What is Equihash?
Crypto Glossary Definition
An asymmetric memory-bound Proof of Work system that is based on the generalized birthday problem. Its memory intensive nature can be used to prevent ASIC mining. ZCash and its numerous forks are the most notable cryptocurrencies that use the Equihash algorithm. Developed by Alex Biryukov and Dmitry Khovratovich at the University of Luxembourg.
Why Equihash Matters
Equihash's deliberate memory-hardness was a direct response to Bitcoin's mining history: by making the algorithm expensive in RAM rather than raw compute, it aimed to keep specialized ASIC hardware from dominating mining the way it did on Bitcoin's SHA-256. In practice, ASICs for Equihash were eventually built anyway, which is a recurring pattern across "ASIC-resistant" algorithms.
Equihash in Practice
A hobbyist miner researching how to participate in mining Zcash quickly discovers that the usual approach, buying a specialized ASIC rig built for Bitcoin's SHA-256 algorithm, won't work here. Zcash uses Equihash, a proof-of-work algorithm deliberately designed to require large amounts of RAM rather than raw processing speed, based on a cryptographic puzzle known as the generalized birthday problem. The miner instead configures a rig built around consumer graphics cards with high memory bandwidth, since GPUs handle Equihash's memory demands more efficiently than CPUs and, in theory, more fairly than specialized chips. For a while this works as intended, and mining stays relatively accessible to hobbyists running GPU rigs at home rather than requiring warehouse-scale ASIC farms. Eventually, though, manufacturers develop Equihash-specific ASICs anyway, and the miner notices hash rates and difficulty climbing sharply as those devices come online, squeezing out GPU miners much as ASICs once did on Bitcoin. This trajectory, an algorithm designed for ASIC resistance eventually getting ASICs built for it regardless, is a pattern that has repeated across several so-called memory-hard mining algorithms, and it's a useful case study in why 'ASIC-resistant' is often a temporary property rather than a permanent guarantee.
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