# What is Proof-of-History (PoH)?

One of the most important challenges for distributed networks, such as blockchains, is time synchronisation. Because time is synchronised in distributed systems, one may encounter various fraudulent activities. It’s possible to determine the exact time of a specific transaction with the Solana blockchain’s Proof-of-History protocol. If you’re wondering what Proof-of-History is, then you will find the answer in this article.

# What is Proof-of-History?

Proof-of-History is a protocol that attempts to prove the order in which transactions took place on the blockchain. From this they can deduce whether the transactions are listed correctly. Proof-of-History is a method used on the Solana network − it keeps the network running fast while also maintaining its security. Transactions on the Solana blockchain are carried out using the SHA256 hash function. The PoH method, alongside the Solana protocol’s other unique features contribute to it being able to handle 50,000 transactions per second (TPS — Transactions per second). Solana’s block times can be as low as 400ms − extremely fast compared to roughly 10 minutes for Bitcoin and 15 seconds for Ethereum.

# How Proof-of-History (PoH) works

The first person verifying the network is assigned the first row and spends 5 seconds finding the next block. The second person verifying the network is assigned the second row and spends 5 seconds finding the next block. There is a 10 second transition in total. The third person verifying the network is assigned the third row and spends 5 seconds to find a block. The process so far has only taken 15 seconds in total. For each block, only 5 seconds are required to complete the transaction. Each validator is positioned one after the other. Once a validator has completed a transaction, other validators must pause for 5 seconds. The process is visible to all users who perform proof-of-history. If there was a fourth validator, they would verify 5 seconds after the third validator.

# Why is Proof-of-History important?

With the Proof-of-History method, delays on the blockchain network are reduced. The blockchain is made more efficient. With the Proof-of-History method, the order of transactions is also fully verified. This eliminates the time that would be spent using another form of verification. Nodes spend less time choosing the order of operations. This means new validators joining the network are selected faster.