Block v2, Height in Coinbase

  BIP: 34
  Layer: Consensus (soft fork)
  Title: Block v2, Height in Coinbase
  Authors: Gavin Andresen 
  Status: Deployed
  Type: Specification
  Assigned: 2012-07-06

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.