Difficulty Bomb: Ethereum's Increased Difficulty in Mining

What Was the Difficulty Bomb?

Ethereum's "difficulty bomb" referred to the intentional and sudden increase in mining difficulty on the blockchain. Ethereum was originally launched using proof-of-work, 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.

The difficulty bomb was released to coincide with the blockchain's transition to proof-of-stake in 2022. 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

Understanding the Difficulty Bomb

In the world of cryptocurrency, the term "difficulty" describes a setting that keeps the network guessing for the target solution for a prescribed amount of time. It is calculated in different ways by different blockchains, but the most popular proof-of-work blockchains use 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 new 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 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 update
• 2019: Constantinople update
• 2020: Muir Glacier update (difficulty bomb only)
• 2021: London update
• 2021: Arrow Glacier update (difficulty bomb only)
• 2022: Gray Glacier (difficulty bomb only)

Mechanics of Ethereum Difficulty Bomb

The Ethereum difficulty bomb was embedded in the Ethereum blockchain protocol. The "bomb" is achieved by exponentially raising the computational effort required to solve cryptographic puzzles that allow miners to add blocks to the blockchain. The bomb is designed to make these puzzles increasingly hard, leading to a significant slowdown in block creation over time.

This mechanism affects mining difficulty by making the process of finding a valid block hash more challenging as time progresses. More specifically, the bomb is activated by modifying the "block.difficulty" value in the Ethereum protocol, which directly influences the mining process. An example of a formula that dictates the mining difficult is below; this code would have been adjusted to make it unfeasible to mine Ether. Note this formula may have varied from the most recent code:

block_diff = parent_diff + parent_diff // 2048 * max(1 - (block_timestamp - parent_timestamp) // 10, -99) + int(2**((block.number // 100000) - 2))

Ethereum Network Difficulty Chat

Related to the notion of a difficulty bomb, there were metrics that can be tracked to determine how difficult it is to validate on the Ethereum network. These metrics were incredibly valuable to those trying to validate transactions in hopes of securing a profit. It's been mentioned a few times throughout this article but the easier it is to mine, the less resources (i.e. time and utilities) are needed to validate a transaction.

Since the conversation from a PoW validation system to PoS validation system, the difficult chart is now no longer maintained. However, it's still useful to look back on to understand how cryptographic changes to a network can impact how easy (i.e. profitable) it may be to mine under a proof of work system.

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 worked by increasing the difficulty level to a point where mining was impossible after the blockchain switched to proof-of-stake.

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