Proof of Activity (PoAc)

Proof of Active Consensus (PoAc) is a hybrid consensus mechanism that integrates both resource-based and economy-based principles. It leverages aspects of Proof of Work (PoW) and Proof of Stake (PoS) to generate new blocks through a two-phase process.

In the first phase, PoAc employs PoW, where miners compete to solve complex mathematical problems. These miners strive to be the first to resolve these problems and claim a reward. Unlike traditional PoW, the blocks generated during this phase are not transaction-containing but serve as templates with mining reward addresses and header information.

Following the completion of mining, the process transitions to the second phase, which utilizes PoS. In this phase, the header information of the mined block is used to randomly select a group of validators. These validators, who are coin holders with substantial stakes, are chosen based on their stake size—those with higher stakes have a greater chance of being selected. The block is considered valid and added to the blockchain only once it is signed by all elected validators. If a block fails to receive signatures from the required validators, it is discarded as incomplete. This process continues until a block is successfully signed by all required validators. The rewards are then distributed between the winning miner and the validators who signed the block.

Applications: The PoAc mechanism is employed by projects such as Decred, Espers, and Coinbureau.

Advantages:

• Security: Introducing a manipulated block into the network is difficult, as the block must be signed by all elected validators to be accepted. Unsigned blocks are discarded, enhancing the network's security.

Disadvantages:

• Resource Intensity: The PoW phase requires significant computational power, making PoAc resource-intensive.

• Wealth Concentration: Validators with higher stakes have a greater likelihood of participating in the consensus process, which can concentrate power among wealthier participants.