What is Hashgraph?

Hashgraph is a consensus algorithm based on a virtual voting protocol combined with gossip about gossip, developed by Leemon Baird. Instead of constructing a blockchain, Hashgraph builds a directed acyclic graph of events through a gossip protocol — each node randomly selects another node and shares all events it knows about. Each event records which events the creating node knew about at the time (the gossip history), which provides enough information for every node to independently determine what every other node knows. This allows nodes to calculate the results of a virtual election without actually sending any vote messages — they can mathematically determine how each node would have voted based on the gossip history recorded in the hashgraph structure.

Hashgraph achieves asynchronous Byzantine Fault Tolerance (aBFT), which is the strongest level of BFT — it guarantees consensus will be reached even if messages are delayed by arbitrary amounts, as long as they are eventually delivered. The protocol provides fairness guarantees including consensus time-stamping (transactions are ordered by the median of the times each node first received them) and fair access (no single node can significantly delay a transaction's inclusion). Finality is achieved in seconds, and the protocol can process thousands of transactions per second. Hashgraph's mathematical proofs of aBFT safety and liveness set it apart from protocols that rely on timeouts or synchrony assumptions. The virtual voting mechanism eliminates the overhead of actual vote messages, making it highly communication-efficient.

Hashgraph powers the Hedera network, which launched its mainnet in September 2019. Hedera is governed by a council of up to 39 organizations including Google, IBM, Boeing, and other major enterprises. The Hashgraph algorithm is patented by Swirlds (the company co-founded by Leemon Baird), with the Hedera network being the only authorized public ledger using it. Hedera offers services including cryptocurrency transfers (HBAR), smart contracts (EVM-compatible), token creation, and a consensus service for verifiable timestamps. The network has been adopted for various enterprise use cases including supply chain tracking and carbon credit markets.