hashScriptCheck

The five-minute read

One action, walked through

1. Open BIP 18 and read the status line before the examples.
2. Write down the rule in one sentence. A fair version of that sentence is: This BIP modifies the basic format of transaction inputs and outputs, replacing the current scriptSig and scriptPubKey (scripts executed to validate a transaction) with new contents: dataSig, scriptCheck, and hashScriptCheck.
3. Name the object that changes: MUST, SHOULD, MAY.
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 18 at the status the text itself states: Complete.
• The object that has to change is MUST, SHOULD, MAY. 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 complete. 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 hashScriptCheck, 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: MUST, SHOULD, MAY?

Terms

BIP 18

The public text titled hashScriptCheck.

Complete

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

• This BIP modifies the basic format of transaction inputs and outputs, replacing the current scriptSig and scriptPubKey (scripts executed to validate a transaction) with new contents: dataSig, scriptCheck, and hashScriptCheck.
• The purpose of pay-to-script-hash is to move the responsibility for supplying the conditions to redeem a transaction from the sender of the funds to the redeemer.
• The benefit is allowing a sender to fund any arbitrary transaction, no matter how complicated, using a fixed-length 20-byte hash that is short enough to scan from a QR code or easily copied and pasted.

How the mechanism is specified

• Taken from the specification, the next constraint is: The purpose of pay-to-script-hash is to move the responsibility for supplying the conditions to redeem a transaction from the sender of the funds to the redeemer.
• Locate MUST, SHOULD, MAY in BIP 18 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 complete. 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 18 when a pitch says 'hashScriptCheck' without saying whether the rule is consensus, policy, or an interface. The number is the citation. The pitch is not.