09/14 - Project PAI Hybrid Consensus Hard Fork




The Project PAI Blockchain will fork to a new PoW/PoS Hybrid Consensus mechanism using an alternative, SHA-3/SHAKE-256 hashing algorithm. This hard fork is mandatory, non-backwards compatible, and there are no provisions for a separate “Original PAI” to continue.

Updating to the new version is as simple as rebuilding paicoind using the 2.0.001 tag from the official repository. See here: https://github.com/projectpai/paicoin/tags. The hard fork will begin taking effect at a target block height which will be announced soon. Once your node is updated, no further intervention should be required. All existing RPC/CLI commands and usage will remain the same, though some new commands will have been added.


Following recommendations set out by the research paper, Prospective Hybrid Consensus for Project PAI, Project PAI Core Developers have been working on a “Hybrid” Proof of Work/Proof of Stake consensus mechanism for the next iteration of the PAI Blockchain. The primary goals of this fork are to:

  1. Remove the current whitelist that prevents the public from mining freely. The whitelist was originally implemented to disincentivize 51% attacks and other malicious activity. These vulnerabilities will be alleviated by the PoS portion of the Hybrid implementation.
  2. Move away from hashing functions known to be supported by ASIC devices, thereby reducing the barrier to entry for mining. This will theoretically enable greater participation in mining.


The execution of this hard fork is set to begin for:

  • Testnet at block height: 78,600
  • Mainnet at a block height TBD

After the forking block height, the blockchain will enter an Interim Transition Period (ITP). During the ITP, it will be possible to purchase Stake Vouchers (SVs), but the SVs will only become eligible to vote once the ITP concludes. More information on how to purchase SVs, as well as the duration of the Interim Transition Period will be announced soon. Once the ITP concludes, votes will be required to approve any new blocks and the mining whitelist will be removed, thus enabling full PoS protection.


What you need to do in preparation for this Hard Fork depends on how you use PAI Coin.

Full Node

If you run a full node (which you would be doing if you are running paicoind from the official Project PAI GitHub repository), you will need to update your PAI Coin software prior to the fork. If you do not, your node will stop functioning properly after the fork. Fortunately, updating should be straightforward.

You simply need to:

  1. Update the local version of your paicoin codebase to tag 2.0.001
  2. Build paicoind per the instructions in doc/build_unix.md

Once complete, you should be able to verify you are on the correct version by executing:

paicoind --version

And you should see:

PAIcoin Core Daemon version v2.0.001-[build]

Note that the dependencies and build requirements for paicoind have not changed with this release. Likewise, all currently available RPC/CLI operations for paicoind are still present and fully backward compatible. Some new commands have been added.

PAI Up Mobile

You will need to update your PAI Up Mobile app prior to the fork in order to continue using it. The newest version for Android will be available for download from https://paiup.com. A safe and straightforward distribution mechanism for iOS is being researched and will be announced soon. We strongly encourage you to write down your paper key (12-word seed phrase) before updating PAI Up. This will ensure you do not lose access to your wallet and coins if something goes wrong during the update.

PAI Up Web

No changes are necessary. However, the PAI Up Web Wallet will be inaccessible for several hours before and after the fork execution until stability of the post-fork blockchain is confirmed.

PAI Coin Pool

No changes are necessary. However, PAI Coin Pool deposits and withdrawals will be disabled for several hours before and after the fork execution until stability of the post-fork blockchain is confirmed.

Huobi and other exchanges

If you are a user of Huobi Global, or other platforms that exchange PAI Coin, please pay attention to their latest information. It is conventional that they will disable deposits and withdrawals for a period before and after the fork execution.


We are very excited to finally make the work we have been doing on this version of PAI, public. We believe that it will position PAI for a long and fruitful future. Thank you for your continued support in making Project PAI a success!

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