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What is the Ethereum Difficulty Bomb (Ice Age)?


Ethereum's "Difficulty Bomb" refers to a mechanism that, at a predefined block number, increases the difficulty level of puzzles in the Proof of Work mining algorithm resulting in longer than normal block times (and thus less ETH rewards for miners). This mechanism increases the difficulty exponentially over time and eventually leads to what is referred to as the "Ice Age" - that is, the chain becomes so difficult to mine that it grinds to a halt and stops producing blocks (freezes).

Why the Difficulty Bomb Exists

The Difficulty Bomb was originally put in place for a variety of reasons:

  • To act as a deterrant for miners who wish to continue mining the Ethereum 1.0 (Proof of Work) chain once the network moved fully to the Ethereum 2.0 (Proof of Stake) chain
  • To ensure that the core developers of Ethereum 1.0 are "forced" to upgrade the network via a hard fork (if only to delay the effects of the bomb) so that the network does not stagnate innovation-wise

Technical Details of the Difficulty Bomb

Work in progress.

Effects of the Difficulty Bomb

The effect of the Difficulty Bomb is easily seen in the 'Ethereum Block Time History' chart from Etherscan (you'll notice that it is a step-function that increases block times the longer that it exists on the chain).

ethereum block times

Is the Difficulty Bomb Still Necessary?

There is an open debate as to whether the Difficulty Bomb is still required because Ethereum 2.0 is now being deployed as a seperate blockchain (instead of a direct upgrade to the Ethereum 1.0 chain) and the bomb has been delayed without any fanfare in both the Byzantine and Constantinople network upgrades.