Sealminer A4 Ultra Hydro
Bitcoin & Bitcoin Cash ASIC Miner
886TH
HASHRATE
9.45W/TH
EFFICIENCY
8373W
POWER
£820.82
EST. MONTHLY
NO PAYBACK
EST. ROI
This guide explains BIP 433 Pay to Anchor (P2A) in plain English. It covers the problem behind the BIP, why it matters and whether the proposal is part of Bitcoin today.
TL;DR
- What it is: BIP 433 is a Draft informational description of Pay to Anchor, a compact keyless output intended to support child-pays-for-parent fee bumping of presigned transactions. The output uses a fixed witness-v1 program and spends with no signature or witness data.
- Why it matters: P2A is a deliberately keyless fee-bump hook, not a protected output. It is useful when combined with correct package economics, topology controls and monitoring that assumes any network participant may construct the child spend.
- Current position: BIP 433 is a Draft informational description of Pay to Anchor, a compact keyless output intended to support child-pays-for-parent fee bumping of presigned transactions.
BIP 433 Pay to Anchor (P2A) in simple English
BIP 433 Pay to Anchor (P2A): The pattern gives a presigned parent transaction a small hook for later CPFP when the required feerate is known.
Simple example
A node operator is checking BIP 433 Pay to Anchor (P2A). Watchtowers can bump without receiving special anchor keys. BIP 433 is Draft and Informational at the applications layer.
Key terms in plain English
- BIP:
- Bitcoin Improvement Proposal: a document describing a proposed rule, standard or process. Its status must be checked separately.
- Consensus:
- The shared rules full nodes use to decide whether blocks and transactions are valid.
- Node:
- A computer running Bitcoin software that checks data and communicates with other peers.
Status and scope
BIP 433 is Draft and Informational at the applications layer. It documents a standard output and spending policy rather than changing consensus validity.
Script form
The P2A script is OP_1 followed by the two-byte 0x4e73 witness program. Its published mainnet, testnet and regtest addresses are fixed representations, not user-derived custody addresses.
Keyless spend
A standard P2A input carries no witness. There is no privileged key, so any party can attach a child that contributes fees to the package.
Fee-bump purpose
The pattern gives a presigned parent transaction a small hook for later CPFP when the required feerate is known. Watchtowers can bump without receiving special anchor keys.
Griefing risk
Public spendability also lets an adversary attach an undesirable child. The BIP recommends considering TRUC topology limits and other anti-pinning measures rather than treating P2A alone as protection.
Related policies
P2A and ephemeral dust are distinct. Its default dust threshold is 240 satoshis; ephemeral-dust rules may allow a single dust output in a zero-fee parent that is spent within a package.
How specialists test it
Developers test the proposal with made-up data on an isolated test network. They check normal cases and deliberately invalid cases. Different implementations should reach the same result before anyone relies on the proposal.
Frequently asked questions
What is the main point of BIP 433 Pay to Anchor (P2A)?
BIP 433 Pay to Anchor (P2A): The pattern gives a presigned parent transaction a small hook for later CPFP when the required feerate is known.
For BIP 433 Pay to Anchor (P2A), what should a beginner know about status and scope?
BIP 433 is Draft and Informational at the applications layer. It documents a standard output and spending policy rather than changing consensus validity.
For BIP 433 Pay to Anchor (P2A), what should a beginner know about script form?
The P2A script is OP_1 followed by the two-byte 0x4e73 witness program.
For BIP 433 Pay to Anchor (P2A), what should a beginner know about keyless spend?
A standard P2A input carries no witness. There is no privileged key, so any party can attach a child that contributes fees to the package.
Conclusion
P2A is a deliberately keyless fee-bump hook, not a protected output. It is useful when combined with correct package economics, topology controls and monitoring that assumes any network participant may construct the child spend.
Primary sources
Check the current specification status and the documentation for the exact implementation you operate before moving production funds or changing a mining node.
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