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Hashgraph is a distributed ledger, with guaranteed asynchronous byzantine fault tolerance (aBFT) where consensus is reached with a probability of one. It relies on directed acyclic graph and utilises virtual voting and the gossip protocol. Hasgraph, unlike blockchain based DLTs, has high throughput of tens of thousands of transactions per second, has a mathematically proven fairness thanks to consensus timestamping, and has asynchronous byzantine fault tolerance. Thanks to those properties hashgraph can be employed in decentralised systems which require high performance and security such as auctions, online games and micro-payments.
Hashgraph was patented in the USA by Dr. Leemon C. Baird. First commercial hashgraph ledger was deployed by Swirlds Inc of which Dr. Leemon is co-founder & CTO.
The Hedera Hashgraph platform is currently in development, and is designed to be a new form of distributable consensus. Hashgraph refers to a distributed consensus algorithm, and Hedera is the distributed ledger that will implement the Hashgraph technology. It is a distributed ledger platform similar to Ethereum, that can run dApps and support smart contracts.
The hashgraph technological idea is very similar to blockchain. However, some changes in the process of the transaction validation and consensus achievement approach make hashgraph very different from the traditional blockchain structure.
First of all, hashgraph doesn’t use proof-of-work to validate transactions. There are no difficult computations necessary to maintain the hashgraph-based network which makes it very approachable for the individual users as well as organizations.
The second important improvement of hashgraph vs blockchain is an upgrade of the “block” concept of blockchain. Block is a validated data storage that contains information about transactions and, sometimes, some additional info within a blockchain-based network. The information, contained by the traditional block is mostly a list of the transactions made in a given period of time, a timestamp, the hash of the block and the hash of the previous block. The inclusion of the second hash is what makes blockchain an actual chain of blocks. Hashgraph use an “event” concept as an alternative to block. Event is similar to a block, it also contains a timestamp and a list of transactions, but instead of block hashes it includes two regular parent hashes. As a result, while blockchain is building something like a straight line by choosing a particular node that will be a platform for adding the new blocks, hashgraph is establishing a network of nodes that are all valid and interconnected within multiple lines of the nodes.
So, because blockchain is inevitably building “dead” branches around the main chain, it requires the regular pruning of the network in order not to let it grow out of control. Unlike blockchain, hashgraph develops a network of branches, that are connected by the interactions between the events within them. Hashgraph algorithm provides near-perfect efficiency in bandwidth usage, handling hundreds of thousands of transactions per second and verifying over one million signatures per second. Time to finality is measured in seconds; not minutes, hours, or days. Consensus is 100% certain and, unique to Hedera, guaranteed to never change.”
Recalling in a random mode, all participants in Hashgraph creating operations (aka transactions), which should be confirmed by several other participants without the need to include the entire network in the process. Visually, it looks pretty nice and somehow resembles Japanese Bonsai plants. Those who want to delve into the understanding of this algorithm, we recommend to visit the official site and get acquainted with a very compact graphical explanation of the principle of Hashgraph.
The speed of applications based on the consensus of Hashgraph allows you to record events in a distributed registry almost in real time. This means that you can build fast and secure (serverless functionality, resistance to DDOS attacks, hacking, zero hosting) of the Internet ecosystem of things and working environment space. According to Swirlds, even distributed work with text documents becomes possible.
Diagram of hashgraph data flow consists of circles and lines. On the graph each node has its own vertex. The circle represents an event when one of the network nodes exchanges information with another node. Whenever such communication occurs, each of two nodes marks the event on their vertex and links the event with the preceding event on their vertex. Thus the full graph is simply a representation of a history of how the network nodes talked to each other. This is known as the gossip protocol.
Gossip protocol (sometimes also referred to as “epidemic protocol”) is a computer to computer communication procedure that is based on the process of information spreading in social networks or the epidemics transmission. Gossip protocol is not unique feature of the hashgraph technology. It is implemented in blockchain for maintaining distributed database consistency by making nodes send information about newly received transactions to the neighbouring nodes and then making neighbouring nodes send information about getting information about the initial transaction. In the whitepaper “The Swirlds hashgraph consensus algorithm: fair, fast, byzantine fault tolerance” this process is called gossip about gossip. It is used in hashgraph to establish a guaranteed path for transaction information spread. It means, that if several malicious nodes try to block transaction information from being shared between the nodes in the network, gossip protocol will ensure a randomized selection of nodes that will get the info and spread it further.
Thanks to the timestamping, hashing and digital signatures usage for communication events, it is possible the for network nodes to reconstruct whole hashgraph locally. The protocol guarantees that at the certain point node knows that sufficient number of other nodes also reconstructed hashgraph. The node uses local copy of hashgraph to compute what voting decision it should make when the consensus is decided. Thanks to that, there is no need for the nodes to exchange any additional information to reach consensus. The node can simply say that other nodes which have the same hashgraph will vote in the same manner as they compute their decisions from the identical set of data. This is known as virtual voting as votes instead of being casted are computed.
Hashgraph is said to have asynchronous byzantine fault tolerance if less then 1/3 nodes on the ledger can be attackers who can collude and delay or delete messages between any two nodes. However it is assumed that if honest member repeatedly sends messages to another member, one message will eventually get through.
As a file storage, Hedera hashgraph implements Merkle Trees and Merke DAGs (Directed Acyclic Graphs) meaning that if two files have some bytes in common, the network might only store one copy of the common bytes. However, those files can be manipulated with Java classes by the developers to build decentralized applications in the network.
Hashgraph validation technology
The breakthrough of the Hedera hashgraph is in its validation technique. Its validation process is what makes hashgraph so fast and energy efficient. It is also a main technology behind its consensus.
Hedera - the distributed ledger of the hashgraph network is divided in rounds. The round is created when one event becomes able to connect more than 2/3 of the events of the current round by more paths than 2/3 of the node population. It is done to ensure that vertices (events) of hashgraph are “strongly seeing” another vertices. Events are strongly seeing each other if they are connected by the multiple directed paths passing through enough members. The “enough” is established by the network. That concept is the foundation for the rest of the mathematical proof of Byzantine agreement with probability one. Byzantine agreement establishes a network’s Byzantine fault tolerance. Byzantine fault tolerance means that no single member (even participating in groups) can prevent the community from reaching a consensus or to lose it after reaching.
After the new round is created the first new nodes of the the second round will vote if they agreed upon the data contained in the first row of events of the preceding round. This voting is basically a process of the verification of being connected to these nodes.
The last stage of validation is the collection of the 3rd round nodes answers. To collect the data the 4th round nodes are required. According to the round creation rules they need to strongly see the 3rd round node. When one of the 4th round nodes succeed to collect more than 2/3 of the population of positive votes upon the data in the 2nd round then the consensus is found and the data is validated.
Hashgraph vs blockchain
Hashgraph, similarly to the bitcoin blockchain is a decentralized online transaction record that can be accessed by several parties and other users.
Both systems have decentralized data storage, both use hashing, encrypted signatures etc.
The creators of the hashgraph focusing on the speed of transactions, which is 50,000 times higher than that of the blockchain: 250,000 transactions per second.
Hashgraph is more defended against users manipulations. With the increased complexity of calculating code, it is less likely to find it from a single mining person. Search requires a lot of energy. In the future, success will be on the side of large conglomerates of miners. They already manipulated the network, after which the pool was disbanded. But theoretically, the threat remained.
The blockchain is started to be a lottery where everyone is fighting for build the main "tree trunk", all branches in the Hashgraph get the right to live and development, moving in parallel. It means that any of nodes which use in process of transaction can’t stop the whole process.
Hedera Hashgraph ICO
Hedera has a performed round of ICO. It happened from August 14 to August 16 of 2018, had a target fundraising of $120 000 000 and was only for accredited investors.
The team only managed to gather $100 000 000, however, the ICO may be considered successful.
Now developers don’t give any news about presale of hashgraph coins, when it starts or when it will end.
Hashgraph white paper could be looked, saved and downloaded on official site.
Full information about the Hedera Hashgraph ICO review
Advantages and disadvantages of Hashgraph
- Hashgraph is much faster in terms of networks transaction speed and is potentially better scaled. Proof-of-work blockchains are limited in this terms due to their consensus algorithms. The hashgraph is only limited by the bandwidth of the internet and can perform up to 250 000 transactions per second.
- The hashgraph network is more secure and robust than proof-of-work blockchain. Hashgraph distributed consensus technology is A-BFT (Asynchronous Byzantine Fault Tolerant), which means that while less than 1/3 of the nodes are malicious the protocole will always find the right consensus.
- In contrast to blockchain networks, hashgraph doesn’t allow transaction blockage or delay. While blockchain proof-of-work allows miners to choose on which transaction to validate (based on its fees, users, etc.), the hashgraph technology’s timestamp protocol is absolutely fair to every user.
- The hashgraph public implementation is yet to be issued. Despite its efficiency being mathematically proved, real-life usage can show different results. Even the fastest network can fail to fulfill the expectations in the actual usage.
- While blockchain is protected from various attacks by the immense amount of electric power and computing resources needed to make changes in the network, hashgraph has no such protection. It is true that it is theoretically protected from malicious intentions by consensus but no one can say for sure that there will be no way found to bypass it when the network becomes public.
- The design of hashgraph doesn’t allow forks which may become a very significant obstacle in case of the existence of unidentified vulnerabilities and mistakes in architecture that will be missed in testing and while the network is young.
Hedera Hashgraph Cryptocurrency
The Hedera hashgraph network will have a native cryptocurrency, which is a utility token that grants token holders access to distributed applications on the platform. The team expects the token to act as a unit of value to motivate responsible use and governance of the platform. The advantages of speed and efficiency of the hashgraph-based network can provide its cryptocurrency with such features as:
- High accessibility
- Democratic virtual voting
- Low transaction fees
- Convenient and practical everyday payments
- Secure network
- Reasonable energy consumption
The ultimate goal will be to establish a cryptocurrency platform that supports smart contracts, dapps development, large number of interested application developers with an implementation of all the features of the hashgraph technology.
- Hedera platform: Cryptocurrency
- Hedera platform: Token
- Medium.com - Tim Rb: Hashgraph for dummies
- ICODROPS: Hashgraph ICO
- Leemon Baird, Mance Harmon, and Paul Madsen: Hedera: A Governing Council & Public Hashgraph Network
- Hedera Hashgraph website
- Wikipedia: Quantum Byzantine agreement
- Leemon Baird: HASHGRAPH CONSENSUS: DETAILED EXAMPLES