Proof of Work and Proof of Stake are major blockchain consensus protocols in the blockchain. However, there are many other protocols that are employed by blockchain applications.
In this lesson we will take a look at few of them in brief.
Delegated Proof of Stake (DPoS)
In this protocol, the users of the network gets to choose a fixed number of block producers of the network. The number of votes of each network user gets to cast depends on the amount of cryptocurrency they own in the network.
Once the block producers are elected, they get to create blocks in a round robin fashion. DPoS has a better throughput than PoW, however in the process it sacrifices decentralization.
DPoS employed networks also have a mechanism where the network users can vote out a block producer who has been found to be malicious. Block finality is realized through either the longest chain rule or through a process where a block which has one more than 2/3rd of the votes cast by block producers, with the later being the first criteria of selection.
Proof of Activity (PoA)
This is a hybrid of Proof of Stake and Proof of Work. In this consensus protocol, the process starts in a Proof of Work mechanism and then switches to Proof of Stack.
Miners race to solve the puzzle similar to the PoW protocol. However, the block mined will contain only the header and the miner’s reward address, instead of transactions. At this point, it switches to PoS protocol. A random group of validators is chosen to sign the new block. Similar to PoS protocol, a validator who has more currency in the network, has a better probability of getting to sign the block.
The reward or fees is split between the miners and validator who signed the block.
Proof of Burn (PoB)
Proof of Burn is similar to virtual PoW. Unlike PoW, where we burn a lot of resources like power, in PoB we do not burn resources directly. Instead we burn coins. This can mean either cryptocurrency or even native currency.
In PoB, coins are burnt by sending them to un-spendable address. PoB works by burning coins received through PoW process.
Proof of Capacity (PoC)
As the name suggests, Proof of Capacity employs an algorithm where the miner who offers more hard disk space to the network to store data gets a better chance at mining blocks.
Variations of this include Proof of Storage and Proof of Space protocols.
Proof of Elapsed Time (PoET)
This is a consensus protocol by Intel. The idea is that every participant has to wait a random amount of time. The participant that finishes first becomes the leader of the new block.
This is done through a trusted execution environment or TEE (such as SGX).
There are a couple of other consensus protocols like Proof of Importance, Proof of Delegated Stake, Proof of Identity.