Proof of Stake Anonymous (PoSA)
First introduced by Cloakcoin , transactions are cloaked by other users who receive a reward for aiding in the anonymization of the transaction. Other users provide inputs and outputs to the transaction and make it impossible to determine the source and destination of the transaction.
Delegated Proof of Stake (DPoS)
Delegated Proof of Stake was first seen on Bitshares blockchain. The way it works is it has users vote for "delegates" who are then given the power to earn profit from running a full node. This method is supposed to be more efficient and protect users from unwanted regulatory interference.
Proof of Importance (POI)
An expansion by NEM called Proof of Importance was introduced to promote economic activity. Each account is assigned an importance score that proxies its aggregate importance to the economy. This method helps make sure that all the computers on the network agree with each other and can stop people from spending coins they do not have. Users who are "important" can "harvest" and earn rewards.
Proof of Storage
Proof of Storage was first formulated in 2013. Coins like Storj use Proof of Storage. Instead of using a blockchain, the network uses a blocktree. Also instead of seeing every single transaction listed, the user will only see transactions that are relevant to them. Each node on the blocktree contains a blockchain. As of right now there is no known practical publicly verifiable proof of storage, and no known scheme for independently verifying that a privately verifiable audit was issued or answered as claimed.
Proof of Activity
Proof of Activity (POA) was first proposed in 2012 as an alternative to Proof of Stake. It is a method that compliments Proof of Work and helps prevent a 51% Attack, which is when a user or pool controls 51% or more of a network's mining hashrate. Proof of Activity, in short, selects a random peer from the network to sign a new block. This method requires continuous data exchange. In order to reduce traffic, the block "template" does not include the transaction list and is instead added by the last signer.
Proof of Burn (PoB)
Proof of Burn is exactly what it is called. You are providing proof that you have burned some of your coins in the process of sending a transaction to an address that is unspendable. This method only works with coins mined from Proof of Work crypto currencies. Users will try to burn the most amount of coins to hopefully "win" the block reward. Most times Proof of Burn has been introduced to seed other coins by destroying the value of one.
Proof of Capacity (PoC)
Crypto currencies that utilize Proof of Capacity, also known as Proof of Space, use Hard Drive Mining to validate new blocks. Burst coin was the first to introduce this concept. Proof of Work miners burn resources whereas Proof of Capacity allows you to use allotted space on your hard drive to mine. An algorithm is used to create chunks of data called plots by repeatedly hashing public keys. The more space that you have, the more likely you are to mine a block.
Proof of Checkpoint (PoC)
Proof of Checkpoint is a hybrid system that utilizes any Proof of Stake system with a Proof of Work system. The idea of this concept is to mitigate attacks on the Proof of Stake system; however, it is still subject to an attack on a node that has been offline for an extended period of time and can in turn be used to provide false information about the blockchain.
Every X amount of blocks on the Proof of Stake system requires a Proof of Work block to be mined. Each Proof of Work block contains no transactions and are directly linked to both the Proof of Work network and the Proof of Stake network.
