At Devcon 5, the Ethereum developers conference that took place in Osaka from October 8 to11, Ethereum’s founder Vitalik Buterin stated that after the implementation of PoS on Ethereum blockchain, it would be more difficult for the attackers to make a breach as it would be a lot more costly than any PoW backed currency.
The proof of stake model requires a user to lock his ethers (for the case of ethereum) into smart contracts in order to be eligible for validating blocks. The equivalency of having a large hashrate in PoW is staking more money in the case of PoS. A person with a higher hashrate had more probability of validating a block in PoW, similarly, a person who staked more has the same powers here. For a hacker to add blocks in the blockchain, he would have to stake a lot of money. Even after the adding of blocks, there would be a time for a challenger to check and see whether there is a sign of suspicious activity or wrong validations on the blockchain in which case he would challenge the validation and the hacker would lose all of his staked money. According to Vitalik:
The challenger can submit a transaction that points to [the block in question]. That calculation runs on the blockchain. The blockchain’s like, ‘wait the actual answer is 256 and this guy submitted 250 so this guy’s wrong.’ The original guy’s deposit is destroyed and part is given to the challenger.
For a successful attack to happen, several malicious blocks would have to be validated, which would take an enormous amount of ethers staked. The hackers would have to take an enormous amount of risk because if their attempts are caught, they’d end up losing all the ethers they staked to reach that authority. The only possibility would be when an entity as powerful as a government or someone with a whole lot of money who’d want “to see the world burn” attempts an attack on the PoS chain.
Ethereum is tentatively launching their PoS publicly early in 2020, along with Cardano. The prime advantage is considered to be the solution of the abuse of electrical power through PoW, which required high computing powers that are directly proportional to extensive electrical power being drained. So, not only will this switch make the blockchain and transactions secure, but they would also be ecofriendly. Although the integration of sharding in this new update would bring more speeds along with the existing benefits of PoS, the issue of partial centralization would still be a concern, as the consensus algorithm is not truly random. The algorithm gives more decision power, and opportunities to validate the transactions to those who have staked more ethers or those who have more resources. Until the time when true randomization is achieved, the purpose is to provide security to the chain. According to Jason Palmer, the founder of Dogecoin:
Consensus mechanisms are about aligning incentives to output a decision in the least centralized way. They are not designed to be flawless.