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Date: Tue, 8 Jul 2025 07:45:30 -0700 (PDT)
From: "aaron.recompile" <aaron.recompile@gmail.com>
To: Bitcoin Development Mailing List <bitcoindev@googlegroups.com>
Message-Id: <d4f04a90-9842-4260-8e7b-79ed2bc00adan@googlegroups.com>
Subject: [bitcoindev] [taproot][script] 4-leaf Taproot Merkle Tree in Python:
testnet implementation + control block analysis
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------=_Part_555563_1234549647.1751985930931
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Hi all,
I'm Aaron Zhang, an independent developer focused on Bitcoin script=20
engineering and Taproot experimentation.
I=E2=80=99d like to share a hands-on project involving a fully constructed =
4-leaf=20
Taproot Merkle tree in Python, with testnet-validated spending transactions=
=20
and in-depth analysis of control block internals.
This work features:
- Construction of a *Taproot address with 4 distinct script leaves*:
1. `OP_SHA256` + `OP_EQUAL` hashlock
2. 2-of-2 `OP_CHECKMULTISIG`
3. `OP_CSV` + `OP_CHECKSIG`
4. `OP_CHECKSIG`
- A total of *five spending paths*, including four script path spends and=
=20
one key path spend, all confirmed through on-chain transactions on Bitcoin=
=20
testnet.
- Merkle tree construction and Taproot output key tweaking (internal key +=
=20
script tree root), followed by a **byte-by-byte breakdown of the control=20
blocks**, including:
- Control byte (leaf version + parity)
- Internal public key
- Ordered Merkle sibling hashes
- *Code-level analysis and experimental validation of how these control=20
blocks* are constructed and verified against the Taproot output, based on=
=20
actual testnet spends.
- *Witness stack inspection and visualization of script execution*, showing=
=20
the actual runtime behavior for each script path.
Resources:
*- Part 1: 4-leaf tree construction and testnet validation * =20
https://medium.com/@aaron.recompile/building-a-4-leaf-taproot-tree-in-pytho=
n-the-first-complete-implementation-on-bitcoin-testnet-c8b66c331f29
*- Part 2: Control block structure and stack visualization * =20
https://medium.com/@aaron.recompile/taproot-control-block-deep-analysis-sta=
ck-execution-visualization-5ff10f98032c
- GitHub repo with code, testnet transactions, and diagrams =20
=20
https://github.com/btcstudy/btcstudy.github.io/tree/main/Not-Just-Hodling:b=
itcoin-script-Engineering/demo3_taproot_4leaf
This project aims to provide a fully verifiable and pedagogical example of=
=20
non-trivial Taproot path spends, helping developers better understand=20
script trees, control blocks, and Tapscript execution through practical=20
experimentation.
I=E2=80=99d be happy to receive any feedback or discussion around:
- Control block design and merkle path optimization
- Spend path visibility and privacy tradeoffs
- Tooling for visualizing script-path execution and verification
Thanks and best regards, =20
Aaron Zhang =20
[@aaron.recompile](https://medium.com/@aaron.recompile) =20
GitHub: https://github.com/btcstudy
--=20
You received this message because you are subscribed to the Google Groups "=
Bitcoin Development Mailing List" group.
To unsubscribe from this group and stop receiving emails from it, send an e=
mail to bitcoindev+unsubscribe@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/bitcoindev/=
d4f04a90-9842-4260-8e7b-79ed2bc00adan%40googlegroups.com.
------=_Part_555563_1234549647.1751985930931
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Hi all,<br /><br />I'm Aaron Zhang, an independent developer focused on Bit=
coin script engineering and Taproot experimentation.<br /><br />I=E2=80=99d=
like to share a hands-on project involving a fully constructed 4-leaf Tapr=
oot Merkle tree in Python, with testnet-validated spending transactions and=
in-depth analysis of control block internals.<br /><br />This work feature=
s:<br /><br />- Construction of a <b>Taproot address with 4 distinct script=
leaves</b>:<br />=C2=A0 =C2=A0 1. `OP_SHA256` + `OP_EQUAL` hashlock<br />=
=C2=A0 =C2=A0 2. 2-of-2 `OP_CHECKMULTISIG`<br />=C2=A0 =C2=A0 3. `OP_CSV` +=
`OP_CHECKSIG`<br />=C2=A0 =C2=A0 4. `OP_CHECKSIG`<br /><br />- A total of =
<b>five spending paths</b>, including four script path spends and one key p=
ath spend, all confirmed through on-chain transactions on Bitcoin testnet.<=
br /><br />- Merkle tree construction and Taproot output key tweaking (inte=
rnal key + script tree root), followed by a **byte-by-byte breakdown of the=
control blocks**, including:<br />=C2=A0 =C2=A0 - Control byte (leaf versi=
on + parity)<br />=C2=A0 =C2=A0 - Internal public key<br />=C2=A0 =C2=A0 - =
Ordered Merkle sibling hashes<br /><br />- <b>Code-level analysis and exper=
imental validation of how these control blocks</b> are constructed and veri=
fied against the Taproot output, based on actual testnet spends.<br /><br /=
>- <b>Witness stack inspection and visualization of script execution</b>, s=
howing the actual runtime behavior for each script path.<br /><br />Resourc=
es:<br /><br /><b>- Part 1: 4-leaf tree construction and testnet validation=
=C2=A0<br /></b>=C2=A0 https://medium.com/@aaron.recompile/building-a-4-le=
af-taproot-tree-in-python-the-first-complete-implementation-on-bitcoin-test=
net-c8b66c331f29<br /><br /><b>- Part 2: Control block structure and stack =
visualization =C2=A0<br /></b>=C2=A0 https://medium.com/@aaron.recompile/ta=
proot-control-block-deep-analysis-stack-execution-visualization-5ff10f98032=
c<br /><br />- GitHub repo with code, testnet transactions, and diagrams =
=C2=A0<br />=C2=A0 https://github.com/btcstudy/btcstudy.github.io/tree/main=
/Not-Just-Hodling:bitcoin-script-Engineering/demo3_taproot_4leaf<br /><br /=
>This project aims to provide a fully verifiable and pedagogical example of=
non-trivial Taproot path spends, helping developers better understand scri=
pt trees, control blocks, and Tapscript execution through practical experim=
entation.<br /><br />I=E2=80=99d be happy to receive any feedback or discus=
sion around:<br />- Control block design and merkle path optimization<br />=
- Spend path visibility and privacy tradeoffs<br />- Tooling for visualizin=
g script-path execution and verification<br /><br />Thanks and best regards=
, =C2=A0<br />Aaron Zhang =C2=A0<br />[@aaron.recompile](https://medium.com=
/@aaron.recompile) =C2=A0<br />GitHub: https://github.com/btcstudy
<p></p>
-- <br />
You received this message because you are subscribed to the Google Groups &=
quot;Bitcoin Development Mailing List" group.<br />
To unsubscribe from this group and stop receiving emails from it, send an e=
mail to <a href=3D"mailto:bitcoindev+unsubscribe@googlegroups.com">bitcoind=
ev+unsubscribe@googlegroups.com</a>.<br />
To view this discussion visit <a href=3D"https://groups.google.com/d/msgid/=
bitcoindev/d4f04a90-9842-4260-8e7b-79ed2bc00adan%40googlegroups.com?utm_med=
ium=3Demail&utm_source=3Dfooter">https://groups.google.com/d/msgid/bitcoind=
ev/d4f04a90-9842-4260-8e7b-79ed2bc00adan%40googlegroups.com</a>.<br />
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