reorg_bitcoin.py

# https://twitter.com/cz_binance/status/1125996194734399488

# block2reorg
# If you want to remove one transaction six block ago, 
# there is one solution: 
#   buy more than half of Bitcoin hash power, calculate all transaction again, until you become the longest chain and all full node accept it
# Diff is the block you want to re-org
# k is your hash power/other hash power
# x is the block you need to generate
# diff = kx - x
# diff = (k-1)x
# x = diff/(k-1)
# k = reorg_hash_percent/(1-reorg_hash_percent)
# how to use:
# reorg_hash_percent is 0.6 if you have 60% hash power, you need to generate 12 block to be longest chain.
# how_many_block(6, 0.51)
# 146
# how_many_block(6, 0.55)
# 26
# how_many_block(6, 0.6)
# 12
# how_many_block(6, 0.7)
# 4
# how_many_block(6, 0.8)
# 1

def how_many_block(block2reorg, reorg_hash_percent):
    k = reorg_hash_percent/(1 - reorg_hash_percent)
    x = block2reorg/(k - 1)
    return int(x)