I'm not particularly familiar with this stuff, but aren't the cost factors for hash algorithms essentially the number of times to nest the hash function? i.e. `

I'm not particularly familiar with this stuff, but aren't the cost factors for hash algorithms essentially the number of times to nest the hash function? i.e. `hash(hash(hash(hash(hash(input)))))` type of thing. So it would cost more, but only for the first round? After that the size is reduced to the size of the image of the hash for future rounds? That said, a few MB is a lot for one client to post if you have a significant amount of traffic. Just hash client side first.