Steven Barclay 95637e0fa0 Add Equihash implementation for use in ASIC-resistant PoW ... Implement the Equihash (https://eprint.iacr.org/2015/946.pdf) algorithm for solving/verifying memory-hard client-puzzles/proof-of-work problems for ASIC-resistant DoS attack protection. The scheme is asymmetric, so that even though solving a puzzle is slow and memory-intensive, needing 100's of kB to MB's of memory, the solution verification is instant. Instead of a single 64-bit counter/nonce, as in the case of Hashcash, Equihash solutions are larger objects ranging from 10's of bytes to a few kB, depending on the puzzle parameters used. These need to be stored in entirety, in the proof-of-work field of each offer payload. Include logic for fine-grained difficulty control in Equihash with a double-precision floating point number. This is based on lexicographic comparison with a target hash, like in Bitcoin, instead of just counting the number of leading zeros of a hash. The code is unused at present. Also add some simple unit tests.		2021-12-07 09:35:42 +01:00
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src	Add Equihash implementation for use in ASIC-resistant PoW	2021-12-07 09:35:42 +01:00