Proof of History (PoH) is a technology intended to solve the problem of time on blockchain. Most blockchain networks refer to a centralized source of time to give the network a median timestamp, which is used to validate transactions in the order they are received. PoH offers "timestamps" to be built into the blockchain itself, and is done through a verifiable delay function. This is essentially a cryptographic clock, which is intended to allow people running nodes to know what time a transaction is submitted and thereby achieve high transactions per second. Proof of History has been combined with Proof of Work to develop a hybrid consensus mechanism for blockchain networks.