kiosk-pow-equihash

https://github.com/kiosk-hq/kiosk

kiosk-pow-equihash is the shipped default proof-of-work backend for the Kiosk framework: a pure-Ruby Equihash (Biryukov & Khovratovich birthday- collision PoW) VERIFIER built on kiosk-pow, which holds the pure-Ruby BLAKE2b-256. The gem depends on neither kiosk-core nor Rails. `Kiosk::Pow::Equihash.verify(salt:, params:, nonce:)` recomputes the 2^k BLAKE2b-256 hashes named by the proof's indices, checks that they XOR to zero over all n bits, and walks the Wagner collision tree (per-level XOR cancellation plus the Zcash-canonical subtree ordering that pins one canonical form per solution). Difficulty is set by (n, k) alone — there is no post-hoc target check. Default parameters are n=168, k=7, chosen by the benchmark in bench/: the largest params whose reference solve stays inside a consumer-laptop budget (p95 ~10 s on one M-series laptop core, the only hardware the seconds have ever been measured on; the ~1.3 GiB peak is THIS solver's table, not the host's -- and not a floor (n, k) imposes on every implementation, since a memory-optimised solver trades it for time) while verify costs 128 BLAKE2b evaluations — ~22 ms and a few KB in pure Ruby without YJIT. That asymmetry is the point: the gem prices a request, it does not equalise hardware. Equihash is neither ASIC- nor GPU-proof (it was ASIC'd on Zcash); abuse resistance comes from the reputation policy's N-proofs knob and caps, not from this algorithm. Ships the provider-side verifier only. A reference Python + numpy solver (solve.py) rides along for parity testing and for assistants that need one; production solving is the client's concern.