Since the birth of Bitcoin as a peer-to-peer electronic cash system in 2008, many other digital currencies have gradually emerged, and each digital currency has its own specific mechanism. But almost all digital currencies have one thing in common, which is the core architecture of blockchain.

In most cases, blockchains are designed to be decentralized, electronic ledgers maintained by a distributed network of nodes. Blockchain systems therefore allow financial transactions to be executed completely transparently and reliably without middlemen. Digital currencies are gradually replacing traditional bank payment systems that require high trustworthiness.

As with most distributed computing systems, participants in a digital currency network need to regularly discuss and agree on the current state of the blockchain. This is what we call consensus. However, achieving consensus in a secure and efficient manner in a distributed network is no easy task.

So, how can a distributed network of computer nodes agree on decisions in situations where some nodes may malfunction or behave dishonestly? This is the root of the so-called Byzantine Generals Problem, which gave rise to the concept of Byzantine Fault Tolerance.

What is the Byzantine Generals Problem?

Simply put, in 1982, the Byzantine Generals Problem was considered a logical dilemma that illustrated the communication problems a group of Byzantine generals could have when trying to agree on a unified opinion on their next move.

This dilemma assumes that each general has his own army, each located at a different location around the city they intend to attack. These generals need to agree on whether to attack or retreat. It does not matter whether it is an attack or a retreat, as long as all the generals reach a consensus, that is, coordinate and decide to execute it together.

Therefore, we can consider the following conditions:

• Each general must make a decision: attack or retreat (yes or no);
• Once made A decision cannot be changed after it is made;
• All generals must agree on a unified decision and execute it simultaneously.

The above communication problem involves the fact that one general can communicate with another general only through messages sent by intelligence agents. Therefore, the core challenge of the Byzantine Generals Problem is that information may somehow be delayed, corrupted, or lost.

Furthermore, even if the message is successfully delivered, one or more generals can choose to act maliciously (for any reason) and send fraudulent messages to confuse other generals, causing the operation to fail.

If we map this dilemma to the blockchain, each general represents a network node, and the nodes need to reach a consensus on the current state of the system. In other words, a majority of participants in a distributed network must agree and perform the same actions to avoid failure.

Therefore, the only way to achieve consensus in these types of distributed systems is to have at least two-thirds of the network nodes that are reliable and honest. This means that the system is vulnerable to failures and attacks (such as 51% attacks) if a majority of nodes in the network decide to act maliciously.

Byzantine Fault Tolerance (BFT)

Simply speaking, Byzantine Fault Tolerance (BFT) is able to resist the Byzantine Generals Problem. A series of failed system properties. This means that a Byzantine fault-tolerant system can continue to operate even if some nodes fail or behave maliciously.

There are many possible solutions to the Byzantine Generals Problem, and therefore, there are many ways to build a Byzantine Fault Tolerant system. Likewise, blockchains have various different ways to achieve Byzantine fault tolerance, which is what we call consensus algorithms.

Blockchain consensus algorithm

We can define the consensus algorithm as the consensus reached by the blockchain network. mechanism. The most common examples are Proof of Work (PoW) and Proof of Stake (PoS). Here we take Bitcoin as an example.

The Bitcoin protocol sets out the main rules of the system, and the proof-of-work consensus algorithm explains how these rules are followed to achieve consensus (for example, during verification and validation of transactions).

Although the concept of proof of work is earlier than digital currency, Satoshi Nakamoto modified the original version and developed an improved proof of work algorithm that can generate Bitcoin as A Byzantine Fault Tolerant System.

Please note that this proof-of-work algorithm is not fully resistant to Byzantine faults, but due to the high-cost mining process and underlying encryption technology, proof-of-work has proven to be one of the most reliable in blockchain networks. Safe and reliable method. In this sense, the proof-of-work consensus algorithm designed by Satoshi Nakamoto is considered by many to be one of the most sophisticated solutions to Byzantine Fault Tolerance.

Conclusion 

The Byzantine Generals Problem is an interesting dilemma that ultimately gave rise to Byzantine fault-tolerant systems that are being widely used in a variety of scenarios . In addition to the blockchain industry, some use cases for Byzantine Fault Tolerance systems also include the aviation, aerospace, and nuclear power industries.

In the field of digital currency, having efficient network communication and a good consensus mechanism are crucial for any blockchain ecosystem. Securing these systems requires ongoing efforts, and there are limitations (such as scalability) that existing consensus algorithms have not been able to overcome. Nonetheless, proof-of-work and proof-of-stake are effective methods for Byzantine fault-tolerant systems, and their potential applications will inspire more innovation.