Consensus Blockchain Primitive
Proof of History
Cryptographic clock providing verifiable passage of time
What is Proof of History?
Proof of History (PoH) is a consensus mechanism component created by Solana that provides a cryptographic timestamp for events. It creates a historical record proving that events occurred at specific moments in time.
How It Works
SHA-256 Hash Chain
- Each hash uses previous hash as input
- Creates verifiable sequence of hashes
- Acts as a cryptographic clock
- Parallel verification possible
Integration with PoS
PoH works alongside Proof of Stake:
- PoH provides ordering and timestamps
- PoS provides finality and security
- Validators rotate as “leader”
- Leader produces blocks using PoH
Benefits
No Waiting for Consensus
Nodes don’t need to communicate for ordering:
- Transactions timestamped immediately
- Parallel transaction processing
- Sub-second finality possible
High Throughput
- 400ms block times
- Thousands of TPS
- Efficient validator coordination
Technical Details
hash(data) → hash1
hash(hash1) → hash2
hash(hash2) → hash3
...Each iteration represents passage of time that can be verified.
Trade-offs
- Requires high-performance hardware
- Centralization concerns with validator requirements
- Novel approach with less battle-testing
Where It’s Used
Primarily implemented by Solana, though the concept influences other high-performance chains seeking to solve the ordering problem efficiently.