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Hedera Hashgraph, commonly known as Hedera, is a
distributed ledger A distributed ledger (also called a shared ledger or distributed ledger technology or DLT) is a system whereby replicated, shared, and synchronized digital data is geographically spread (distributed) across many sites, countries, or institutions. I ...
which uses a variant of
proof of stake Proof-of-stake (PoS) protocols are a class of consensus mechanisms for blockchains that work by selecting validators in proportion to their quantity of holdings in the associated cryptocurrency. This is done to avoid the computational cost of ...
to reach consensus. The native
cryptocurrency A cryptocurrency (colloquially crypto) is a digital currency designed to work through a computer network that is not reliant on any central authority, such as a government or bank, to uphold or maintain it. Individual coin ownership record ...
of the Hedera Hashgraph system is HBAR.


History

Hashgraph was invented in the mid-2010s by the American
computer scientist A computer scientist is a scientist who specializes in the academic study of computer science. Computer scientists typically work on the theoretical side of computation. Although computer scientists can also focus their work and research on ...
Leemon Baird. Baird is the co-founder and chief technical officer of Swirlds, a company that holds patents covering the hashgraph algorithm. Hashgraph were described as a continuation or successor to the
blockchain The blockchain is a distributed ledger with growing lists of Record (computer science), records (''blocks'') that are securely linked together via Cryptographic hash function, cryptographic hashes. Each block contains a cryptographic hash of th ...
concept, which provides increased speed, fairness, low cost, and security constraints. Based on Hashgraph protocol, Hedera Hashgraph mainnet was launched in 2019. The Hedera white paper co-authored by Baird explained that "at the end of each round, each node calculates the shared state after processing all transactions that were received in that round and before," and it "digitally signs a hash of that shared state, puts it in a transaction, and gossips it out to the community." In 2020,
Google Cloud Google Cloud Platform (GCP) is a suite of cloud computing services offered by Google that provides a series of modular cloud services including computing, data storage, data analytics, and machine learning, alongside a set of management tools ...
joined Hedera Governing Council. A year later,
EFTPOS Electronic funds transfer at point of sale, abbreviated as EFTPOS (), is a type of payment transaction in which electronic funds transfers (EFT) are processed at a point of sale (POS) system or payment terminal usually via payment methods such as ...
joined the governing council. In September 2024 Hedera has transferred all source code of the Hedera Hashgraph to the
Linux Foundation The Linux Foundation (LF) is a non-profit organization established in 2000 to support Linux development and open-source software projects. Background The Linux Foundation started as Open Source Development Labs in 2000 to standardize and prom ...
. The sources are now available as the
open-source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use and view the source code, design documents, or content of the product. The open source model is a decentrali ...
and vendor-neutral project
Hiero Hiero or hieron (; , "holy place" or "sacred place") is an ancient Greek shrine, Ancient Greek temple, temple, or temenos, temple precinct. Hiero may also refer to: People * Hiero I of Syracuse, tyrant of Syracuse, Sicily from 478 to 467 BC * ...
.


Distributed ledger

Hedera Hashgraph is a public distributed ledger based on the Hashgraph algorithm. Hedera Hashgraph is developed by a company of the same name, Hedera, based in
Dallas, Texas Dallas () is a city in the U.S. state of Texas and the most populous city in the Dallas–Fort Worth metroplex, the List of Texas metropolitan areas, most populous metropolitan area in Texas and the Metropolitan statistical area, fourth-most ...
. Hedera was founded by Hashgraph inventor Leemon Baird and his business partner Mance Harmon, and Andrew Masanto, adding significant contribution to the team. Previously, Hedera had an exclusive license to the Hashgraph patents held by their company, Swirlds. The Hedera Governing Council voted to purchase the patent rights to Hashgraph and make the algorithm
open source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use and view the source code, design documents, or content of the product. The open source model is a decentrali ...
under the
Apache License The Apache License is a permissive free software license written by the Apache Software Foundation (ASF). It allows users to use the software for any purpose, to distribute it, to modify it, and to distribute modified versions of the software ...
in 2022. Hedera mainnet is maintained by governing council members which include companies such as
Deutsche Telekom Deutsche Telekom AG (, ; often just Telekom, DTAG or DT; stylised as ·T·) is a partially state-owned German telecommunications company headquartered in Bonn and the largest telecommunications provider in Europe by revenue. It was formed in 199 ...
,
IBM International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is ...
, FIS Global, and
Tata Communications Tata Communications Limited (previously known as Videsh Sanchar Nigam Limited) is an Indian telecommunications company. It was a government-owned telecommunications service provider before being sold to the Tata Group in 2002 under the Third ...
.


Hashgraphs

Unlike blockchains, hashgraphs do not bundle data into blocks or use miners to validate transactions. Instead, hashgraphs use a "gossip about gossip" protocol where the individual nodes on the network "gossip" about transactions to create
directed acyclic graph In mathematics, particularly graph theory, and computer science, a directed acyclic graph (DAG) is a directed graph with no directed cycles. That is, it consists of vertices and edges (also called ''arcs''), with each edge directed from one ...
s that time-sequence transactions. Each "gossip" message contains one or more transactions plus a
timestamp A timestamp is a sequence of characters or encoded information identifying when a certain event occurred, usually giving date and time of day, sometimes accurate to a small fraction of a second. Timestamps do not have to be based on some absolu ...
, a digital signature, and cryptographic hashes of two earlier events. This makes Hashgraph form an asynchronous Byzantine Fault-Tolerant (aBFT)
consensus algorithm A fundamental problem in distributed computing and multi-agent systems is to achieve overall system reliability in the presence of a number of faulty processes. This often requires coordinating processes to reach consensus, or agree on some data va ...
.


Criticism

It has been claimed that hashgraphs are less technically constrained than
blockchain The blockchain is a distributed ledger with growing lists of Record (computer science), records (''blocks'') that are securely linked together via Cryptographic hash function, cryptographic hashes. Each block contains a cryptographic hash of th ...
s proper.
Cornell Cornell University is a private Ivy League research university based in Ithaca, New York, United States. The university was co-founded by American philanthropist Ezra Cornell and historian and educator Andrew Dickson White in 1865. Since ...
Professor
Emin Gün Sirer Emin Gün Sirer is a Turkish-American computer scientist. Sirer developed the Avalanche Consensus protocol underlying the Avalanche blockchain platform, and is currently the CEO and co-founder of Ava Labs. He was an associate professor of com ...
notes that "The correctness of the entire Hashgraph protocol seems to hinge on every participant knowing and agreeing upon ''N'', the total number of participants in the system," which is "a difficult number to determine in an open distributed system." Baird responded that "All of the nodes at a given time know how many nodes there are."


References

{{Cryptocurrencies, state=expanded Distributed computing Cryptography