How Does the Difficulty Adjustment Mechanism Affect the Attack Cost over Time?

The difficulty adjustment mechanism is designed to stabilize the block time. If an attacker suddenly introduces a massive amount of rented hash rate, blocks will be found much faster.

The network will then rapidly increase the difficulty, making the attack proportionally more expensive to sustain over a longer period. This mechanism effectively raises the long-term cost of a sustained 51% attack, protecting the network.