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I have some basic doubts about consensus algorithm like hashgraph. For instance, let's take Raft the simplest leader based consensus algorithm, we cannot use it in a decentralised setting because it's very easy for a single attacker to take control of the cluster by spinning thousands of nodes to support him.

"In summary, the voting based algorithm makes it very easy for the attacker whether its leader based or leaderless. So we cannot use it in a decentralised setting."

Algos like PoW make its difficult for a single attacker to take over the network through the computational puzzle.

Taking about hashgraph it's again a voting based algorithm, so wondering how it prevents a single attacker from getting control of the network in a decentralised setting (where you cannot trust your peers)???

I do understand how hashgraph works but wasn't able to visualise it in a decentralised setting. Any insights? Thanks

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  • Why tagged as Bitcoin core? – marshal craft May 11 '18 at 11:56
  • yeah thats a mistake, removed it – Minisha May 11 '18 at 13:53
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Seeing this a year late, but if this is still a question then -

Hashgraph isn't exactly a voting based algorithm. It does "virtual voting" through "gossip about gossip" i.e. nodes not just gossip that there is a new transaction, but also gossip about when they heard it, who told them/how they heard it (literally gossiping about the gossip!) This way every node has the COMPLETE knowledge of the network. If node A knows everything that node B knows, A can also find out what B will vote (WITHOUT B actually voting!)

Also, hashgraph never says that 51% attack can't occur. Through Byzantine Fault Tolerance even a 34% attack can occur (if more than 1/3rd of the nodes are malicious). Hashgraph just says that DDoS or DoS (Denial of Service) attacks can't occur because there are no leaders.

Refer to the Hashgraph whitepaper or the scientific paper on its consensus algorithm: https://docs.hedera.com/docs/hashgraph-overview or https://www.hedera.com/whitepaper

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