Byzantine Generals Problem
Problem:
How can you get a group of generals, each in charge of their own army, to agree on a plan of attack when some of the generals may be traitors?
The Byzantine generals problem is a classic problem in distributed systems that illustrates the challenges associated with achieving consensus in a distributed system. The problem is named after the Byzantine Empire, which was notorious for its internal strife and civil wars.
The Byzantine generals problem is relevant to a wide range of distributed system applications, such as distributed databases, distributed file systems, and peer-to-peer networks.
The following videos provides a very easy to understand explanation about the Byzantine generals problem.
Solution:
The Byzantine generals problem has been solved using a variety of techniques, including voting, cryptography, and game theory.
Voting:
One way to solve the Byzantine generals problem is to use voting. Under this approach, each general casts a vote for the plan they prefer. The plan with the most votes is then selected as the final plan.
However, voting can be vulnerable to attack by traitorous generals. For example, a traitorous general could cast multiple votes or vote against their own army.
Cryptography:
Another way to solve the Byzantine generals problem is to use cryptography. Under this approach, each general encrypts their vote using a shared key. The votes are then tallied and the plan with the most votes is selected as the final plan.
However, cryptography can be vulnerable to attack by traitorous generals. For example, a traitorous general could forge votes or refuse to decrypt the votes.
Game theory:
A third way to solve the Byzantine generals problem is to use game theory. Game theory is a branch of mathematics that studies the interaction between different parties in order to gain an advantage.
Under this approach, each general calculates the best course of action based on the actions of the other generals. The plan that results in the most benefit for the generals is then selected as the final plan.
This approach is resistant to attack by traitorous generals because each general has an incentive to act in their own best interest.
However, game theory can be complex and difficult to implement.
