Pay-to-Merkle-Root (P2MR)

The five-minute read

One action, walked through

1. Open BIP 360 and read the status line before the examples.
2. Write down the rule in one sentence. A fair version of that sentence is: We define the Pay-to-Merkle-Root (P2MR) output structure as follows: A P2MR output is similar to a P2TR output (as defined in [[bip-0341.mediawiki|BIP 341]]); however, unlike P2TR outputs, we disable the key path spend for the benefit of quantum resistance by omitting the internal key and the tap tweak step.
3. Name the object that changes: P2MR, P2TR.
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 360 at the status the text itself states: Draft.
• The object that has to change is P2MR, P2TR. 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 draft. It is not a live consensus rule just because it has a number. 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 Pay-to-Merkle-Root (P2MR), 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: P2MR, P2TR?

Terms

BIP 360

The public text titled Pay-to-Merkle-Root (P2MR).

Draft

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

• We define the Pay-to-Merkle-Root (P2MR) output structure as follows: A P2MR output is similar to a P2TR output (as defined in [[bip-0341.mediawiki|BIP 341]]); however, unlike P2TR outputs, we disable the key path spend for the benefit of quantum resistance by omitting the internal key and the tap tweak step.
• A P2MR output is then a SegWit version 2 byte followed by the Merkle root of the script tree as the witness program.
• The normative names to look up in BIP 360 are P2MR, P2TR.

How the mechanism is specified

• Taken from the specification, the next constraint is: A P2MR output is then a SegWit version 2 byte followed by the Merkle root of the script tree as the witness program.
• Locate P2MR, P2TR in BIP 360 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 draft. It is not a live consensus rule just because it has a number.

Why a venture studio still reads it

Use BIP 360 when a pitch says 'Pay-to-Merkle-Root (P2MR)' without saying whether the rule is consensus, policy, or an interface. The number is the citation. The pitch is not.