Statement Regarding Ethereum Classic Chain Reorganization

The Ethereum Classic network underwent a chain reorganization last night as a result of an attack on the network. The issue has been resolved. We are providing this information so that the ETC community and stakeholders have accurate information. We continue to investigate the issue, and we will provide more information as it becomes available.

Recommendation:

If you operate an Ethereum Classic node, only use the following clients:

• Core-geth
• Hyperledger Besu

What happened?

OpenEthereum/Parity and Open-ETC no longer function properly due to an unidentified bug. The bug caused a temporary and minority chain split. In the future, any Ethereum Classic node operating OpenEthereum or Open-ETC could result in mining the incorrect chain.

The miner 0x75d1e5477f1fdaad6e0e3d433ab69b08c482f14e mined ~3500 blocks offline or ~12 hours. When the miner came online it caused a large chain reorg starting at block 10904147–10907761. OpenEthereum/Parity nodes were unable to handle the large chain reorganization causing them to go out-of-sync from the network. The correct chain continued with the ~3500 block reorg. The status of the nodes can be found here https://etcnodes.org/phoenix

Is the Network Secure?

Yes. The majority chain is operating as normal. The mining pool that was mining the incorrect chain has migrated to Core Geth and has synced with the network.

Possible impact & what to do.

• Nodes: Core-geth or Hyperledger Besu
• Miners: Continue mining as the Proof of Work has chosen the chain with the large chain reorganization.
• Users/ Services: If you have any transactions during July 31st — August 1st, then please verify those transaction were correct.
• Please verify transactions within blocks 10904147–10907761.

For additional information, please contact: ETC Core.

Other resources: https://hackmd.io/@cUBb4hAvQciAEPoU2yfrzQ/Skd4X6MZw