Clear DefinitionsProof-of-History
1 min read
Pronunciation
[proof-uhv-his-tuh-ree]
Analogy
Think of Proof-of-History as a tamper‑proof diary: each new entry includes a hash of the previous entry, so anyone can verify when entries were made and in what order.
Definition
A cryptographic clock that encodes time passage into a verifiable sequence of hashes, enabling nodes to agree on event ordering without messaging overhead.
Key Points Intro
Proof-of-History provides ordering guarantees via:
Key Points
Sequential hashing: Each output becomes the next input in a continuous hash chain.
Timestamping: Hash chain indices serve as cryptographic timestamps.
Low communication: Nodes verify order without exchanging clocks.
Integration with PoS: Often combined with Proof-of-Stake for leader election.
Example
Technical Deep Dive
A Verifiable Delay Function (VDF) based on repeated SHA‑256 hashing produces a single chain: H₀ = seed; Hₙ = SHA256(Hₙ₋₁). Each hash output includes the count n, enabling fast verification by recomputing a small number of steps. Nodes embed these hashes in block headers, providing a global ordering prior to PoS confirmation.
Security Warning
Relying on local clock drift can desynchronize hash chain indices; ensure all validators start from the same genesis seed.
Caveat
PoH itself does not finalize blocks; an additional consensus layer is required to prevent forks.
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