The Stacking implementation is still in development and could change in the coming weeks
Stacking rewards Stacks (STX) token holders with bitcoin for providing a valuable service to the network by locking up their tokens for a certain time.
Stacking is a built-in action, required by the "proof-of-transfer" (PoX) mechanism. The PoX mechanism is executed by every miner on the Stacks 2.0 network.
The Stacking mechanism can be presented as a flow of actions:
- Make API calls to get details about the upcoming reward cycle
- For a specific Stacks account, confirm eligibility
- Confirm the BTC reward address and the lockup duration
- The transaction is broadcasted and the Stacks (STX) tokens will be locked-up
- The Stacking mechanism executes reward cycles and sends out rewards to the set BTC reward address
- During the lockup period, details about unlocking timing, rewards and more can be obtained
- Once the lockup period is passed, the tokens are released and accessible again
- Display reward history, including details like earnings for previous reward cycles
If you would like to implement this flow in your own wallet, exchange, or any other application, please have a look at this tutorial:
PoX mining is a modification of Proof-of-Burn (PoB) mining, where instead of destroying the committed Bitcoin, it is transferred to eligible Stacks (STX) holders that participate in the Stacking protocol.
A PoX miner can only receive newly-minted Stacks (STX) tokens when they transfer bitcoin to eligible owners of Stacks (STX) tokens
Miners have to run a software (mining client, aka "miner") on their machines to participate in the PoX mechanism. The mining client implements the PoX mechanism, which ensures proper handling and incentives through four key phases:
- Registration: Miners register for a future election by sending consensus data to the network
- Commitment: Registered miners transfer bitcoin to participate in the election. Committed bitcoin are sent to a set eligible Stacks (STX) tokens holders
- Election: A verifiable random function chooses one miner to write a new block on the Stacks blockchain
- Assembly: The elected miner writes the new block and collects rewards in form of new Stacks (STX) tokens
Stacks (STX) token holders do not automatically receive Stacking rewards. Instead, they must:
- Commit to participation before a reward cycle begins
- Hold ~94.000 Stacks (STX) tokens
- Lock up Stacks (STX) tokens for a specified period
- Set a Bitcoin address to receive rewards
Token holders will have to use software like apps, exchanges, or wallets that support participation in Stacking.
Stacking is a built-in capability of PoX and is realized through a set of actions on the Stacks 2.0 network. The full implementation details can be found in SIP-007. Below is a summary of the most relevant actions of the algorithm.
- Progression in Stacking consensus happens over reward cycles (with a fixed length). In each reward cycle, a set of Bitcoin addresses are iterated over
- A reward cycle consists of two phases: prepare and reward
- During the prepare phase, miners decide on an anchor block and a reward set. Mining any descendant forks of the anchor block requires transferring mining funds to the appropriate reward addresses. The reward set is the set of Bitcoin addresses which will receive funds in the reward cycle
- Miners register as leader candidates for a future election by sending a key transaction that burns cryptocurrency (proof-of-burn). The transaction also registers the leader's preferred chain tip (must be a descendant of the anchor block) and commitment of funds to 2 addresses from the reward set
- Token holders register for the next rewards cycle by broadcasting a signed message that locks up associated Stacks (STX) tokens for a protocol-specified lockup period, specifies a Bitcoin address to receive the funds, and votes on a Stacks chain tip
- Multiple leaders can commit to the same chain tip. The leader that wins the election and the peers who also burn for that leader collectively share the reward, proportional to how much each one burned
- Token holders' locked up tokens automatically unlock as soon as the lockup period is completed
Check out the Stacking contract reference to see available methods and error codes.