cuckoo

> proving the memory hardness seems more harduous In fact, several submissions to the Zcash Open Miner Contest, at https://zcashminers.org/submissions exhibit time-memory tradeoffs that were not considered in that paper, invalidating some of its claims. My own, memory latency bound, proof-of-work called Cuckoo Cycle https://github.com/tromp/cuckoo offers $5000 in bounties for invalidating its claims of near-optimal implementations and trade-off resistence.

It doesn't make much sense to use a memory hard hash function as part of the Hashcash proof of work system, since 1) Proof of Work systems should make verification as cheap as possible. 2) Hashcash makes verification as expensive as proof attempt. Project pages for the above asymmetric Proof of Work systems, which do not suffer from this conflict, can be found at https://github.com/khovratovich/equihash https://github.com/tromp/cuckoo