Paying people to hash
I want to build software that allows people to get paid to use hashcat. Basically, the software is like a bitcoin miner, or a standard GPU miner, but instead of mining it's hashing using hashcat. Users get paid based on the hashing power they produce, and are paid into a wallet. I want to then distribute the software to thousands of people, who would all be running the software and would be getting paid to run it.

Advertisers could then upload a hash file that they want cracked, and it gets distributed to all the users of the software to perform hashes to. The problem is, how would I distribute the hashing power to everyone so that everyone performs a different part of the hashing queue so no one does the same hash twice? 

So basically user A runs the first 1%, user B runs the 2nd 1% (but not really in that order). Basically when they turn the software on, it needs to figure out where it has left off, and needs to allocate work for that user.

Does something like this already exist? If not, how would I go about it?