IIRC, a quantum computer reduces preimage attacks (first or second) to the difficulty of collision attacks, but doesn't improve collision beyond the best classi

IIRC, a quantum computer reduces preimage attacks (first or second) to the difficulty of collision attacks, but doesn't improve collision beyond the best classical attacks, which can be run on faster and cheaper hardware. It also may or may not benefit from any cryptanalysis applicable to collision attacks. So if you're secure against (classical) collision attacks, you don't need to worry about quantum attacks (collision or preimage).