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From: Salvatore Ingala <salvatore.ingala@gmail.com>
Date: Mon, 28 Jun 2021 12:03:42 +0200
Message-ID: <CAMhCMoF7N4BuXDz1cSDBLi5zH8c06uZ3T3gc750azFH3JagcNw@mail.gmail.com>
To: Andrew Chow <achow101-lists@achow101.com>, 
 Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Content-Type: multipart/alternative; boundary="000000000000599c7d05c5d09b60"
Subject: Re: [bitcoin-dev] Taproot Fields for PSBT
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Hi Andrew,

I just have a small suggestion on this proposal.

On Tue, 22 Jun 2021 at 23:29, Andrew Chow via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> | Taproot Leaf Script
> | <tt>PSBT_IN_TAP_LEAF_SCRIPT = 0x15</tt>
> | <tt><control block></tt>
> | The control block for this leaf as specified in BIP 341. The control
> block contains the merkle tree path to this leaf.
> | <tt><script> <8-bit uint></tt>
> | The script for this leaf as would be provided in the witness stack
> followed by the single byte leaf version.
>

So far, all the defined PSBT types had a relatively short keydata (not much
bigger than a couple of pubkeys).
I think that is a desirable property to keep, as it is often a reasonable
assumption that dictionary keys are not very large.
The control block as per BIP 341 can be up to 33 + 32*128 = 4129 bytes long.

Perhaps it would be better to split this into PSBT_IN_TAP_LEAF_SCRIPT
and PSBT_IN_TAP_LEAF_CONTROL_BLOCK (both with no keydata)?

Best,
Salvatore Ingala

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<div dir=3D"ltr"><div dir=3D"ltr">Hi Andrew,<div><br></div><div>I just have=
 a small suggestion on this proposal.</div></div><br><div class=3D"gmail_qu=
ote"><div dir=3D"ltr" class=3D"gmail_attr">On Tue, 22 Jun 2021 at 23:29, An=
drew Chow via bitcoin-dev &lt;<a href=3D"mailto:bitcoin-dev@lists.linuxfoun=
dation.org">bitcoin-dev@lists.linuxfoundation.org</a>&gt; wrote:<br></div><=
blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-l=
eft:1px solid rgb(204,204,204);padding-left:1ex">| Taproot Leaf Script<br>
| &lt;tt&gt;PSBT_IN_TAP_LEAF_SCRIPT =3D 0x15&lt;/tt&gt;<br>
| &lt;tt&gt;&lt;control block&gt;&lt;/tt&gt;<br>
| The control block for this leaf as specified in BIP 341. The control<br>
block contains the merkle tree path to this leaf.<br>
| &lt;tt&gt;&lt;script&gt; &lt;8-bit uint&gt;&lt;/tt&gt;<br>
| The script for this leaf as would be provided in the witness stack<br>
followed by the single byte leaf version.<br></blockquote><div><br></div><d=
iv>So far, all the defined PSBT types had a relatively short keydata (not m=
uch bigger than a couple of pubkeys).</div><div>I think that is a desirable=
 property to keep, as it is often a reasonable assumption that dictionary k=
eys are not very large.</div><div>The control=C2=A0block as per BIP 341 can=
 be up to 33 + 32*128 =3D 4129 bytes long.<br></div><div><br></div><div>Per=
haps it would be better to split this into PSBT_IN_TAP_LEAF_SCRIPT and=C2=
=A0PSBT_IN_TAP_LEAF_CONTROL_BLOCK (both with no keydata)?</div><div><br></d=
iv><div>Best,</div><div>Salvatore Ingala</div><div><br></div></div></div>

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