The Constantinople Hard Fork: What You Need to Know

The Constantinople Upgrade: What You Need to Know

On January 16th, the Constantinople upgrade of Ethereum is expected to happen. Here’s what’s happening and what it means.

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A Brief Overview

Constantinople is the name of Ethereum’s next hard fork system upgrade. It is part of the multi-step journey towards Serenity, which implements revolutionary protocols such as Proof of Stake. On December 6th, 2018, the Ethereum core developers voted to proceed with Constantinople, which will be implemented at block 7,080,000. With an average block time of ~14.5 seconds, that puts the estimated date of the Constantinople hard fork at January 16th, 2019.

But doesn’t a hard fork mean a currency split? Not necessarily. One of the most highly publicized hard forks in Ethereum’s history was the hard fork that occurred after the DAO hack and restored the stolen ETH to the original owners. Because that hard fork was unplanned and contentious, the community split between those who supported the restoration of funds (Ethereum) and those who rejected it on grounds of immutability (Ethereum Classic). Uncontentious hard forks, however, have happened in Ethereum’s history to implement upgrades without ‘currency’ splits, including Homestead and Byzantium. Because the Ethereum community at large expects and supports the Constantinople hard fork, the token consequences as seen in the ETH/ETC hard fork are not expected.

Constantinople will integrate 5 Ethereum Improvement Proposals (EIPs), which tackle a number of cost, speed, functionality, and miner issues.

EIP 145: Bitwise Shifting Instructions [Efficiency & Speed]

EIP 145 will add Bitwise shifting instructions to the Ethereum Virtual Machine (EVM). The instructions allow for bits of binary information to move to the left and to the right. This improvement means the execution of shifts in smart contracts will be 10x cheaper.

EIP 1052: Smart Contract Verification [Speed & Energy]

EIP 1052 allows for smart contracts to verify one another by pulling just the hash of the other smart contract. Before Constantinople, smart contracts would have to pull the entire code of another in order to verify, which took time and energy to perform.

EIP 1014: CREATE2 [Scalability]

EIP 1014, known by CREATE2, was developed by Vitalik Buterin. The upgrade improves the enablement of state channels, an Ethereum scaling solution based on off-chain transactions.

EIP 1283: SSTORE [cost]

This proposal — the full name of which is ‘Net Gas Metering for SSTORE Without Dirty Maps’ — reduces the gas cost for the SSTORE operation. This reduction enables multiple updates to occur within a transaction more cheaply.

EIP 1234: Block Rewards & Difficulty Bomb Delay

EIP 1234 is one of the most highly-discussed Constantinople upgrade. It is comprised of two components: Block Reward Reduction and Difficulty Bomb Delay.

Block Reward Reduction
Currently, when a miner succeeds at mining a block on the Ethereum network, they receive 3 ETH as a reward. After the Constantinople hard fork, miners will receive 2 ETH per block as a reward. This reduction from 3 ETH to 2 ETH is known as the “Thirdening.” This is the second time in Ethereum’s history when block rewards have been reduced. The Byzantium hard fork in late 2017 reduced the rewards from 5 ETH to 3 ETH.

The reduction in ETH rewards over the years is in the effort to reduce the inflation of Ether in basic supply and demand economics. Ethereum is also not the only network to implement this strategy. Bitcoin halves its block rewards every 210,000 block towards its eventual cap of 21 million Bitcoin. Though the total supply of Ether does not have an established limit, reducing the inflation rate is an essential tool to ensure scarcity.

For a more in-depth look at the Thirdening and its consequences, read here.

Difficulty Bomb Delay
The Difficulty Bomb is a mechanism that, if activated, would increase the energy required (i.e. the ‘difficulty) to mine a new block until it becomes impossible and no new blocks can be mined. At this point, the Ethereum network would become ‘frozen.’ EIP 1234 delays the implementation of the Difficulty Bomb for another twelve months, at which point it will be voted upon again.

The Difficulty Bomb was originally included in the network in September 2015. Its purpose is to support the eventual transition away from Proof of Work towards Proof of Stake. When PoS is implemented, miners could theoretically choose to support the old PoW chain, thus causing a split in the community and the creation of two separate chains — one maintained by stakers and one maintained by miners. The solution for this not to happen is to implement the Difficulty Bomb, which would eventually phase out the efficacy of mining and allow for the complete transition of the network over to PoS without the threat of a contentious hard fork.


The Constantinople hard fork will be an exciting evolution for the Ethereum community. With the implementation of efficiency, speed, and lower costs, we are moving closer towards the full realization of Ethereum’s potential.

Everett Muzzy, ConsenSys