Difficulty Bomb: Ethereum's Increasing Difficulty in Mining

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7 Apr 2024

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Updated December 14, 2023
Reviewed by AMILCAR CHAVARRIA
Fact checked by KIRSTEN ROHRS SCHMITT

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What Was the Difficulty Bomb?

Ethereum launched using the proof-of-work consensus mechanism, an algorithm that uses large amounts of energy and computational power. This mechanism uses a competitive reward system that encourages mining—and centralized mining farms that have taken over the network. However, this centralization goes against the original decentralization tenet behind cryptocurrency.
Ethereum's "difficulty bomb" referred to the intentional and sudden increase in mining difficulty on the blockchain. It was released to coincide with the blockchain's transition to proof-of-stake. The intent behind the difficulty bomb was to exponentially increase the amount of time it took to mine a new block on the Ethereum blockchain so that it:

Encouraged cryptocurrency miners to move away from energy-intensive proof-of-work mining by removing the incentive
Took away the ability to centralize currency creation and ownership
Discouraged blockchain forks
Forced node upgrades

KEY TAKEAWAYS

Ethereum’s “difficulty bomb” referred to a sudden increase in mining difficulty to discourage miners from opting to stay with the proof-of-work mechanism after it transitioned to proof-of-stake.
Difficulty refers to the time and computational power needed to verify a cryptocurrency's transactions within a blockchain under the proof-of-work mechanism.
Ethereum's difficulty bomb deployed at block 15530314 on Sept. 14, 2022, the day before "The Merge" went live.1
2

Understanding the Difficulty Bomb

In the world of cryptocurrency, the term difficulty describes a setting that keeps the network randomly guessing for the target solution for a prescribed amount of time. It is calculated in different ways by different blockchains, but the Bitcoin blockchain uses the current difficulty, the expected time, and the actual time to calculate the new difficulty.
Mining a cryptocurrency is often confused with creating a coin; however, mining is the verification process that involves guessing a 64-character hash that is less than the target value set by the network. When a miner's machine guesses correctly, they are rewarded with a coin.

Ethereum's developers created the difficulty bomb to increase the difficulty of solving the hash exponentially, eventually making it too expensive in time and energy to be worth the cost.
Ethereum's developers always intended to move to proof-of-stake, which is claimed to consume 99.95% less energy than proof-of-work.3
Ethereum’s difficulty bomb is a deterrent for miners, who may have wanted to fork the original blockchain to continue mining using the PoW mechanism. The primary reason miners didn't want to switch to PoS is that the expensive mining machines and farms they created would become obsolete, at least as far as earning rewards for profits.

Difficulty Bomb Challenges

Migrating to PoS was an enormous challenge for the developers—they had to keep pushing the difficulty bomb release date back because The Merge kept being rescheduled. Releasing the bomb before upgrading to PoS would have been counterproductive—the difficulty bomb would have significantly slowed down transactions and severely congested the network.
There have been six upgrades that, among other fixes, pushed back the difficulty bomb:

2017: Byzantium update4
2019: Constantinople update5
2020: Muir Glacier update (difficulty bomb only)6
2021: London update7
2021: Arrow Glacier update (difficulty bomb only)8
2022: Gray Glacier (difficulty bomb only)9

Is Ethereum Getting Harder to Mine?

Ether (ETH), the native Ethereum blockchain and ecosystem cryptocurrency, can no longer be mined due to the transition from proof-of-work to proof-of-stake consensus.

What Does Ethereum Difficulty Mean?

Ethereum difficulty referred to the increasing amount of time it took to validate transactions under the proof-of-work (PoW) consensus mechanism. The transition to proof-of-stake in September 2022 removed PoW as the consensus mechanism for the Ethereum blockchain, so difficulty is no longer an issue.

What Will Happen to Ethereum Miners After The Merge?

Ether (ETH), Ethereum's native cryptocurrency, can no longer be mined. Miners will need to switch to a minable cryptocurrency if they want to continue mining. Alternatively, they can switch their mining activities to validation activities to earn rewards and help secure the blockchain.

The Bottom Line

Ethereum's difficulty bomb was an attempt by its developers to discourage miners from forking the blockchain and continuing proof-of-work on an Ethereum-like blockchain. It was supposed to work by increasing the difficulty level to a point where mining was impossible when the blockchain switched to proof-of-stake. However, Ethereum Classic forked long before the transition, and other mineable forks were created.
The comments, opinions, and analyses expressed on Investopedia are for informational purposes only. Read our warranty and liability disclaimer for more info. As of the date this article was written, the author does not own cryptocurrency.
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