EIP4345 - Difficulty Bomb Delay to May 2022

# Abstract

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 10,500,000 blocks later than the actual block number.

# Motivation

Targeting for the Shanghai upgrade and/or the Merge to occur before May 2022. Either the bomb can be readjusted at that time, or removed all together.

# Specification

# 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 - 10_500_000) if block.number >= FORK_BLOCK_NUMBER else block.number

# Rationale

The following script predicts a 0.25 second delay to block time by May 2022 and a 1 second delay by June. 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 for predictions:
    current_blknum = 13346561
    current_difficulty = 9191929451665642
    block adjustment = 10500000
    months = 7 # May 2022
    months = 8 # June 2022
    '''
    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(13346561,9191929451665642,10500000,6.5)

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# 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.