goal is to protect against catastrophic system failures by reducing the

influence of these malicious nodes.

To avoid a complete failure, the Byzantine General’s problem stands

for a situation where the involved parties must agree on a single

strategy; however, it assumes that some of the involved parties might

be corrupt or unreliable.

PBFT focuses on providing a practical Byzantine state machine

replication that tolerates Byzantine faults (i.e., malicious nodes) by

assuming that there are independent node failures and manipulated

messages sent through specific nodes.

In a PBFT system, nodes are sequentially ordered, with one node

being the leader and others referred to as the backup nodes. All nodes

in the system communicate with one another, and the goal is that all

honest nodes will come to an agreement on the state of the system

using a maj ority rule.

Between the nodes, the two functions of communication are: the

message that came from a specific peer node must be proven by the

nodes, and they must also verify that the message was not modified

during transmission.

The number of malicious nodes must not equal or exceed one-third of

all nodes in the system in a given vulnerability window for the PBFT

system to function. Similar to the proof of work consensus

mechanism, the more nodes there are in a PBFT network, the more

secure it becomes.

The four phases in which the PBFT consensus rounds called views are

broken are as follows:

1. A client sends a request to the leader node to invoke a service

operation.

2. The leading node broadcasts the request to the backup nodes.

3 . U pon the nodes executing the request, a reply is sent to the client.

4. There are f+1 replies received from different nodes with the same

result, where f represents the maximum number of potentially

faulty nodes awaited by the client.