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  BIP: 123
  Title: BIP Classification
  Author: Eric Lombrozo <>
  Comments-Summary: No comments yet.
  Status: Active
  Type: Process
  Created: 2015-08-26

Table of Contents


This document describes a classification scheme for BIPs.

BIPs are classified by system layers with lower numbered layers involving more intricate interoperability requirements.

The specification defines the layers and sets forth specific criteria for deciding to which layer a particular standards BIP belongs.


Bitcoin is a system involving a number of different standards. Some standards are absolute requirements for interoperability while others can be considered optional, giving implementors a choice of whether to support them.

In order to have a BIP process which more closely reflects the interoperability requirements, it is necessary to categorize BIPs accordingly. Lower layers present considerably greater challenges in getting standards accepted and deployed.


Standards BIPs are placed in one of four layers:

  1. Consensus
  2. Peer Services
  3. API/RPC
  4. Applications
Non-standards BIPs may be placed in these layers, or none at all.

1. Consensus Layer

The consensus layer defines cryptographic commitment structures. Its purpose is ensuring that anyone can locally evaluate whether a particular state and history is valid, providing settlement guarantees, and assuring eventual convergence.

The consensus layer is not concerned with how messages are propagated on a network.

Disagreements over the consensus layer can result in network partitioning, or forks, where different nodes might end up accepting different incompatible histories. We further subdivide consensus layer changes into soft forks and hard forks.

Soft Forks

In a soft fork, some structures that were valid under the old rules are no longer valid under the new rules. Structures that were invalid under the old rules continue to be invalid under the new rules.

Hard Forks

In a hard fork, structures that were invalid under the old rules become valid under the new rules.

2. Peer Services Layer

The peer services layer specifies how nodes find each other and propagate messages.

Only a subset of all specified peer services are required for basic node interoperability. Nodes can support further optional extensions.

It is always possible to add new services without breaking compatibility with existing services, then gradually deprecate older services. In this manner, the entire network can be upgraded without serious risks of service disruption.

3. API/RPC Layer

The API/RPC layer specifies higher level calls accessible to applications. Support for these BIPs is not required for basic network interoperability but might be expected by some client applications.

There's room at this layer to allow for competing standards without breaking basic network interoperability.

4. Applications Layer

The applications layer specifies high level structures, abstractions, and conventions that allow different applications to support similar features and share data.

Classification of existing BIPs

Number Layer Title Owner Type Status
1 BIP Purpose and Guidelines Amir Taaki Process Active
2 BIP process, revised Luke Dashjr Process Draft
9 Version bits with timeout and delay Pieter Wuille, Peter Todd, Greg Maxwell, Rusty Russell Informational Final
10 Applications Multi-Sig Transaction Distribution Alan Reiner Informational Withdrawn
11 Applications M-of-N Standard Transactions Gavin Andresen Standard Final
12 Consensus (soft fork) OP_EVAL Gavin Andresen Standard Withdrawn
13 Applications Address Format for pay-to-script-hash Gavin Andresen Standard Final
14 Peer Services Protocol Version and User Agent Amir Taaki, Patrick Strateman Standard Final
15 Applications Aliases Amir Taaki Standard Deferred
16 Consensus (soft fork) Pay to Script Hash Gavin Andresen Standard Final
17 Consensus (soft fork) OP_CHECKHASHVERIFY (CHV) Luke Dashjr Standard Withdrawn
18 Consensus (soft fork) hashScriptCheck Luke Dashjr Standard Accepted
19 Applications M-of-N Standard Transactions (Low SigOp) Luke Dashjr Standard Draft
20 Applications URI Scheme Luke Dashjr Standard Replaced
21 Applications URI Scheme Nils Schneider, Matt Corallo Standard Final
22 API/RPC getblocktemplate - Fundamentals Luke Dashjr Standard Final
23 API/RPC getblocktemplate - Pooled Mining Luke Dashjr Standard Final
30 Consensus (soft fork) Duplicate transactions Pieter Wuille Standard Final
31 Peer Services Pong message Mike Hearn Standard Final
32 Applications Hierarchical Deterministic Wallets Pieter Wuille Informational Final
33 Peer Services Stratized Nodes Amir Taaki Standard Draft
34 Consensus (soft fork) Block v2, Height in Coinbase Gavin Andresen Standard Final
35 Peer Services mempool message Jeff Garzik Standard Final
36 Peer Services Custom Services Stefan Thomas Standard Draft
37 Peer Services Connection Bloom filtering Mike Hearn, Matt Corallo Standard Final
38 Applications Passphrase-protected private key Mike Caldwell, Aaron Voisine Standard Draft
39 Applications Mnemonic code for generating deterministic keys Marek Palatinus, Pavol Rusnak, Aaron Voisine, Sean Bowe Standard Accepted
42 Consensus (soft fork) A finite monetary supply for Bitcoin Pieter Wuille Standard Draft
43 Applications Purpose Field for Deterministic Wallets Marek Palatinus, Pavol Rusnak Informational Draft
44 Applications Multi-Account Hierarchy for Deterministic Wallets Marek Palatinus, Pavol Rusnak Standard Accepted
45 Applications Structure for Deterministic P2SH Multisignature Wallets Manuel Araoz, Ryan X. Charles, Matias Alejo Garcia Standard Accepted
47 Applications Reusable Payment Codes for Hierarchical Deterministic Wallets Justus Ranvier Informational Draft
49 Applications Derivation scheme for P2WPKH-nested-in-P2SH based accounts Daniel Weigl Informational Draft
50 March 2013 Chain Fork Post-Mortem Gavin Andresen Informational Final
60 Peer Services Fixed Length "version" Message (Relay-Transactions Field) Amir Taaki Standard Draft
61 Peer Services Reject P2P message Gavin Andresen Standard Final
62 Consensus (soft fork) Dealing with malleability Pieter Wuille Standard Withdrawn
64 Peer Services getutxo message Mike Hearn Standard Draft
65 Consensus (soft fork) OP_CHECKLOCKTIMEVERIFY Peter Todd Standard Final
66 Consensus (soft fork) Strict DER signatures Pieter Wuille Standard Final
67 Applications Deterministic Pay-to-script-hash multi-signature addresses through public key sorting Thomas Kerin, Jean-Pierre Rupp, Ruben de Vries Standard Accepted
68 Consensus (soft fork) Relative lock-time using consensus-enforced sequence numbers Mark Friedenbach, BtcDrak, Nicolas Dorier, kinoshitajona Standard Final
69 Applications Lexicographical Indexing of Transaction Inputs and Outputs Kristov Atlas Informational Accepted
70 Applications Payment Protocol Gavin Andresen, Mike Hearn Standard Final
71 Applications Payment Protocol MIME types Gavin Andresen Standard Final
72 Applications bitcoin: uri extensions for Payment Protocol Gavin Andresen Standard Final
73 Applications Use "Accept" header for response type negotiation with Payment Request URLs Stephen Pair Standard Final
74 Applications Allow zero value OP_RETURN in Payment Protocol Toby Padilla Standard Draft
75 Applications Out of Band Address Exchange using Payment Protocol Encryption Justin Newton, Matt David, Aaron Voisine, James MacWhyte Standard Draft
80 Hierarchy for Non-Colored Voting Pool Deterministic Multisig Wallets Justus Ranvier, Jimmy Song Informational Deferred
81 Hierarchy for Colored Voting Pool Deterministic Multisig Wallets Justus Ranvier, Jimmy Song Informational Deferred
83 Applications Dynamic Hierarchical Deterministic Key Trees Eric Lombrozo Standard Draft
99 Motivation and deployment of consensus rule changes ([soft/hard]forks) Jorge Timón Informational Draft
101 Consensus (hard fork) Increase maximum block size Gavin Andresen Standard Withdrawn
102 Consensus (hard fork) Block size increase to 2MB Jeff Garzik Standard Draft
103 Consensus (hard fork) Block size following technological growth Pieter Wuille Standard Draft
105 Consensus (hard fork) Consensus based block size retargeting algorithm BtcDrak Standard Draft
106 Consensus (hard fork) Dynamically Controlled Bitcoin Block Size Max Cap Upal Chakraborty Standard Draft
107 Consensus (hard fork) Dynamic limit on the block size Washington Y. Sanchez Standard Draft
109 Consensus (hard fork) Two million byte size limit with sigop and sighash limits Gavin Andresen Standard Draft
111 Peer Services NODE_BLOOM service bit Matt Corallo, Peter Todd Standard Accepted
112 Consensus (soft fork) CHECKSEQUENCEVERIFY BtcDrak, Mark Friedenbach, Eric Lombrozo Standard Final
113 Consensus (soft fork) Median time-past as endpoint for lock-time calculations Thomas Kerin, Mark Friedenbach Standard Final
114 Consensus (soft fork) Merkelized Abstract Syntax Tree Johnson Lau Standard Draft
120 Applications Proof of Payment Kalle Rosenbaum Standard Draft
121 Applications Proof of Payment URI scheme Kalle Rosenbaum Standard Draft
122 Applications URI scheme for Blockchain references / exploration Marco Pontello Standard Draft
123 BIP Classification Eric Lombrozo Process Draft
124 Applications Hierarchical Deterministic Script Templates Eric Lombrozo, William Swanson Informational Draft
125 Applications Opt-in Full Replace-by-Fee Signaling David A. Harding, Peter Todd Standard Accepted
126 Best Practices for Heterogeneous Input Script Transactions Kristov Atlas Informational Draft
130 Peer Services sendheaders message Suhas Daftuar Standard Accepted
131 Consensus (hard fork) "Coalescing Transaction" Specification (wildcard inputs) Chris Priest Standard Draft
132 Committee-based BIP Acceptance Process Andy Chase Process Withdrawn
133 Peer Services feefilter message Alex Morcos Standard Draft
134 Consensus (hard fork) Flexible Transactions Tom Zander Standard Draft
140 Consensus (soft fork) Normalized TXID Christian Decker Standard Draft
141 Consensus (soft fork) Segregated Witness (Consensus layer) Eric Lombrozo, Johnson Lau, Pieter Wuille Standard Draft
142 Applications Address Format for Segregated Witness Johnson Lau Standard Deferred
143 Consensus (soft fork) Transaction Signature Verification for Version 0 Witness Program Johnson Lau, Pieter Wuille Standard Draft
144 Peer Services Segregated Witness (Peer Services) Eric Lombrozo, Pieter Wuille Standard Draft
145 API/RPC getblocktemplate Updates for Segregated Witness Luke Dashjr Standard Draft
146 Consensus (soft fork) Dealing with signature encoding malleability Johnson Lau, Pieter Wuille Standard Draft
147 Consensus (soft fork) Dealing with dummy stack element malleability Johnson Lau Standard Draft
150 Peer Services Peer Authentication Jonas Schnelli Standard Draft
151 Peer Services Peer-to-Peer Communication Encryption Jonas Schnelli Standard Draft
152 Peer Services Compact Block Relay Matt Corallo Standard Draft