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⚠️ NOTE: Action Required before Nov/29 2020! ⚠️

  • ⚠️ Ethereum Classic miners: upgrade your mining software to one of the miners listed below.
  • ⚠️ Ethereum Classic pools: upgrade your pool software to open-etc-pool or manually integrate etchash modules.
  • ⚠️ Ethereum Classic nodes: upgrade your ETC client software to latest Core-Geth or Hyperledger Besu.


etchash is the modified dagger hashimoto used by ethereum classic. it is comparable in it's behaviour to ethereum foundation's ethash but allows for a long-term viability of gpu-mining with cards that have low memory (3gb, 4gb, 6gb) available. this repository contains an overview of the specification, and tries to point to existing implementations of clients, pools, miners, and other tooling relevant for etchash.


etchash was first brought up and specified by luke williams (@iquidus) in september 2020. the full specifcation can be found in ecip-1099: calibrate epoch duration. the idea is to calibrate the epoch length used in dag calculations, effectively doubling epoch durations and therefore reducing the dag size significantly and slowing down dag growth drastically.

it was used to replace the old specification ecip-1043: fixed dag limit restriction published by cody burns (@realcodywburns) and wolf spraul (@wolf-linzhi) in april 2018. additional etchash test cases can be found here: ecip-1099-data.

Networks powered by EtcHash

ethereum classic transitions from ethash to etchash on block 11_700_000 (eth/64 forkid 0xdb63a1ca) which marks the epoch boundary 390 --> 195 according to the specification. the estimated activation date is expected to happen around december 2nd, 2020.

the mordor classic testnet already transitioned from ethash to etchash on block 2_520_000 (eth/64 forkid 0x66b5c286) which marked the epoch boundary 84 --> 42 on october 18th, 2020.

the hard-fork activating etchash on the ethereum classic networks is code-named thanos upgrade, etchash fork, or ecip-1099 transition.

Clients implementing EtcHash

core geth v1.11.18 or later

hyperledger besu 20.10.0-RC2 or later

stand-alone go-language etchash implemenation

Mining Software Support

⚠️ Are you a miner? Check out BBT's YouTube intro "Ethereum Classic Hard Fork - Thanos - Important for Miners" or 2miners blog post "Ethereum Classic Hard Fork to Change Cryptocurrency Mining Algorithm. How to Keep Mining ETC?".

open source:

  • ethminer/etcminer (🕚 unpublished)


Mining Pool Software Support

Public Testing Pools for EtcHash

Mordor testnet: ⚠️ No payouts!

API: (or /api)
Stratum: (Nicehash)

Classic mainnet: ⚠️ No payouts!

API: (or /api)
Stratum: (Nicehash)


The modified Dagger Hashimoto used by Ethereum Classic.







Contributors 4