BFT (J20)

They don't care about the group decision. They're only looking out for themselves, and in fact, they don't want to go fishing or play console at all. They also don’t want the event to succeed, and for any event to be successful, all the kids must be present.

These treacherous kids start convincing some others to play console instead of going fishing. Then, they go to a different group of kids and tell them to go fishing instead of playing console.

If each group of kids does what they’ve been told by these troublemakers, the event will fail. This is an analogy to explain the Byzantine Generals Problem.

When you hear BFT, just think of the special property of a blockchain that allows it to continue working properly, even if some nodes are faulty or malicious.

Now, let’s get technical…

The Byzantine Generals Problem was hypothesized by Leslie Lamport, Robert Shostak, and Marshall Pease in 1982.

Technically, Byzantine Fault Tolerance (BFT) refers to the ability of a distributed system to tolerate Byzantine faults.

A Byzantine Fault occurs when a distributed system receives conflicting information, making it impossible to reach a decision or take a unified action.

The Byzantine Generals Problem is a well-known analogy used to explain this fault.

Imagine multiple generals, each commanding an army, planning to either invade a city or retreat.

Success requires all generals to act together—either invade or retreat—but the challenge arises when some generals act maliciously, sending conflicting orders.

Some might tell others to invade while planning to retreat themselves. To prevent failure, the loyal generals must find a way to agree on a plan, even if some messages are false.

In blockchain systems, the generals represent computers or nodes, while the malicious actors or faulty components are analogous to the traitorous generals.

A system that continues to function correctly, even when some nodes fail or act maliciously, is said to have Byzantine Fault Tolerance.

In centralized systems, BFT is unnecessary because decision-making is controlled by a central authority.

However, in decentralized systems, like blockchains, where no central authority exists, BFT is essential to keep the network running smoothly, even when some participants try to disrupt it.

There are many ways to solve the Byzantine Fault (or Byzantine Generals Problem), especially in blockchain systems, where consensus mechanisms are widely used.

Here are some notable solutions:

1. Practical Byzantine Fault Tolerance (pBFT)
2. Delegated Byzantine Fault Tolerance (dBFT)
3. Federated Byzantine Fault Tolerance (fBFT)
4. Asynchronous Byzantine Fault Tolerance (aBFT)
5. Synchronous Byzantine Fault Tolerance
6. Tendermint Consensus
7. Q/U Protocol
8. Honey Badger BFT

Practical Byzantine Fault Tolerance (pBFT)

This solution is common in blockchain technology today. Here, when a node receives a transaction, it broadcasts the transaction to other nodes.

If the majority of nodes confirm that the transaction is valid, it gets validated and added to the blockchain.

pBFT operates efficiently when fewer than one-third of the nodes are faulty or acting maliciously.

Delegated Byzantine Fault Tolerance

In dBFT, not every node needs to agree on every transaction. Instead, the network elects a smaller group of representatives (validators) to handle transaction validation.

These representatives are chosen by the nodes and can be voted out if they act maliciously. This system is democratic and reduces the complexity of reaching consensus across large networks

Federated Byzantine Fault Tolerance

fBFT works based on trust groups. Smaller groups, called federations, are established within the network.

Each federation reaches consensus internally, and then the different federations coordinate to reach consensus across the entire network. fBFT simplifies the consensus process by breaking it down into manageable, smaller groups.

Asynchronous Byzantine Fault Tolerance

aBFT is used in systems where there is no guaranteed communication time. Even when messages between nodes are delayed or lost, consensus still needs to be reached.

aBFT employs sophisticated algorithms to handle these delays, making it more flexible than Synchronous Byzantine Fault Tolerance, which requires strict time guarantees for message delivery.

Synchronous Byzantine Fault Tolerance

In contrast to aBFT, Synchronous Byzantine Fault Tolerance requires a reliable communication system, where nodes work based on a known, guaranteed message delay.

Nodes act within this time limit, and if a message delay exceeds the expected timeframe, the system can respond to prevent faults from disrupting the network.

Wow…we've come a long way.

I hope this article has been able to educate you about the not-so-talked-about Byzantine Fault that Blockchains overcome in order to serve us the way it does.

Do you think this solutions are reliable enough to mitigate the risk posed by the Byzantine Generals Problem?

Thank you for stashing knowledge for yourself.