Rainbow tables are a clever way to implement a time/space trade-off for finding the inverse of a hash value in general by doing a lot of precalculation (see wik

Rainbow tables are a clever way to implement a time/space trade-off for finding the inverse of a hash value in general by doing a lot of precalculation (see wikipedia, the core nice idea there is explained under "hash chains" in the Rainbow Table page). Besides, rainbow tables are supposed to be pointless because everyone's supposed to be using salt with their passwords...