The BFT Consent System – Byzantine Fault Tolerance

The BFT consent system was created with the aim of solving a problem in the consent of a blochchain network.

It solves the problem of the Byzantine generals.

Today with the introduction of the blockchain, new technologies have developed with it, but above all new problems.

With the birth of Bitcoin, in addition to the improvement of the system itself, there was a new concept “the consensus” that was not previously had.

In fact Satoshi, introducing the POW system, introduced what is the concept of decentralized consent system.

What is the BFT consent system

The problem of the Byzantine generals

The first to speak of the problem of the Byzantine generals were Lamport, Shostak and Pease in 1982, who described a scenario that was undergoing a war attack.

During an attack on an enemy city, they are more general headed by armies that are scattered in more places.

We must agree to attack the city in a coordinated and decisive manner.

But a problem arises, that all these generals must communicate with each other but they do not have the messaging of today but they have messengers.

sistema di consenso BFT

The problem arises when:

  • There may be corrupt generals;
  • There may be corrupt messengers.
  • Messages can be delayed, destroyed or lost in some way.

Not having the coordination of the attack, one could validate the attack itself which would turn into a loss.

This concept could be compared to the blockchain where Byzantine generals represent distributed nodes.

But then how can they reach consensus?

“A blockchain is” simply “a data structure governed by a distributed system with an unlimited number of participants in the consent process and an unknown number of Byzantine errors”

Consent would occur when at least 2/3 of the Byzantine Generals (NODI) are not corrupt and transmit the same information in a coordinated manner.

This means that if the remaining 1/3 of the Generals (NODES) are corrupted, the blockchain continues to function even if it transmits false signals.

In the BFT consent system, consent is obtained when 2/3 of the nodes function exactly.

If more than 1/3 are corrupted then at that point the attack would be 51% and this could validate the network.

This consensus system works when there are many nodes, so the number of corrupted nodes should be reduced.

Satoshi, introducing the POW system, has also introduced the BFT system as with the expensive mining process, it makes the network very difficult to corrupt and continues to function.

It could be said that the POW consensus system is not comparable to 100% of a BFT consent system but could be 70%.


This system can be useful when you have many nodes, and you want to reduce costs to maintain the network.

With the BFT consensus system the problem due to the possible corruption of the nodes would be solved, which could cause the attack to form at 51%.

The problem that links blockchain systems is precisely that of consensus, making the network scalable is unmanageable is one of the challenges facing today.

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