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Ethash is the proof-of-work function in Ethereum-based blockchain currencies.[1] It uses Keccak, a hash function eventually standardized to SHA-3. These two are different, and should not be confused. Since version 1.0, Ethash has been designed to be ASIC-resistant via memory-hardness (harder to implement in special ASIC chips) and easily verifiable.[2] It also uses a slightly modified version of earlier Dagger[3] and Hashimoto[4] hashes to remove computational overhead.[1][5] Previously referred to as Dagger-Hashimoto, the Ethash function has evolved over time. Ethash uses an initial 1 GB dataset known as the Ethash DAG and a 16 MB cache for light clients to hold. These are regenerated every 30,000 blocks, known as an epoch. Miners grab slices of the DAG to generate mix-hashes using transaction and receipt data, along with a cryptographic nonce to generate a hash below a dynamic target difficulty.[1]

ASIC Miner Controversy[edit]

In April 2018, the first ASIC miners for Ethash, the ASIC-resistant hash, were announced by Bitmain.[6] Fear of over-influence from Bitmain and 51% attacks prompted discussions of bricking the devices, [7][8] forcing ASIC miners into hard-mode mining, or continuing or expediting development and eventual release of Casper. It is thought that ASIC miners are not a threat to Ethereum.[9] It was decided that Ethereum would switch from its pure proof of work to a hybrid proof of work and proof of stake scheme.[10][11]


  1. ^ a b c "wiki: The Ethereum Wiki". 8 February 2018. Retrieved 8 February 2018 – via GitHub.
  2. ^ Rudlang, Marit (Jun 2017). Comparative Analysis of Bitcoin and Ethereum (PDF). Norway: NTNU: Norwegian University of Science and Technology. pp. 52–53. Retrieved 29 September 2018.
  3. ^ Vitalik Buterin. Dagger: A memory-hard to compute, memory-easy to verify scrypt alternative. Tech Report, website, 2013.
  4. ^ Dryja, Thaddeus. "Hashimoto: I/O bound proof of work" (PDF). Semantic Scholar. Archived from the original (PDF) on 2017-08-10.
  5. ^ Tikhomirov, Sergei (17 Feb 2018). "Ethereum: State of Knowledge and Research Perspectives" (PDF). International Symposium on Foundations and Practice of Security (FPS 2017): 206–221. Retrieved 29 September 2018.
  6. ^ Havervold, Kale (3 Apr 2018). "Bitmain Announces 1st Ethash Asic For Ether Mining". Coin Journal. Retrieved 30 September 2018.
  7. ^ "Ethereum Developer Opens EIP to Discuss 'Bricking' Ethash ASIC Miners". CCN. 30 Mar 2018. Retrieved 30 September 2018.
  8. ^ Stanfill, David (3 Apr 2018). "EIP 969: Modifications to ethash to invalidate existing dedicated hardware implementations". Ethereum Improvement Proposals. Retrieved 30 September 2018.
  9. ^ Moos, Mitchell (19 Apr 2018). "Vitalik Buterin: Ethash ASICs Not a Threat to Ethereum". CryptoSlate. Retrieved 30 September 2018.
  10. ^ Sanders, Gregory (29 Mar 2018). "Casper Version 1 Implementation Guide". GitHub. Retrieved 30 September 2018.
  11. ^ Jagati, Shiraz (22 Apr 2018). "Ethereum's Proof of Stake Protocol Under Review". CryptoSlate. Retrieved 30 September 2018.