Validation of Taproot Scripts

The five-minute read

One action, walked through

1. Open BIP 342 and read the status line before the examples.
2. Write down the rule in one sentence. A fair version of that sentence is: The rules below only apply when validating a transaction input for which all of the conditions below are true: The transaction input is a '''segregated witness spend''' (i.e., the scriptPubKey contains a witness program as defined in [[bip-0141.mediawiki|BIP141]]).
3. Name the object that changes: BIP141, BIP341, P2SH.
4. Ask what an old client, an old contract, or an offline counterparty does. If the document is silent, the silence is part of the design.

The argument, unpacked

What has to be true

• You are implementing BIP 342 at the status the text itself states: Deployed.
• The object that has to change is BIP141, BIP341, P2SH. A neighbouring document with a similar name is not this one.
• Activation is a separate mechanism from the opcode or the sighash. This page does not pick a height.

What happened after the paper

The source marks this deployed. That is a statement about the text, not a promise that every wallet or node has shipped it. Later documents can narrow, replace, or ignore this one. Cite the number you mean.

What to check before you use the idea

• Which bytes become invalid under Validation of Taproot Scripts, and which old transactions stay valid?
• Is enforcement in consensus, or only in the mempool policy of one client?
• Which of these objects does the text actually define: BIP141, BIP341, P2SH?

Terms

BIP 342

The public text titled Validation of Taproot Scripts.

Deployed

The document's own label for how finished the text is. It is not a market fact.

The problem the paper names

Bitcoin script and block validity only change when a soft fork says an old pattern is now invalid. Without that rule, every node is free to accept what this document wants to reject.

What the design proposes

• The rules below only apply when validating a transaction input for which all of the conditions below are true: The transaction input is a '''segregated witness spend''' (i.e., the scriptPubKey contains a witness program as defined in [[bip-0141.mediawiki|BIP141]]).
• It is a '''taproot spend''' as defined in [[bip-0341.mediawiki#design|BIP341]] (i.e., the witness version is 1, the witness program is 32 bytes, and it is not P2SH wrapped).
• It is a '''script path spend''' as defined in [[bip-0341.mediawiki#design|BIP341]] (i.e., after removing the optional annex from the witness stack, two or more stack elements remain).

How the mechanism is specified

• Taken from the specification, the next constraint is: It is a '''taproot spend''' as defined in [[bip-0341.mediawiki#design|BIP341]] (i.e., the witness version is 1, the witness program is 32 bytes, and it is not P2SH wrapped).
• Locate BIP141, BIP341, P2SH in BIP 342 and apply it to one transaction or call.
• Then check the failure the class of rule always has: a node that did not upgrade, a reverted call, a replayed signature, or a peer that does not speak the message.

What this page does not treat as proven

• A soft fork does not bind a node that never upgrades. It binds the nodes that enforce the new rejection.
• Activation is a separate mechanism from the opcode or the sighash. This page does not pick a height.
• The source marks this deployed. That is a statement about the text, not a promise that every wallet or node has shipped it.

Why a venture studio still reads it

Use BIP 342 when a pitch says 'Validation of Taproot Scripts' without saying whether the rule is consensus, policy, or an interface. The number is the citation. The pitch is not.