Hashgraph

Hashgraph is a distributed ledger technology and consensus algorithm developed by Leemon Baird and the company Swirlds. Unlike traditional blockchains, it uses a directed acyclic graph (DAG) to record events. Each node maintains a local copy of the ledger as a series of events; an event contains transactions and references to two parent events: the node’s own previous event and another node’s previous event. Nodes disseminate events through a gossip protocol, where peers randomly exchange information about the latest events.

Consensus is achieved through gossip about gossip and virtual voting. As events propagate, each node can reconstruct a view of the network’s history and determine a total ordering of events without a centralized leader. The protocol is asynchronous Byzantine fault tolerant (aBFT): it tolerates up to less than one-third of faulty or malicious nodes while preserving safety (no conflicting orders) and liveness (progress).

Properties and performance: Hashgraph aims for high throughput and low latency relative to traditional distributed ledgers. Because no single leader dictates the order, the network can progress quickly when participants follow the protocol. The use of consensus timestamps is intended to provide fair ordering of transactions, reducing the ability of submitters to influence the sequence based on timing.

Applications and governance: The most prominent implementation is Hedera Hashgraph, a public network governed by a council that coordinates governance and development. Hedera offers services such as cryptocurrency transfers, smart contracts, file storage, and a consensus service. The Hashgraph algorithm is patented by Swirlds, and licensing arrangements accompany its use in different systems.

Relation to blockchains: Hashgraph is often described as an alternative to blockchains, using a directed acyclic graph rather than a single chain. While sharing goals of fast, secure, and scalable consensus, its design, patenting, and governance have drawn different critiques and levels of public scrutiny compared with open-source blockchain protocols.