Discovering Atlantis: Ethereum Classic Hard Fork and What Will Change

On June 19, the Ethereum Classic (ETC) community announced that the Atlantis hard fork is now in its testing stage. As Cointelegraph previously reported, the update is scheduled for September and will take place on the block 8.75 million.

Also, as Cointelegraph reported, ETC Labs, which actively contributed to the Atlantis project, has recently launched an Ether (ETH)/ETC interoperability tool as part of the Metronome Validator Network software. This move brings transparency on certain aspects of the upcoming upgrade.

ETC itself was introduced after the DAO attack back in 2016, when 3.6 million ETH had been stolen within the first few hours. At the time, it was equal to $70 million. To reverse the malicious transactions, Ethereum hard forked and thus gave birth to Ethereum Classic. At present, ETC is the 20th-biggest cryptocurrency, as its market capitalization of over $865 million, according to However, let’s take a deeper look at the motivations, technicalities and potential consequences of the hard fork. 

Ethereum Classic all-time chart

Ethereum Classic all-time chart. Source:

Why the hard forking?

A hard fork is a radical change to a protocol of a blockchain, which can be carried out to reverse transactions, add new functionality or fix security risks. Unlike the previous time when the DAO was attacked, the hard fork is more of a beneficial renewal rather than a necessary measure. According to the blog post of Ethereum Classic Labs, the upcoming hard fork is aimed at presenting secure high-quality blockchain software while taking into account the community’s concerns. 

Atlantis is a consistent, no-rush update that would ensure compatibility of ETC with Ethereum, leading to an easier collaboration of sibling blockchains. The team also intends to improve the functionality and stability of ETC. The last point is especially relevant, as the network had experienced a “51% attack” last January. 

Who is involved? 

In order to complete the technical development of the main client, Classic Geth (which 68% of the network uses), ETC Labs has collaborated with ChainSafe Systems and cooperated with ECC, Parity and IOHK. A team of developers, ETC Labs Core, who are believed to be among the most skillful, has actively contributed to Multi-Geth preparation. As for ETC Labs’ blog post, “The ETC community has shown great attention to and support” for the hard fork. “All stakeholders have fully participated in the discussions on the details, scope, and timing of the hard fork,” the developers said.

ETC Labs and Metronome will deploy a cryptocurrency named MET, which will be transferable between the blockchains. This is possible because “chainhopping” is a property of the blockchain asset and can be transferred from one chain to another. According to the blog post, “ETC Labs will support Metronome’s Validator Network to ensure reliable and secure transaction verification that guards against double-spend attacks and provides fluid cross-chain transactions.” Terry Culver, ETC Labs’ CEO, wrote in the Medium post: “We are excited to work with the Metronome team to help initiate its Validator Network, which will first enable movement of Metronome tokens between Ethereum and Ethereum Classic.”

Reaching consensus on schedule 

On June 11, after an intermediate scheduling call, stakeholders from North America, Europe, and Asia agreed upon the hard fork’s timetable: It was decided that ETC Kotti and ETC Morden testnets would be activated at blocks number 716,617 and 4,729,274 respectively, and finally the hard fork would be implemented at block 8,500,000.

Ethereum Classic

However, bearing in mind that the chosen block would run on a Sunday, ETC Labs adjusted the schedule during Ethereum Classic Improvement Protocol (ECIP) finalization call on June 20. ETC Labs announced that the hard fork would then be set to occur on block height number 8,772,000 (which will be hit on Tuesday, Sept. 17, around noon UCT) to have more parties involved in implementation. 

The decision was unanimous, and the deadline of the release seems rock-solid, according to a statement from ETC Labs to Cointelegraph:

“The community has had a number of meetings to discuss timing, scope and involvement, and we have decided on the direction and timing of the Atlantis release. So, the decision was made and the community and stakeholders are all moving forward.” 

What do we know about Atlantis?

Atlantis is there to incorporate multiple Ethereum Improvement Proposals (EIPs) that have been around on Ethereum for some years already. The mission of the hard fork is to pull ETC up to ETH’s latest protocol enabling easier interoperability between them. 

ETC Labs Core described some of the features of ECIP-1054 (Atlantis) in their blog post, explaining what exactly the community should be expecting. 

Overall, the update consists of 10 improvement proposals including improvements to stability, op-code upgrades, precompiled contracts to improve zkSNARKs, performance-related improvements and enhanced security. 

Zero-Knowledge Succinct Non-Interactive Argument of Knowledge (zkSNARK) is the core of ECIP-1054. What hides behind the spooky title is a familiar zero-knowledge proof. It implies that no interaction between prover and verifier is needed, which “allows one to prove x without having to convey any information to the verifier other than they know x.” 

Сustomary encryption schemes efficiently secure data but need to be decrypted before computation. To change that, zkSNARK uses the Homomorphic Encryption technology that allows computations on encrypted data requiring no special access: The prover and verifier only share a dataset or parameters of the encryption. 

Further, by updating to zkSNARK, users obtain increased privacy necessary for data such as identity or location, which is now totally transparent on the blockchain. This feature is based on EIP-196. As for its description, zkSNARKs could in theory be implemented by Ethereum Virtual Machine, yet they would not fit the block gas limit due to the cost. 

EIP-196, for its part, suggests to adjust certain parameters of znSNARK so that the technology would perform effectively at a reduced gas cost. Meanwhile, EIP-197 ensures the verification of zkSNARK contracts on the Ethereum Classic blockchain. The EIPs make the technology flexible enough to be further improved and advanced without another hard fork.

Among the benefits that the update poses, there will be a more predictable ETC issuance rate. The current formula lacks the “uncle rate,” which will be fixed by EIP-100 (“Change difficulty adjustment to target mean block time including uncles”). Furthermore, deployment of a decentralized application (DApp) after the hard fork, as well as migration of DApps between Ethereum and Ethereum Classic, will become easier and more efficient. 

The community can also expect a better performance of Ethereum Classic, as