28 February 2020
The validation of transactions through Proof of work (PoW) consumes a lot of computational energy and time for solving a complex cryptographic puzzle in mining, so as an alternative to this Proof of Stake (PoS) was developed. Proof of Stake (PoS) is a consensus algorithm that was initially suggested in 2011 on the Bitcointalk forum and the first cryptocurrency to implement it was Peercoin in 2012.
What is Proof of Stake (PoS)?
It is a consensus algorithm having the same work purpose as PoW of achieving distributed consensus - a system giving incentives for validating people’s transactions and maintaining integrity but the way to reach this goal is quite different. In PoS, the users who validate transactions and create new blocks are referred as Forgers and the blocks are referred as “forged” or “minted”. The selection is done on the basis of two elements. Let’s check each of them.
The first element considered is the user’s stake. Forgers (validator) in order to get a chance to verify transactions have to stake some portion of their coins or tokens. Thus, the forger holding the highest amount of coins has the highest chance of being chosen. During the transaction validation, the forger stakes his own coins which are held securely in the system. If the forger mistakenly validates a fraudulent transaction, he may lose the stake amount along with the right to participate in the forging process. However, to resume participation in the forging process, the forger has to again stake some coins. In the PoS algorithm, the incentive is always given in the form of transaction fees.
The second element is the selection method that depends on the blockchain type. The two selection methods are Randomised Block Selection and Coin Age Selection.
1. Randomized Block Selection:
The next forger is selected on the basis of a formula i.e. the combination of the lowest hash value and the highest stake. Each node in the system can predict the next forger on the basis of stake as it is public. Nxt and BlackCoin are two cryptocurrencies that use the randomized block selection method.
2. Coin Age Selection:
In this method, the forger is selected on the “coin age” of the stake amount. The coin age is calculated by multiplying the number of coins with the number of days of coins that are held as a stake. The coins should be held for a minimum of 30 days before they compete. The chance to become the next forger turns brighter when the coins are stalked for a longer time and more amount of coins. Once the user has forged the block, the coin age is reset to zero and waiting period of 30-90 days is applied. This prevents users dominance on the blockchain. Peercoin uses coin age selection process combined with a randomized selection method.
1. Energy efficient:
As PoS involves no mining process that consumes a lot of electricity.
2. No 51% attack:
It is an attack that includes a group of entities that control the maximum hashing power of a blockchain which is used for personal gains. In PoS, this attack is avoided because it an expensive process to accumulate 51% of the coin.
1. Nothing at stake issue:
It is a situation which can occur due to consensus failure due to which there is fork generation (i.e. splitting of blockchain in two) and validator is left with no option but has to support both the chains and validate the block. Due to this issue, the stake would be duplicated on both chains meaning the validators can claim twice the amount of rewards.
Proof of Stake is a protocol that determines the creator of the new block in a deterministic way depending on the wealth, effectively and efficiently fulfilling the intended purpose of achieving and maintaining a decentralised system.