The respected computer scientist Dahlia Malkhi criticized the upcoming Proof of Stake (PoS) system at Ethereum called Casper. She is enthusiastic about crypto currencies, but there is too little academic research on the security of protocols like Casper.
From Proof of Work to Proof of Bitcoin profit
The Proof of Work (PoW) system is effective when it comes to securing a Bitcoin profit network, but it requires a lot of power and thus pollutes the environment. Bitcoin profit mining will soon require as much electricity as Argentina, i.e. almost 140 terawatt hours or 0.6 percent of the world’s energy supply.
Proof of Stake is a solution to the energy problem. The PoS system secures the network by allowing participants to „stake“ their coins. As soon as a user „sets“ the digital currency, he has the opportunity to find the next block and receive a reward for doing so. The more digital coins you bet, the more likely you are to find the next block.
Proof of Stake – The vulnerabilities
The approach sounds tempting and easy to implement. In practice, however, there are several problems. The biggest problem is the „Nothing at Stake“ problem. Suppose someone wants to attack the Bitcoin network. This person needs enough equipment to generate 51 percent of the future blocks. Nowadays this is more than unlikely. Miners also have to pay for their hardware, electricity and storage costs. This always gives them an incentive to mine the right blockchain and earn money.
The person is annoyed by Bitcoin and now chooses a PoS system. He first buys a large part of the coins and sets them to create fake new blocks. Other, honest Staker would lose nothing now, if they would create the right and wrong blocks. Because the stackers can stack on both blockchains at the same time and get more money.
The problem was deliberately kept simple and explained, the following video goes into more detail about the „Nothing at Stake“ problem:
Casper as a solution?
Ethereum tries to solve this problem with a system called Casper. Casper, Ethereum’s PoS system, is designed to punish those who generate a new blockchain.
Ethereum’s PoS system requires a certain amount of ether to validate transactions. If the Ethereum network now believes that a staker is lying or generating false data, part of the staker’s ether will be confiscated from the network. This creates an incentive to stay on the right blockchain.