Proof of History

Proof of history, or PoH, is a technique for proving that time has passed between events by running a continuous sequential hash function whose output cannot be computed in parallel or skipped ahead. A block producer stamps transactions into this verifiable ordering, so other nodes can confirm the sequence afterwards without exchanging messages to agree on timestamps. Solana is the network best known for using it. Importantly, proof of history is not a standalone consensus mechanism: it acts as a cryptographic clock alongside proof of stake, which still decides who produces blocks and which chain is canonical. The purpose is throughput — cutting the communication normally needed for nodes to agree on transaction order.