nVersion bits for general purpose use

The five-minute read

One action, walked through

1. Open BIP 320 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 reserves 16 bits of the block header nVersion field for general purpose use and removes their meaning for the purpose of version bits soft-fork signalling.
3. Name the object that changes: MUST, NOT, REQUIRED.
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 320 at the status the text itself states: Draft.
• The object that has to change is MUST, NOT, REQUIRED. A neighbouring document with a similar name is not this one.
• Wallet support is not the same as consensus validity.

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

• What is covered by the signed bytes in nVersion bits for general purpose use?
• Can the same signature be replayed on another chain, account, or message?
• Which primitive does the text require: MUST, NOT, REQUIRED?

Terms

BIP 320

The public text titled nVersion bits for general purpose use.

Draft

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

The problem the paper names

A signature that does not commit to what the user saw can be replayed into a different spend, a different chain, or a different message.

What the design proposes

• This BIP reserves 16 bits of the block header nVersion field for general purpose use and removes their meaning for the purpose of version bits soft-fork signalling.
• The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.
• There are a variety of things that miners may desire to use some of the nVersion field bits for.

How the mechanism is specified

• Taken from the specification, the next constraint is: The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.
• Locate MUST, NOT, REQUIRED in BIP 320 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 signature scheme is not a privacy system. It hides the signer only if the protocol says so.
• Wallet support is not the same as consensus validity.
• 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 320 when a pitch says 'nVersion bits for general purpose use' without saying whether the rule is consensus, policy, or an interface. The number is the citation. The pitch is not.