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What Is Proof of History?

proof of history explained

In this article, we will explain what Proof of History is, how it works, why it is so fast, and we’re gonna see why delays on the network aren’t an issue.


What is Proof of History?

Proof of History is used to lighten the load of the network nodes in processing blocks by offering a method of encoding time itself into the blockchain.

When we talk about a regular blockchain, reaching consensus regarding the time spent for mining a block is essential, just like reaching a consensus over the existence of the transactions in that block is. Therefore, timestamping is important as it lets the network know that transactions took place in a particular sequence.

Basically, Proof of History allows you to create a historical record that shows that an event took place at a certain moment in time.


How Does Proof of History Work?

In a Proof of Work case, the successful block miner becomes the first to find the correct nonce (short for number used only once, representing a whole number used as an input for the computation function of the current block’s hashrate), which needs a particular amount of computing power in order to perform.

But Proof of History relies on a new cryptographic concept, known as Verifiable Delay Functions (VDF). You can solve a VDF with just one CPU core using an exact set of sequential steps. Since parallel processing isn’t allowed, it becomes easy to determine exactly how long it took for those steps to be applied. Thus, the passage of time is clear.

Since Proof of History basically solved the time challenge, the processing weight of the blockchain has changed, making it faster and lighter.

Solana is the blockchain that popularized this way of working. It also uses Proof of History and a security protocol known as Tower Byzantine Fault Tolerance in order to let participants stake tokens so they can vote on the validity of a Proof of History hash. If a bad actor votes for a fork that doesn’t match the Proof of History records, they will be penalized.

Solana also relies on Proof of Stake in order to establish who is allowed to be a block validator.


How Fast Does It All Happen?

Since there isn’t any dependency on local computer clocks or local timeouts between state transitions beyond the Verifiable Delay Function, the VDF will make sure that each block producer can prove that they’ve waited the needed amount of time, so the network can move forward.

The next producer needs to locally generate a portion of the VDF until the scheduled slot. This means that as soon as nodes are received, the state transition can start right when the message is received. This is because there is now cryptographic proof that the producer followed the protocol delays.

By contrast, while Solana confirms 25 blocks proposed by 25 different validators, other networks could confirm only one. 


Are There Ever Delays?

The message can arrive out of order while the cost of network delays is slowly accommodated following the delivery of many packets. As soon as the Proof of History is being reconstructed, the entire data structure makes sure that the appropriate delays that are between all the block producers are indeed correct.

This translates into the network never actually being delayed, and even with variations caused by block producers, it can keep on producing at lightning-fast speeds. Therefore, Proof of History is a mechanism that allows network speeds that have never been seen before in blockchain technology.



In short, Proof of History lets users create a historical record that works as proof that an event took place at a certain moment in time, making the network faster and lighter.

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