taproot.
>
> BTW this is the first time I contribute to Bitcoin, let me know if I was
> rude or did something wrong. Moreover english is not my first language, so
> I apologize if I wrote something awful above
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>


-- 
Riccardo Casatta - @RCasatta <https://twitter.com/RCasatta>

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<div dir=3D"ltr"><div class=3D"gmail_default" style=3D"font-size:small">Hi =
Giacomo,</div><div class=3D"gmail_default" style=3D"font-size:small"><br></=
div><div class=3D"gmail_default" style=3D"font-size:small">I wrote the rust=
 implementation of bitcoin signature messages and to double-check I created=
 some test vectors you can see at=C2=A0<a href=3D"https://github.com/rust-b=
itcoin/rust-bitcoin/blob/b7f984972ad6cb4942827c2b7c401f590588cdcf/src/util/=
sighash.rs#L689-L799">https://github.com/rust-bitcoin/rust-bitcoin/blob/b7f=
984972ad6cb4942827c2b7c401f590588cdcf/src/util/sighash.rs#L689-L799</a>. Th=
ese vectors have been created printing intermediate results from <a href=3D=
"https://github.com/bitcoin/bitcoin/blob/6401de0133e32a641ed9e78a85b3aa337c=
75d190/test/functional/feature_taproot.py">https://github.com/bitcoin/bitco=
in/blob/6401de0133e32a641ed9e78a85b3aa337c75d190/test/functional/feature_ta=
proot.py</a></div></div><br><div class=3D"gmail_quote"><div dir=3D"ltr" cla=
ss=3D"gmail_attr">Il giorno gio 16 set 2021 alle ore 23:40 Giacomo Caironi =
via bitcoin-dev &lt;<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org=
">bitcoin-dev@lists.linuxfoundation.org</a>&gt; ha scritto:<br></div><block=
quote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1=
px solid rgb(204,204,204);padding-left:1ex"><div dir=3D"ltr">Hi,=C2=A0<div>=
recently I have worked on a python implementation of bitcoin signature mess=
ages, and I have found that there was way better documentation about Segwit=
 signature message than Taproot.</div><div><br></div><div>1) Segwit signatu=
re message got its own BIP, completed with test cases regarding only that s=
pecific function; Taproot on the other hand has the signature message funct=
ion defined in BIP 341 and the test vectors in a different BIP (341). This =
is confusing. Shouldn&#39;t we create a different BIP only for Taproot sign=
ature message exactly like Segwit?</div><div><br></div><div>2) The test vec=
tors for Taproot have no documentation and, most importantly, they are not =
atomic, in the sense that they do not target a specific part of the taproot=
 code but all of it. This may not be a very big problem, but for signature =
verification it is. Because there are hashes involved, we can&#39;t really =
debug why a signature message doesn&#39;t pass validation, either it is val=
id or it is not. BIP 143 in this case is really good, because it provides h=
ash preimages, so it is possible to debug the function and see where someth=
ing went wrong. Because of this, writing the Segwit signature hash function=
 took a fraction of the time compared to Taproot.</div><div><br></div><div>=
If this idea is accepted I will be more than happy to write the test cases =
for Taproot.</div><div><br></div><div>BTW this is the first time I contribu=
te to Bitcoin, let me know if I was rude or did something wrong. Moreover e=
nglish is not my first language, so I apologize if I wrote something awful =
above</div></div>
_______________________________________________<br>
bitcoin-dev mailing list<br>
<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" target=3D"_blank">=
bitcoin-dev@lists.linuxfoundation.org</a><br>
<a href=3D"https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev" =
rel=3D"noreferrer" target=3D"_blank">https://lists.linuxfoundation.org/mail=
man/listinfo/bitcoin-dev</a><br>
</blockquote></div><br clear=3D"all"><div><br></div>-- <br><div dir=3D"ltr"=
 class=3D"gmail_signature"><div dir=3D"ltr">Riccardo Casatta - <a href=3D"h=
ttps://twitter.com/RCasatta" target=3D"_blank">@RCasatta</a></div></div>

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