Proof of Spacetime
In short: Proof of Spacetime (PoSt) is a way for a network participant to prove that they have dedicated a certain amount of storage space to the network over a…
Proof of Spacetime (PoSt) is a way for a network participant to prove that they have dedicated a certain amount of storage space to the network over a period of time. Simply put, it shows that data is still being stored, not just that it was stored once.
Why it matters
Decentralized storage networks pay providers to keep other people's files, so they need a way to check that the data is really kept without downloading it all. With PoSt, providers answer regular challenges with small cryptographic proofs, and those who fail can lose rewards or collateral. Filecoin is a well-known network that uses Proof of Spacetime. Like Proof of Work and Proof of Stake, it ties rewards to a scarce resource, here disk space over time.
Example
A storage provider agrees to keep a client's file for an agreed period. At regular intervals, the network issues a random challenge about specific parts of the stored data. The provider computes a short proof from the data it holds and submits it on chain. As long as valid proofs keep arriving on time, the provider earns rewards; if they stop, the network treats the storage as lost.