After the release of Bitcoin, alternatives to its PoW mining mechanism were researched, and PoS was studied in the context of cryptocurrencies.
In 2014, Signum (formerly Burstcoin) became the first practical implementation of a PoS (initially as proof of capacity) blockchain technology[5] and is still actively developed.
For practicality, the verification process needs to be efficient, namely, consume a small amount of space and time.
[citation needed] A proof of capacity is a system where miners are allowed to pre-calculate ("plot") PoW functions and store them onto the HDD.
In this algorithm, miners add a conditional component to the proof by ensuring that their plot file contains specific data related to the previous block.
It is related to a proof-of-storage (but without necessarily storing any useful data), although the Moran-Orlov construction also allows a tradeoff between space and time.
Unlike PoW, where the miners keep changing the block header and hash to find the solution, proof of capacity (as implemented by Burstcoin, and developed further by Signum) generates random solutions, also called plots, using the Shabal cryptographic algorithm in advance and stores it on hard drives.
The spacetime model of Chia also depends on "plotting" (generation of proof-of-space files) to the storage medium to solve a puzzle.