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Standards Track: Core

EIP-3554: Difficulty Bomb Delay to December 2021

Authors James Hancock (@madeoftin)
Created 2021-05-06

Simple Summary

Delays the difficulty bomb to show effect the first week of December 2021.


Starting with FORK_BLOCK_NUMBER the client will calculate the difficulty based on a fake block number suggesting to the client that the difficulty bomb is adjusting 9,700,000 blocks later than the actual block number.


Targeting for the Shanghai upgrade and/or the Merge to occur before December 2021. Either the bomb can be readjusted at that time, or removed all together.


Relax Difficulty with Fake Block Number

For the purposes of calc_difficulty, simply replace the use of block.number, as used in the exponential ice age component, with the formula:

    fake_block_number = max(0, block.number - 9_700_000) if block.number >= FORK_BLOCK_NUMBER else block.number


The following script predicts a .1 second delay to blocktime the first week of december and a 1 second delay by the end of the month. This gives reason to address because the effect will be seen, but not so much urgency we don’t have space to work around if needed.

def predict_diff_bomb_effect(current_blknum, current_difficulty, block_adjustment, months):
    Predicts the effect on block time (as a ratio) in a specified amount of months in the future.
    Vars used in last prediction:
    current_blknum = 12382958
    current_difficulty = 7393633000000000
    block adjustment = 9700000
    months = 6
    blocks_per_month = (86400 * 30) // 13.3
    future_blknum = current_blknum + blocks_per_month * months
    diff_adjustment = 2 ** ((future_blknum - block_adjustment) // 100000 - 2)
    diff_adjust_coeff = diff_adjustment / current_difficulty * 2048
    return diff_adjust_coeff 

diff_adjust_coeff = predict_diff_bomb_effect(12382958,7393633000000000,9700000,6)

Backwards Compatibility

No known backward compatibility issues.

Security Considerations

Misjudging the effects of the difficulty can mean longer blocktimes than anticipated until a hardfork is released. Wild shifts in difficulty can affect this number severely. Also, gradual changes in blocktimes due to longer-term adjustments in difficulty can affect the timing of difficulty bomb epochs. This affects the usability of the network but unlikely to have security ramifications.

Copyright and related rights waived via CC0.


Please cite this document as:

James Hancock (@madeoftin), "EIP-3554: Difficulty Bomb Delay to December 2021," Ethereum Improvement Proposals, no. 3554, May 2021. [Online serial]. Available: