What is Byzantine fault tolerance?

How does it ensure resilience in distributed systems?

Blockchain is powered by open networks of nodes where almost anyone can join anonymously without permission as long as they have the necessary hardware and software. However, there is always a possibility that some nodes may decide to launch an attack on the network by transmitting incorrect information about transactions to steal funds.

That's where Byzantine fault tolerance comes in. It ensures that such attacks are swiftly detected and prevented, allowing the network to function smoothly. Keep reading to find out more.

The Origin of Byzantine Fault Tolerance

The Byzantine Generals' Problem is a logical dilemma conceived in 1982 that highlights the difficulty in reaching a unanimous decision when a group of generals, each leading their army, need to agree on whether to attack or retreat. This problem arises due to communication issues that may occur between the different armies, which are located in various areas surrounding the intended target. For the decision to be executed successfully, all the generals must agree to the same plan and execute it synchronized.

To resolve this issue, each general must make an independent decision on whether to attack or retreat. Once the decision is made, it cannot be changed. All the generals must agree on the same decision, which must be executed seamlessly. This is easier said than done, as communication between the generals may be delayed, destroyed, or lost in transit, leading to confusion and potential failure. Even if all the messages are successfully delivered, one or more generals may decide to act maliciously and send false information to the others, which can further complicate matters.

In summary, the Byzantine Generals' Problem is a complex scenario highlighting the difficulties in achieving a consensus when multiple parties are involved and communication channels are limited.

When applied to blockchain contexts, envision each general as a network node, with the task of reaching a consensus on the system's current state. In essence, most participants in a distributed network must concur and act in unison to prevent catastrophic failure.

Byzantine Fault Tolerance (BFT) – A Shield for Distributed Systems

Byzantine fault tolerance refers to a system's ability to keep functioning even if some nodes within it fail or deliberately act in a problematic way. This is based on a well-known math problem called the Byzantine Generals' Problem. There are different ways to solve this problem and build a Byzantine fault-tolerance system.

One specific application of Byzantine fault tolerance is in blockchain technology. For a blockchain network to work effectively, it needs to resist malicious or faulty nodes. This is achieved through what's called a consensus algorithm. Different blockchain platforms use different consensus algorithms to ensure the network remains trustworthy and reliable.

How does BFT Consensus Algorithm work?

Achieving unanimous agreement among loyal and non-faulty nodes in a peer-to-peer network is essential for consensus. The core concept of BFT is evident in scenarios where all nodes in the network repeat incoming messages.

When a node successfully repeats an incoming message, it operates without issues or faults. Meaning there are no Byzantine Nodes. But what exactly is a Byzantine Node?

A Byzantine node is a traitor node within the network that may intentionally mislead or deceive other nodes. These deceitful nodes can also attempt to mislead the nodes involved in the consensus protocol. In a well-functioning blockchain network, Byzantine Fault Tolerance plays a crucial role in mitigating the impact of failures. Byzantine or malicious nodes can lead to specific challenges known as Byzantine failures.

There are two distinct types of Byzantine failures that users may encounter. The first type is purely technical, where even a slight error in a node's operation can affect its functionality, and in some cases, it might cease to respond or work altogether. The second type of Byzantine failure pertains to arbitrary node failures, where a node may exhibit the following traits:

• Failing to return a result.

• Providing responses with incorrect results.

• Intentionally providing misleading results for queries.

• Offering different results for the same query to different components of the system.

Byzantine Fault Tolerance, or BFT, effectively addresses these challenges by reducing the impact of malicious nodes. It helps protect the network from severe system failures and ensures the optimal functioning of the network. Essentially, BFT allows honest nodes and malicious nodes to coexist without compromising the network's performance.

Scallop Chain as a BFT chain

Scallop Chain is an exceptionally fast blockchain incorporating Byzantine fault tolerance, ensuring robust security and reliability. What sets it apart is its built-in KYC (Know Your Customer) and AML (Anti-Money Laundering) module integrated into the very fabric of its consensus mechanism at the protocol level. Scallop Chain is the world's first regulated blockchain built on the Cosmos framework on the Tendermint system.

Examples of BFT Algorithms

Numerous Byzantine Fault Tolerance (BFT) algorithms have been developed and put into practice across various blockchain networks. Examples of these BFT algorithms include Practical Byzantine Fault Tolerance (PBFT), Tendermint, and HotStuff.

PBFT

is among the earliest and most influential BFT algorithms. It operates on a leader-based approach with leadership rotating among nodes in a predetermined sequence. PBFT consists of four distinct phases: pre-prepare, prepare, commit, and reply.

Tendermint

is a consensus algorithm that combines PoS and BFT principles, ensuring consistency and allowing for the tolerance of up to 1/3rd of the faulty nodes. The Tendermint BFT consensus operates through a three-step process involving proposing, pre-voting, and pre-committing.

HotStuff

simplifies and optimizes the leader-based approach even further. It operates through three phases: prepare, pre-commit, and commit.

Blockchains like Hyperledger Fabric, Cosmos, and Facebook use these BFT consensus mechanisms. Scallop Chain uses the Tendermint consensus algorithm.

Conclusion

By implementing a BFT blockchain, organizations can be confident in building secure applications resilient to network state changes. If you are looking for an ideal BFT blockchain, Scallop Chain could be the one. It combines fast throughput with blazingly fast confirmations, ideal for scalable dApps and businesses. Scallop Chain is a promising blockchain to build a robust and resilient distributed system.