Equihash is a proof-of-work hashing algorithm developed by Alex Biryukov and Dmitry Khovratovich and introduced by the University of Luxembourg’s research group called CryptoLUX, which they were a part of, at the Network and Distributed System Security Symposium 2016 in San Diego.
Biryukov and Khovratovich designed Equihash to fight with a problem of the ASICs domination in the Bitcoin-like systems. In Equihash’s whitepaper they wrote: “Proof-of-work is a central concept in modern cryptocurrencies and denial-of-service protection tools, but the requirement for fast verification so far made it an easy prey for GPU-, ASIC-, and botnet-equipped users. The attempts to rely on memory-intensive computations in order to remedy the disparity between architectures have resulted in slow or broken schemes”. Not being satisfied with previous attempts to solve this problem by other developers they turned their attention to the concept of asymmetric proof-of-work. They wanted to establish a blockchain the proof of which is based on a computationally hard problem, which requires a lot of memory to solve but is instant to verify. This approach was aimed to reduce the difference in the mining efficiency between the ASICs and regular computers as most ASICs did not possess a large enough amount of RAM to produce the hashing power they were intended to. Their development resulted in Equihash - a memory hard algorithm that was suitable for mining by ordinary PCs with a GPU RAM a little higher than average and was not suitable for ASIC. However, in early summer of 2018, Chinese ASIC manufacturer Bitmain managed to optimize the processing of Equihash with an ASIC. The research of the Zcash Foundation and the scientists from the University of Luxembourg stated that around 30% of Equihash hashrate is currently produced by ASIC miners.
How it works
In order to build an asymmetric blockchain Equihash developers needed to find a problem that is well-studied (to protect the network from new solutions, that were not taken into account by algo developers) and demanding on computing power. This problem was found in generalized birthday problem of probability theory. Biryukov and Khovratovich took an algorithm that was designed for the birthday problem solving by David Wagner of the University of California at Berkeley. Due to this algorithm, any strain that is took off memory reduction increases the time complexity. This means that mining’s efficiency is strongly dependent on the amount of RAM involved. Cryptocurrencies that are based on the similar principle are often referred to as memory-orientated or memory-hard. It means that the mining efficiency is predominantly determined by how much RAM is in possession of the miner.
However, Wagner’s algorithm was modified as it’s initial version allows the production of multiple solutions for the problem. This property makes mining too easy for miners with a lot of RAM as every of this solutions can be accepted by the network. For Equihash it was updated with the implementation of the technique called algorithm binding. Algorithm binding changes the problem in order for it to have not more than two solutions produced on average to make them almost unique.
Equihash can be efficiently mined with an ordinary modern PC. The only requirement of Equihash-based coins for your equipment is to have at least 2GB of RAM per one Graphics Processing Unit(GPU). However, some Equihash-based networks are already under a strain of ASICs that reduces the profitability of mining. If you do not possess an ASIC, the best option for the mining of Equihash-based coins is to use NVidia GPUs. Still, efficient AMD GPU also can maintain a profitable mining. It is very important to check the drivers of your equipment and to install the latest version of them. After that you should download a client of the cryptocurrency that you intend to mine. It is also an option to use a hardware wallet like Ledger Nano S, Trezor or other wallet that supports your crypto or to mine directly to the wallet in cryptocurrency exchange. All these methods have their pros and cons so you should research them before making a choice. You can check available mining options on the web pages and social media of the crypto, for example - ZCash community has its list of mining software with the instructions on usage. Various Equihash cryptocurrencies have different hashrate. Some cryptos can be effectively mined solo and some of them, especially the most popular ones, are only efficiently mined by mining pools.
The most famous and popular Equihash-based coin is ZCash (ZEC) that has a market capitalization of $571,879,997 according to CoinMarketCap.com on the day of writing the article. Other popular implementations of Equihash are Komodo (KMD) ($133,797,621) and Bitcoin Gold (BTG) ($459,400,614). Equihash is also implemented in the following cryptos:
- ZenCash (ZEN)
- ZClassic (ZCL)
- Bitcoin Private (BTCP)
- MinexCoin (MNX)
- BitcoinZ (BTCZ)
- Hush (HUSH)
- PirateChain (ARRR)
- Equihash: Asymmetric Proof-of-Work Based on the Generalized Birthday Problem (Full version)
- CryptoLUX Wiki (Wikipedia of University of Luxembourg: Equihash
- David Wagner - A Generalized Birthday Problem (Extended Abstract)
- ZCash company blog: Why Equihash?
- Dölle, Mirko - End of the graphics card era: 8,000 ASIC Miners for Zcash, Bitcoin Gold & Co. (In German)
- 99 Bitcoins: Zcash Mining Guide for Beginners – Mine Zcash on Your PC
- news.bitcoin.com: Study Reveals ASIC Miners Represent 30% of the Equihash Mining Hashrate
- Wikipedia: Birthday problem
- Mycryptopedia: Equihash Algorithm Explained