Byzantine Fault Tolerance (BFT)

A preventive counteraction against malicious attacks and software errors


How in the world of decentralized digitization everything function accordingly within an ecosystem without an authority? What if a node intended to misbehave, or just fell asleep and failed to act on an important message?



Of Nodes, Peers, and Consensus


The invention of the blockchain allowed for the trustless and permissionless functioning of subsequent digital creations such as cryptocurrencies, defi’s, and fintechs. To participate, a computer called a node or peer must follow the rules of the blockchain in a network, called a protocol. All other nodes rely on the protocol to make the general intent happen so that the goal is achieved. The decentralized system of the blockchain makes every node equal to each other, without a node having more power than the others. All they have to do is to agree to reach a consensus of following the protocol in order for all to enjoy its benefits. So as long as the majority rules where those who agree are greater than those who disagree. The protocol continues to function. But since there is not a manager or police to correct the inevitable failure, disobedience, or disagreement of some peers or nodes to the consensus, the Byzantine Fault Tolerant (BFT) was introduced into the blockchain system to keep it running despite the inevitables.



The Byzantine Fault Tolerant (BFT)


The concept of the Byzantine Fault Tolerant was borne out of the inspiration from the 1982 Byzantine General’s Problem paper published by Leslie Lamport, Robert Shotak, and Marshall Pease. It alludes to the hardships of achieving consensus within a decentralized ecosystem. Before an impending battle, the Byzantine generals who are in command of their own army battalions and are manning different locations around the city they intend to attack need to reach an agreement.


-They can only agree together to attack or retreat by sending their messages through couriers between them.

-A general’s decision is final.

-All generals must agree to a common decision and execute in synchronicity.


But it is highly probable that some generals or couriers may be traitors who are capable of altering messages or sending malicious responses to sabotage the cause. Messages may also be destroyed or lost along the way. The good-intentioned generals must find ways and means to reach out to one another to achieve a consensus to overcome the odds of miscommunication and execute the plan in coordination. If not, the plan can end in failure.



The Blockchain Dilemma


This is a kind of dilemma that can be applied in the context of blockchain technology where the generals represent the nodes, and the couriers are the messaging protocols. The majority of the nodes within the distributed network environment must agree and execute synchronized actions to prevent a system failure. There must be at least two-thirds of reliable nodes to achieve consensus to keep the distributed network running efficiently. Without the majority 2/3, the system can become vulnerable to failures, and even a 51% attack.

The Byzantine Fault Tolerance is a fundamental property of a blockchain architecture that can protect its functions even if there is an uprising of not more than one-third of malicious nodes. Proof-of-Work and Proof-of-Stake are examples of such consensus protocols.



The Genius of Satoshi Nakamoto


There are different approaches to solve Byzantine issues, and common among them is the Proof-of-Work adopted and modified by Satoshi Nakamoto in order to create Bitcoin as a BFT system. With the Bitcoin protocol laying out the basic rules of the system, it was the Proof-of-Work consensus algorithm that defined how the rules are to be followed to reach consensus. While PoW enlists itself as not that tolerant to Byzantine faults, it has proven itself as most secure if not reliable due to the methodical cryptographics and costly mining mechanisms that accompany Bitcoin. By that alone, Satoshi Nakamoto’s PoW consensus algorithm design is genius to a fault.





Satoshi Nakamoto’s brainchild, Bitcoin, remains to be the bar upon which blockchain consensus protocols are designed. His PoW design built into the Bitcoin protocol is solving the Byzantine Generals Problem in the presence of malicious nodes, and achieving majority agreements even without a centralized authority.

Aside from PoW and PoS, which are by far the more famous, other consensus protocol mechanisms are on the rise like Practical Byzantine Fault Tolerant (PBFT), Delegated Proof of Stake (DPoS), Directed Acyclic Graphs (DAG), Proof of Elapsed Time (PoET).

Beyond blockchain, BFTs are also used in other sensitive industries such as in nuclear power, space, and aviation. Where security and safety play a major role, large networks of interconnecting sensors and computers acting as nodes must be as reliable as possible at all times so that they function at high levels even in the presence of faulty nodes.

Looking into the future, researchers and developers will keep on doing what they do best to perfect such BFT systems as digital organizations of emerging classes need to be safe and secure amid recurring Byzantine faults and issues.



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