How PBFT algorithm works

Question

I am confused with the working of practical byzantine fault tolerance (PBFT). How does it work in Hyperledger fabric??

Can someone please explain me the concept??? Please share papers if there is any

Answer 1

PBFT is a way for a distributed network to reach the consensus set for the Blockchain even if some nodes are malicious. In Hyperledger, for a transaction to be approved, a certain number of nodes must agree to this. PBFT is the feature of the application to approve the transactions even if some nodes are not approving the transaction.

When a Hyperledger transaction is made, the transaction details are sent to the nodes in the network. There are might some nodes that will approve the transactions and some nodes that won't. The majority (or a minimum specific number) of nodes have to approve the transaction for the transaction to be completed.

Comments

Hey @Kiran. Thanks for explaining about PBFT but I am not understanding how it helps in Hyperledger.

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In a Hyperledger network, there might be some nodes(malicious nodes) that will on purpose without a valid reason reject the transaction. If this is allowed, then the integrity of Blockchain will be affected. To avoid this PBFT is used.

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Hi @Esha. When you use PBFT, the vote/decision of the malicious nodes to approve/reject the transaction is diluted. Think of the situation where the protocol is such that 100% of the network should make the same decision for the transaction to be successful. In this case, if there is a malicious node in the network, that node might reject a valid transaction. And because 100% of the network should agree to approve the transaction and one node is rejecting the transaction, a valid transaction will be unsuccessful. To avoid this, PBFT is used where 100% of the vote to do something is not required.

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Okay, got it. But if 100% is not required, then how much percent is required?

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@Esha, this depends on the implementation. The most used practice is that 51% of the network should agree on the decision. But if you have more/less trusted nodes, you can increase the percentage.

Answer 2

Hyperledger 0.6 is depricated for quite some time now. They are now upgrading the version to hyperledgr v1.1. There are lot of protocol changes that have happened in the verion change. But they have preserved the archived repository and the protocol specification. Also, the explanation of PBFT is a long description, here is the paper you can refer

Answer 3

Everything you need to know:

https://blockonomi.com/practical-byzantine-fault-tolerance/

Answer 4

PBFT stands for Practical Byzantine Fault Tolerance which is derived from Byzantine General's problem. According to PBFT, some amount of fault (different/wrong decision) can be tolerated without affecting the integrity of the network. PBFT is used in Hyperledger in the transaction approval process to avoid malicious decisiosn