CAHF: A contingency plan against Byzantium HF & POS Change(EIP649)


Released WETH client for Ethereum Vega network! https://github.com/EthereumVega/weth/releases/tag/1.8.2 More info coming soon..


HF: ‘HF’ stands for Hardfork. Developers add a mandatory rule set to change the node software. These changes make previously invalid blocks become valid. Nodes/Miners with the rule set changes will follow this chain if they have a consensus.

CAHF: ‘CAHF’ stands for Community Activated Hard Fork. Like HF, developers add a mandatory rule set to change the node software and these changes make previously invalid blocks become valid. The CAHF proposal is a peaceful and voluntary departure of different community members who have different opinions or visions, and it is not intended to make an attack against other blockchain(s), even if the CAHF chain has the higher hash rate or higher value.

Byzantium HF: ‘Byzantium Hardfork’ is a hard fork will be occurred to post-chain (called Main-net Homestead chain). It contains EIP649 and will be the bedrock of POS(Proof-of-Stake) change.

POW: ‘POW’ stands for Proof-of-work function. A chain or network using POW may consume a lot of energy resources but has an effective, sustainable security system.

POS: ‘POS’ stands for Proof-of-stake function. A chain or network using POS may consume less energy than POW but may have security risk and less circulation on tokens.

EIP649 node: An Ethereum node that has implemented EIP649 consensus rule changes.

EIP649 chain: A blockchain that is valid according to the EIP649 consensus rule changes.

Original chain(Homestead): The blockchain that uses the same consensus rules in use today.

Circulating Supply(Homestead): Circulating Supply (or total amount of newly issued ether by mining & pre-sale) of Ethereum Main-net. Now circulating supply is approx. 94 million ether.


Like all Ethereum user knows, Ethereum has passed over several hard forks. Several HF that have initiated to Ethereum main-net caused several consensuses between Ethereum foundation, miners and community. Despite that changes of main-net consensus and protocol updates maintained Ethereum’s inherent value, however, all hard forks weren’t able to pull all user’s agreement. For example, hardfork that contains refund of The DAO hack occurred chain split to the one’s who did not updated their protocol (Known as Ethereum-Classic chain) and the hard forked chain (Now the main-net of Ethereum)

After 1 year later of the chain split, Ethereum’s main-net has been scheduled to change to Metropolis, therefore main-net chain may pass 2 Hardforks called Byzantium and Constantinople hard fork. Before the hard fork, main-net chain’s mean block time has been increased due to an extreme difficulty increase by a code called Difficulty-Bomb code. It’s code’s purpose was to give an incentive when main-net hardforks, eventually abandon original chain.

In order to delay the difficulty bomb, Ethereum Foundation and their dev team has decided to change the codes on Byzantium(EIP649). Meanwhile, they are also changing mining issuance 5 to 3 as they are saying since the mean of the block time has decreased total issuance of mining may have kept the same until Ethereum’s POS change.

The start of necessity of issuance reduction was started from single anonymous individuals, claiming that reduction is needed for reducing the incentives for miners and reducing inflation, eventually cause POS change and it would be more “greener” Ethereum (see https://github.com/Ethereum/EIPs/issues/186).

However, EIP649 including issuance reduction poses a significant risk for the Ethereum ecosystem, so we are preparing a contingency plan to protect the economic activity on the Ethereum blockchain from this threat.

The purpose of this blog post is to announce our CAHF contingency plan for EIP649/Metropolis.

Why we need a contingency plan against EIP649 and POS change

Late September, The Byzantium hard fork including EIP649 will trigger chain split and will be adopted at higher chances.

EIP649 is very dangerous for Ethereum ecosystem including users and miners. Smaller incentives for mining is equal to smaller payment for security of main chain, and the risk of security caused from decrease of mining hashes may grow up higher. Since miners won’t spend their energy or equipment to smaller intensive, they would likely move to another chain before POS change. Therefore, the mining activity behind a Byzantium chain may stop without notice, and investors who bought in the EIP649 propaganda may lose all their investment. Any exchanges that decide to support a Byzantium token after the forking point need to consider the stagnation risk attached to it.

Also decreasing supplement of ether without POS may cause serious economic problem based on “unplanned” supply such as deflation or other arguments from investors, eventually make investors reconsider their investing activity to Ethereum.

Furthermore, We, the Ethereum holders or miners has a right and ‘duty’ to ‘capture’ or ‘preserve’ our investigation which is the main-net of Ethereum against the risk, we should build a contingency plan for our original chain being attack.

Protection Plan

This plan is for Community Activated Hard Fork, or CAHF. You can find technical specs here: https://github.com/CAHF/Ethereum-CAHF

CAHF will be activated “right before” Byzantium HF. We will update the specific time ASAP when the blockstamp of Byzantium hardfork is updated.

CAHF chain will follow and fork existing rules of the Ethereum’s main-chain, except for issuance reduction and POS. We will maintain our POW chain which will be the Ethereum-POW chain (when Ethereum hardforks to POS).

Once we check that there is no further problem on the chain, we will make our repository ‘public’ and release our CAHF geth node. (Will be updated to our twitter account)

We share the same belief with some very early Ethereumers, that decentralization means that more than 1 billion people in 200 countries are using Ethereum as a saving currency and payment network, which comprises of hundreds of thousands of Ethereum services, traders, exchanges and software to be decentralized. We do not believe that decentralization means a decrease of issuance so there will be no more inflation before POS change or change to POS so some accounts that has larger volume of Ethereum takes most of issuance than who doesn’t.

Software development

Currently, there are at least 4 client development teams working on the code of the spec. All of them want to stay quiet and away from the propaganda and troll army of certain companies. They will announce themselves when they feel ready for it. Users will be able to install the software and decide whether to join the CAHF.

The software is expected to be ready before late September, and it will be live on testnet by then.


For other parties in the ecosystem, we recommend detailed research on effects of the EIP649. All Ethereum businesses must be prepared on that day to mitigate or eliminate the risks that EIP649 carries.

  1. https://blog.bitmain.com/en/uahf-contingency-plan-uasf-bip148/
  2. https://github.com/digitsu/splitting-bitcoin
  3. http://www.uasf.co/
  4. https://github.com/ethereum/EIPs/issues/186#issuecomment-269902119
  5. https://github.com/ethereum/go-ethereum/pull/15028/commits/b872961ec82ec88a7ac6ef331cfb3eb685ce2c00