Proof-of-stake is designed to reduce network congestion and environmental sustainability concerns surrounding the proof-of-work (PoW) protocol. Proof-of-work is a competitive approach to verifying transactions, which naturally encourages people to look for ways to gain an advantage, especially since monetary value is involved.
Bitcoin miners earn Bitcoin by verifying transactions and blocks. However, they pay their operating expenses like electricity and rent with fiat currency. What's really happening then is that miners are exchanging energy for cryptocurrency, which causes PoW mining to use as much energy as some small countries.4
The PoS mechanism seeks to solve these problems by effectively substituting staking for computational power, whereby an individual's mining ability is randomized by the network. This means there should be a drastic reduction in energy consumption since miners can no longer rely on massive farms of single-purpose hardware to gain an advantage.
Long touted as a threat for cryptocurrency fans, the 51% attack is a concern when PoS is used, but there is doubt it will occur. Under PoW, a 51% attack is when an entity controls more than 50% of the miners in a network and uses that majority to alter the blockchain. In PoS, a group or individual would have to own 51% of the staked cryptocurrency.
It's very expensive to control 51% of staked cryptocurrency. Under Ethereum's PoS, if a 51% attack occurred, the honest validators in the network could vote to disregard the altered blockchain and burn the offender(s) staked ETH. This incentivizes validators to act in good faith to benefit the cryptocurrency and the network.1
Most other security features of PoS are not advertised, as this might create an opportunity to circumvent security measures. However, most PoS systems have extra security features in place that add to the inherent security behind blockchains and PoS mechanisms.1
Proof of Stake (POS) uses randomly selected validators to confirm transactions and create new blocks. Proof of Work (POW) uses a competitive validation method to confirm transactions and add new blocks to the blockchain.
Proof-of-stake is a consensus mechanism where cryptocurrency validators share the task of validating transactions. There are currently no certificates issued.
Proof of Stake (POS) is a built-in consensus mechanism used by a blockchain network. It cannot be earned, but you can help secure a network and earn rewards by using a cryptocurrency client that participates in PoS validating or becoming a validator.6