PBFT algorithm in hyperledger

Question

Can anyone explain PBFT Algorithm in detail without giving any link for the same? And how it works in hyperledger. So, once the transaction is sent to

Answer 1

In Corda, consensus is provided by notaries. It is up to the notary operator which consensus algorithm they use. BFT is one option. You can see a Corda BFT notary sample here: https://github.com/corda/corda/tree/master/samples/notary-demo.

To answer your questions:

(1). Who validates the transaction?

The transaction is validated by a cluster of one or more notaries. Notaries are nodes with the sole purpose of deconflicting double-spend attempts.

(2). How the consensus is achieved on the transaction?

Using a standard BFT algorithm. Each node in the notary cluster votes on whether they consider the transaction to be a double-spend attempt. The final decision is based on a majority rule, and can tolerate up to 1/3rd of the nodes in the cluster being malicious.

(3). How the transaction is committed to the blockchain?

In Corda, there is no central store of information that the transaction is committed to. The notary cluster simply adds the spent state reference to an internal database table. It will check future attempts to spend states against this table, and reject the spending attempt if the state reference is already stored there.