CKB Testnet Mining Competition Round 3:Earn 6,000,000 CKB here, and GPU miner is ready to have fun!

With the second round of the Nervos CKB mining competition complete, we want to express our sincere gratitude to the community, and all that participated. Not only did this second round help us further stress test the network and provide valuable data and insights, but the community also helped us identify a bug in the difficulty adjustment which is now being fixed!

We would like to remind our community that the proof-of-work testnet is still a “wild-west” with all sorts of craziness — being of course very different from how CKB and other mainnets like Bitcoin operate. These unexpected dynamics that sometimes can not be predicted theoretically, is exactly what the testnet is for.

To reward our community for participating in the construction of Nervos CKB, the Nervos Foundation is sponsoring the third round of the CKB testnet mining competition! Anyone can participate in the testnet mining, and potentially win a total of 6 million mainnet CKB tokens. Please join our Telegram(EN) if you have any questions.

We just released the Cuckoo GPU miner (Nvidia GPU only) for our testnet! Although it’s simple and has not been fully tested yet, but everyone with GPU can just have fun using this GPU miner. For more detail please check GitHub.

But please note that for now Nervos team is working on Layer 1 CKB, as our time and energy is limited, the GPU miner is only for Nvidia GPU. Nervos team has no preference over Nvidia or AMD GPU.

Also we’ve released avx512 miner, which can improve CPU mining performance, for more detail you can check GitHub .

After the second round of our mining competition, we released RFC (Request for Comment) on our forum to ready us for the third round. We gathered comments from our community members and adapted the rules as follows:

Reward distribution

The community pool rewards (3,000,000 CKB)

All addresses that have mined at least 3,000 CKB testnet token will share this reward pool and receive CKB rewards in proportion with the block rewards produced by each address.

The lucky block rewards (3,000,000 CKB in total, 80 winners)

On the current Nervos CKB testnet, there is one difficulty adjustment epoch in about every four hours. We expect there will be 84 epochs in total during the two weeks’ mining competition based on what we saw in the mining competition phase 1. From Epoch 1 to Epoch 80, any address that mined the first block aka lucky block in each epoch will be rewarded 37,500 CKB. Note the genesis Epoch (Epoch 0) is not included.


Start: August 10 6:00 AM (UTC) UNIX Timestamp: 1565416800
End: August 24 6:00 AM (UTC) UNIX Timestamp: 1566626400

Competition Process:

8.10 5:00 AM UTC, Release CKB testnet v0.18.0 in Github. ONLY using this testnet version can participate in mining competition.
8.10 6:00 AM UTC Competition begin. Blockchain explorer will be ready in two hours.
8.24 6:00 AM UTC, competition is over. We will release the result within one day on this website.

How to participate

To start mining on CKB testnet, simply follow the steps outlined in the official guide or community-created tutorials on Nervos Talk. A CKB blockchain browser is also available to look up your mining rewards.

CKB-Mine-Lord website created by our community member to show the rank of all the addresses, you can check it to get your real-time rank, here is the code of this website for your reference.

Upon the completion of the competition, we will calculate block rewards mined by each address. The accumulated block reward of each address during the competition will form a basis for CKB mainnet token rewards (testnet tokens gained by transactions will NOT be counted as block rewards).

Rewards will be distributed directly to respective addresses on CKB mainnet. Please exercise caution when managing your private key as it will be your sole means of claiming your CKB token rewards.



  • How are the block rewards in CKB different from those in Bitcoin?
    • For Bitcoin, the block rewards are fixed in each block you mine; For CKB, the total block rewards are fixed in each difficulty adjustment epoch. CKB consensus adjusts difficulty to adjust block time, when difficulty increases, there will be less blocks mined during one epoch, but block rewards in each block mined will be increased. And vice versa.
  • What is difficulty adjustment epoch in CKB?
    • On the current Nervos CKB testnet, we target difficulty adjustments at every four hours (In Bitcoin, the difficulty adjust happens every 2016 blocks, while the block interval is 10 mins). For more details please refer to our consensus RFC.
  • Why do the community pool rewards only apply to addresses that mined at least 3,000 CKB testnet token ?
    • The native token CKByte represents state storage space on the Common Knowledge Base blockchain. A cell is the basic data structure in the blockchain, and you can put any arbitrary data in a cell. It requires 60 CKBytes to create a cell.
    • During mining competition phase ONE, 105,000,000 CKB testnet token were mined, and we expect the same amount of testnet token will be mined in phase 2. Given the community pool rewards of 3000,000 CKBytes, it requires you to have at lease 2,100 CKB testnet token mined to be able to receive the 60 CKBytes rewards. We add some buffer and require at least 3,000 CKB testnet token to receive rewards.
  • When should I increase my hashrate in order to get the lucky block reward?
    • Increase the hashrate when getting closer to the start number of next epoch. You can calculate the start number of next epoch based on the current epoch start number (block height) and the length of each epoch in CKB explorer.
    • Please be aware that we have seen the “selfish mining attack” happened when miners were competing for the lucky block rewards, i.e. Miner A increased the hashrate → mined the lucky block → withdraw the hashrate, while Miner B increased the hashrate →didn’t mined the lucky block → maintain the same hashrate while Miner A withdraw its → Miner B re-org the chain and Miner A lost its lucky block.
    • Nervos Foundation reserves the right to change, amend and add new rules at any point during the competition and dis-qualify any participants who attempt to exploit, cheat or maliciously attack the test-net or competition. All decision made by Nervos Team are final.
  • After mining a block, how long does it take to receive the block rewards?
    • The block rewards from Block N will be received in Block “N + 11” (about 3 minutes) via Cell Base Transaction. This design related to our two-step transaction confirmation, if you are interested please check our consensus RFC.
  • Is Cuckoo Cycle the hash function for Nervos CKB?
    • We just use Cuckoo for our testnet. Nervos CKB’s hash function is called Eaglesong. Eaglesong is a new hash function developed specifically for Nervos CKB proof-of-work. It is also suitable in other use cases where a secure hash function is needed. The design criteria were exactly those described above — novelty, simplicity and security. For more detail please check the RFC for Eaglesong.
  • How to know the value of token?
    • There’s 33.6 billion CKBytes mainnet token in genesis block ,more info will be disclosed later.

Things to Note

  • This is the third round of competition in a series. It is possible that any future rounds will have different rules and rewards.
  • In the previous round, some rewards are distributed to null address, which may caused by entering the wrong Lock Args. So please make sure everything is right when you are configuring.
  • CKB tokens rewards will have a lock-up period of 6 months. The specific block height at which these reward tokens get unlocked will be announced prior to mainnet release.
  • Addresses for the same private key might be different on testnet and on mainnet due to difference in algorithm. Participants only need to hold on to their private key to be able to claim rewards.
  • Participation in this event means that you have read and understood the competition terms.
  • Nervos reserves the right to change, amend and add new rules at any point during the competition and dis-qualify any participants who attempt to exploit, cheat or maliciously attack the test-net or competition. All decision made by Nervos Team are final.

For more info please check our website.

1 Like