Proof of activity is a consensus mechanism used in decentralized blockchain networks to validate transactions. It is a hybrid approach that combines aspects of proof of work and proof of stake consensus mechanisms.
Proof of work and proof of stake are both designed to prevent 51% attacks - a malicious action in which one individual or party controls a majority of the mining power in the cryptocurrency network and can then include invalid transactions in the blockchain. Proof of activity combines these mechanisms into a single two step-process:
- Proof of work for miners to compete to find the block and earn the block reward. The greater percentage of the network's total computing power a miner has, the greater the probability that they will find a block.
- Proof of stake to validate/sign the new block. The greater the percentage of the total cryptocurrency supply a staker has, the greater the probability that they will be chosen to validate the block.
Proof of activity adds a second line of defense against 51% attacks because an attacker would theoretically need to have both 51% or more of the network's total mining power and 51% or more of the coins staked in the network in order to successfully pull off the attack.
A CryptoCoderz Team Project White Paper Written by the CryptoCoderz Team February 20 th 2018 (Version 1.0 Release)
Decred Proof of Stake
Overview - Decred Documentation
Proof of Activity Proposal
Proof of Activity: Extending Bitcoin’s Proof of Work via Proof of Stake
Iddo Bentov, Charles Lee, Alex Mizrahi, Meni Rosenfeld