What is a Hashgraph, & how is it different from a blockchain?
Tags: hashgraph, hederahashgraph, blockchain, javascript
Published: 2021-04-20 03:22:49

What is a Hashgraph?
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**Hashgraph** is a Proof of stake distributed ledger technology and governing body built from the ground-up to support new and existing applications running at web scale. 

It is also a data structure which resembles a directed acrylic graph, based on two unique techniques, i.e., Virtual Voting and Gossip about Gossip. Hashgraph uses HBAR as its native cryptocurrency of the Hedera public network. 

What does Hbar Crypto do? 
Hbars are used to power decentralized applications and protect the network from malicious actors. Developers use hbars to pay for network services, such as transferring hbars, managing fungible and non-fungible tokens, and logging data. 

**What is Gossip about Gossip?**
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Gossip about Gossip means to spread a piece of information to another person who is not aware of it yet. It can be like a protocol to send information between nodes in a network. The nodes send data to random members in the network with the history of the previous transaction; this results in the circulation of all the information among all the members at a very fast speed.

**What is Virtual Voting?**
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Virtual voting is a type of consensus algorithm defined as the way a node gets to know whether the transaction is valid or not. If any transaction has 2/3rd of the node as a witness in the network, then it is a valid transaction. No matter if a third node turns Byzantine, the algorithm would still perform its function because Hashgraph is based on Byzantine Fault Tolerant System. The voting takes place over plenty of rounds.

**How is Hashgraph different from a blockchain?**
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 1. **Open-source vs. Patented** - Blockchain technologies like bitcoin are open-source; its design is public, nobody owns or controls Bitcoin and everyone can take part of it. Hedera Hashgraph holds a patent over its unique consensus algorithm, but its services, mirror nodes, and various tools were all released as Open Source while the platform is released as Open Review.

2. **Forkable vs unforkable DLT**- Blockchain being open sourced does allow for disputes to result in forking creating instability and uncertainty for those building on top of it. Hedera Hashgraph releases its code for review so that the community can understand what the code does, to build trust, and to allow suggestions for changes to the code. But it is limited to open review so that it will not be used to create a fork or split of the network. As a way of ensuring the ledger will be stable, without forking or splitting.

3. **Different way of coming to consensus** - Blockchain based DLTs have numerous types of consensus algorithm. All with different pros and cons, suited for different use cases. Its most popular being **proof of work** used by Bitcoin. Hedera Hashgraph uses a "virtual voting" consensus algorithm that sidesteps most of the Proof of work problems and bottlenecks, allowing it to provide low-cost and high performance without failure. Without the need for high computation power and electrical supply. 

4. **Mined coins vs minted coins** - Mining is the process of creating a new block with hashes and adding it to the blockchain. Generating just any hash for a set of bitcoin transactions would be trivial for any modern computer, so to turn the process into "**work**," the bitcoin network sets a certain level of "*difficulty*." This is what I understand as mining. A puzzle where a group of computers guess at a number until one guesses right. The one that guesses right gets to add a block to the blockchain and is rewarded with a Bitcoin. This hapends every 10 minutes on average. It makes the puzzle gradually harder and halves the reward every 4 years for reasons*. This seemed ok at first but as it turns out this makes the bitcoin network not scale at the level needed to replace visa as the network gradually gets slower & more expensive intentional to avoid forks and other reasons*. For more info on the bitcoin scaling problem look [here][1] Hashgraph sidesteps that scaling problem by removing mining entirely and using an entirely new ledger structure, the Hashgraph. That's why all the Hbar are already made. They are locked up and are to be gradually released for reasons*. But Hashgraph is still trying to become a decentralized network, and requires computers for it to validate transactions. Even thought Hashgraph native coin (Hbar) can't be mined since all coins were minted from day one, there is still an incentive to pony up your computer and electricity. You can't mine more Hbar, but soon you can set up a node and get transaction fees for it. Or you can own Hbar and lend them to nodes and get a transaction fee for that.

5. **Cryptographic hash security vs aBFT** - A cryptographic hash function has provable security against collision attacks if finding collisions is provably polynomial-time reducible from problem P which is supposed to be unsolvable in polynomial time. The function is then called provably secure, or just provable. While a Hashgraph is asynchronous Byzantine Fault Tolerance (aBFT) - the highest degree of security a consensus algorithm can provide. ABFT means that finality of consensus will be reached with 100% probability if a) attackers control less than 1/3 of the voting power over consensus and b) we assume only that messages from an honest node will eventually get through, but make no assumptions about how long it will take to do so. Specifically, the attacker must control less than 1/3 of the stake in a proof-of-stake system, or less than 1/3 of the nodes in a system without proof-of-stake. The attacker can control the entire communication network in the sense that the attacker can delete messages, or delay messages for arbitrary amounts of time, with the only limitation being that if honest node Alice repeatedly tries to send messages to honest node Bob, eventually one will get through. The system is resilient to attacks on both network nodes and the communication network itself, as long as both types of attacks are within the limits above. The finality of consensus can be contrasted with the probabilistic confidence of proof-of-work systems, where there is always a chance (even if small) of a transaction being retroactively rolled back.

6. **Centralized vs decentralized from the get go** - Hedera Hashgraph aims to be fully decentralized, but it's not that easy to get right. You see Bitcoin and Ethereum started out decentralized from the very beginning anyone could join and contribute to the network with mining, but with time a concentration of pools emerged where electricity was cheap and whales that got in early made up far too much of the majority making the network more and more centralized exposing it to attacks and giving those people leverage over the network. Hashgraph wanted to avoid this very outcome. They are trying a different approach where they will start centralized and slowly be opening it up to the public becoming more decentralized over time.

#19: Path to a Trusted, Empowered Digital Future with Co-founders Dr. Leemon Baird & Mance Harmon : https://hedera.com/podcast