Difficulty growing exponentially with block chain length?

Question

The Ethereum Yellow Paper includes on page 6 in equation (44) a term which contributes to the difficulty of a block. This term is added to the difficulty in equation (39).

is an exponential function which depends on the length of the block chain only. The longer the chain up to the current block , the higher and is growing exponentially.

This looks very strange. It would mean that the longer the chain, the higher the difficulty and the more difficult and costly it becomes to mine a new block. This is counter intuitive.

Does really depend on the length of the block chain? Or is this a typo on in the paper and should it actually depend on something else, i.e. the gas limit instead of the chain length ?

Answer 1

That portion of the difficulty adjustment formula is the difficulty bomb that will make mining proof-of-work increasingly more difficult to force miners to move to a proof-of-stake network.

Further information in the following Q&As:

• What is the "difficulty bomb" and what is the goal of it?
• When will the difficulty bomb make mining impossible?
• What if difficulty bomb makes mining impossible before POS release?
• How does the Ethereum Homestead difficulty adjustment algorithm work?