Transaction Signature Verification for Version 0 Witness Program

The five-minute read

One action, walked through

1. Open BIP 143 and read the status line before the examples.
2. Write down the rule in one sentence. A fair version of that sentence is: This proposal defines a new transaction digest algorithm for signature verification in version 0 witness program, in order to minimize redundant data hashing in verification, and to cover the input value by the signature.
3. Name the object that changes: ECDSA, CHECKSIG, CHECKSIGVERIFY.
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 143 at the status the text itself states: Deployed.
• The object that has to change is ECDSA, CHECKSIG, CHECKSIGVERIFY. 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 Transaction Signature Verification for Version 0 Witness Program, 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: ECDSA, CHECKSIG, CHECKSIGVERIFY?

Terms

BIP 143

The public text titled Transaction Signature Verification for Version 0 Witness Program.

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

• This proposal defines a new transaction digest algorithm for signature verification in version 0 witness program, in order to minimize redundant data hashing in verification, and to cover the input value by the signature.
• There are 4 ECDSA signature verification codes in the original Bitcoin script system: CHECKSIG , CHECKSIGVERIFY , CHECKMULTISIG , CHECKMULTISIGVERIFY (“sigops”).
• According to the sighash type ( ALL , NONE , SINGLE , ANYONECANPAY ), a transaction digest is generated with a double SHA256 of a serialized subset of the transaction, and the signature is verified against this digest with a given public key.

How the mechanism is specified

• Taken from the specification, the next constraint is: There are 4 ECDSA signature verification codes in the original Bitcoin script system: CHECKSIG , CHECKSIGVERIFY , CHECKMULTISIG , CHECKMULTISIGVERIFY (“sigops”).
• Locate ECDSA, CHECKSIG, CHECKSIGVERIFY in BIP 143 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 143 when a pitch says 'Transaction Signature Verification for Version 0 Witness Program' without saying whether the rule is consensus, policy, or an interface. The number is the citation. The pitch is not.