Byzantine Fault Tolerance is a system feature that allows consensus to be reached in the event of failures, such as sent data not reaching the recipient or being sent incorrectly.
Byzantine fault tolerance describes the property of a system that allows it to solve this problem and build consensus harmoniously, regardless of whether some nodes agree with other nodes or not. Byzantine fault tolerance forms the basis of algorithms that allow the Byzantine generals problem to be solved without losing data or compromising data integrity. BFT succeeds when consensus mechanisms such as Proof of Stake or Proof of Work and most of the nodes remain loyal to the system.
The consensus algorithms used in the blockchain ecosystem are a fundamental element for creating a decentralized network. Most of the nodes agree on the transaction correctness and this ensures the sustainability of the network. Byzantine fault tolerance means that in some cases, even if nodes fail or are malicious, others continue the verification process. BFT prevents potential incidents such as double-spending or 51% attack.
How Did the Problem of Byzantine Generals Arise?
The Problem of the Byzantine Generals is an article published in 1982 by Leslie Lamport, Robert Shostak and Marshall Pease. The published article emphasized that two thirds of the generals had to be loyal for consensus to form. Byzantine fault tolerance should not be a problem as long as the number of malicious generals does not exceed one third.
It is based on the example of Byzantine generals setting up an siege around an enemy city and communicating with each other only through intermediary messengers. When a decision has to be made whether to attack the city or retreat, they act without consensus because some of them are malicious. Attacks or retreats are irrelevant as long as there is no cohesion or consensus among the generals.
Therefore, generals should keep three objectives in mind:
- Each general must decide whether to attack or retreat.
- They must not change their decision after it has been made.
- All the generals must agree on the same decision and implement it at the same time.
How Does Byzantine Fault Tolerance Work?
In the blockchain structure, generals represent nodes. For transactions to take place in the blockchain network, the nodes in the network must reach a consensus. As a result of consensus, proven data is added to the blocks.
Byzantine fault tolerance is neutral, recognizing that some nodes in the network may or may not be faithful. It does not use a strictly true or false statement about the data. BFT requires consensus from the majority of network participants, recognizing that data may be the result of erroneous or malicious behavior.
What Are Blockchain Consensus Algorithms?
Consensus algorithms are systems by which any blockchain ecosystem achieves consensus. The most commonly known and used consensus algorithms are Proof of Work (PoW) and Proof of Stake (PoS) mechanisms.
Proof of Work allows new blocks to be added and verified on the blockchain network after complex mathematical problems have been solved by miners. PoW is considered secure because of its expensive prerequisites. Proof of Work is about how to follow these rules in the process of verifying and validating transactions to achieve consensus. The Proof of Work algorithm created by Satoshi Nakamoto is considered one of the best solutions to Byzantine bugs.
Proof of Stake is a consensus mechanism used to process transactions and generate new blocks on the blockchain. Proof of Stake is used to ensure the integrity of the blockchain network. With the Proof of Stake mechanism, validators verify block transactions according to the amount of cryptocurrencies they stake. Proof of Stake was created as an alternative to the Proof of Work mechanism.
