Proof-of Space-time (PoSt), as it is commonly used in relation to Filecoin, is a method by which a storage miner proves that they are still storing a unique piece of data for the network. PoST means that anyone can now guarantee that they are using a specific amount of space on their storage.

PoSt is similar to proof-of-capacity in several ways: both require network participants to have a financial incentive to participate honestly in the network and have no benefit from harming the network. PoSt, on the other hand, distinguishes itself by allowing network participants to demonstrate that they have been physically storing data for a specified period of time. This is demonstrated by randomly selecting miners and reading their data for verifications.

The creators of proof-of-spacetime, Tal Moran and Ilan Orlov, refer to this as the "Rational' Proofs of Space-Time because the true cost of storage is proportional to the product of storage capacity and time that it is used.

Chia Using Proof of Space-time work

In the Consensus Protocol, Chia is using the first new Nakamoto consensus algorithm since Bitcoin. Called Proof of Space and Time, Bram Cohen created Proof of Space and Time. Chia’s new innovative Nakamoto consensus algorithm removes the energy demands of Proof of Work from the system, making it as energy efficient as possible.

Proof of space can be demonstrated if you have some disk space on your hard disk drive (HDDs) or solid-state drives (SSD) that are not being used. Chia blockchain users will "seed" unused space on their hard disk drive (HDDs) or solid-state drivess (SSD) by installing software that stores a collection of cryptographic numbers on the disk in the form of "plots."

These individuals are referred to as "farmers." When the blockchain broadcasts the next block's challenge, farmers can scan their plots to see if they have the hash that is closest to the challenge. The probability of a farmer winning a block is determined by the percentage of total space that a farmer has in comparison to the entire network.

While on the other hand, Proof of time necessitates a brief interval of time between blocks. Proof of time is implemented using a Verifiable Delay Function, which takes an amount of time to compute but is very fast to verify. The key concept of a VDF is that they require sequential computation and because having many parallel machines provides no benefit, electricity waste is minimized. There will most likely be a small number of VDF servers (“Timelords”), as the fastest one will always finish first, and it only takes one fast and fair Timelord on the network to complete a block and advance the chain.

You can read the Chia Network's Green Paper for a more in-depth understanding and details on how Proof of Space and Time for Nakamoto consensus works.

The Importance of Consensus Protocols

Consensus protocols serve as the foundation of blockchain by assisting all nodes in the network in verifying transactions. The consensus protocol ensures that every new block added to the Blockchain is the one and the only version that matches all nodes in the Blockchain agree on.

Bitcoin's consensus protocol is proof of work (PoW), which is both energy and time-consuming. In comparison to Visa and MasterCard, the rate of transaction verification in Bitcoin is relatively slow. As a result, consensus protocols have been created.

Other Consensus Protocols

Proof of Stake (PoS)

A validator is chosen and assigned a block as proof of stake consensus. To begin validating, the miner must allocate a portion of his cryptocurrency. If the miner is successful in invalidating the transaction, the award is the stake they initially pledged, plus certain transaction fees. This is a method of penalizing bad behavior while incentivizing good behavior.

Proof of Work (PoW)

One of the first consensus protocols used in blockchain applications as proof of work. It works by computing hash values and validating transactions until a certain number of trailing zeros are discovered in the hash value. A nonce is defined as the number that generates the hash with the specified number of trailing zeros. A nonce is a random number generated by the hash function that generates the specified number of trailing zeros.

Proof of Storage (PoS)

Similar to a proof-of-space, but instead of demonstrating that space is available for solving a puzzle, the prover demonstrates that space is being used correctly to store a piece of data at the time of proof.