BIP 34 (block height in coinbase): Block v2, Height in Coinbase
Also known as: block height in coinbase, BIP34, BIP-0034.
In plain English: Upgraded blocks to version 2 and required each block's coinbase transaction (the one paying the miner) to include the block's height. This makes every coinbase unique, preventing duplicate transactions, and set a pattern for rolling out later upgrades.
- Status
- Deployed
- Type
- Specification
- Layer
- Consensus (soft fork)
- Authors
- Gavin Andresen
- Assigned
- Last changed
- Activated
- Block 227,931 (2013-03)
- Topics
- Consensus, Blocks, Validation
- Source
- bip-0034.mediawiki on GitHub · Markdown
Full specification
Abstract
Bitcoin blocks and transactions are versioned binary structures. Both currently use version 1. This BIP introduces an upgrade path for versioned transactions and blocks. A unique value is added to newly produced coinbase transactions, and blocks are updated to version 2.
Motivation
- Clarify and exercise the mechanism whereby the bitcoin network collectively consents to upgrade transaction or block binary structures, rules and behaviors.
- Enforce block and transaction uniqueness, and assist unconnected block validation.
Specification
- Treat transactions with a version greater than 1 as non-standard (official Satoshi client will not mine or relay them).
- Add height as the first item in the coinbase transaction's scriptSig, and increase block version to 2. The format of the height is "minimally encoded serialized CScript" -- first byte is number of bytes in the number (will be 0x03 on main net for the next 150 or so years with 223-1 blocks), following bytes are little-endian representation of the number (including a sign bit). Height is the height of the mined block in the block chain, where the genesis block is height zero (0).
- 75% rule: If 750 of the last 1,000 blocks are version 2 or greater, reject invalid version 2 blocks. (testnet3: 51 of last 100)
- 95% rule ("Point of no return"): If 950 of the last 1,000 blocks are version 2 or greater, reject all version 1 blocks. (testnet3: 75 of last 100)
Backward compatibility
All older clients are compatible with this change. Users and merchants should not be impacted. Miners are strongly recommended to upgrade to version 2 blocks. Once 95% of the miners have upgraded to version 2, the remainder will be orphaned if they fail to upgrade.
Implementation
https://github.com/bitcoin/bitcoin/pull/1526
Result
Block number 227,835 (timestamp 2013-03-24 15:49:13 GMT) was the last version 1 block.