Proof of History (POH): A major problem in distributed systems is to maintain a notion of time, nodes have to:
1) trust some external entity to give the correct time(not trustless).
2) wait for the majority of honest nodes to sign on a message. (Costly).
Now, nodes can easily verify the order of messages they received by looking at the VDF encoded in the messages without trusting any external entity or waiting for majority signatures.
This makes the Solana blockchain fast.
Proof of History (POH): A major problem in distributed systems is to maintain a notion of time, nodes have to:
1) trust some external entity to give the correct time(not trustless).
2) wait for the majority of honest nodes to sign on a message. (Costly).
Solana solves this by encoding a special timestamp in its message.
The special timestamp is called PoH which is a VDF(Verifiable Delay function)
A VDF requires a particular number of successive steps to get an output, yet it produces a publicly verifiable outcome at every step.