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The pbft algorithm is mainly proposed to solve the Byzantine general problem. What is the Byzantine Generals Problem? Byzantium is located in Istanbul, Turkey, the capital of the ancient Eastern Roman Empire. The Byzantine Roman Empire had a vast territory. In order to achieve the purpose of defense, an army led by a general was stationed in each fief. Each army was separated far away, and the generals could only rely on messengers to transmit messages. During war, all generals in the Byzantine army must reach a consensus and decide whether there is a chance of winning before attacking the enemy's camp. However, there may be traitors and enemy spies in the army, and the decisions of the generals influence the generals to reach a consensus. When a general is known to be a traitor, the question of how the remaining loyal generals can reach a consensus is the Byzantine generals problem.
To make this problem have a solution, there is a very important premise, that is, the channel must be reliable. If the channel cannot be guaranteed to be reliable, then the Byzantine problem has no solution. Regarding the reliability of the channel, the issue of the two armies will arise. The conclusion of the issue of the two armed forces is that it is basically impossible or very difficult to try to reach agreement through communication over an unreliable communication link.
So if the channel is reliable, how to solve this problem? There are actually many ways to solve the Byzantine Generals problem. Next, I will introduce two big cows, both of whom have made outstanding contributions to solving the Byzantine problem.