Byzantine Fault Tolerance in Blockchain

In the previous lesson, you learned the challenges with consensus mechanisms such as proof-of-work. You also learnt how 51% attack can cause the blockchain network not to behave properly. There is one more problem similar to 51% attack known as Byzantine Generals problem. Let’s hear from Shebin what this problem is.

The Byzantine Generals problem occurs when a malicious node propagates wrong message or tampered transactions in the network that could compromise the security of data in the blockchain network. The blockchain network needs to be tolerant to such activities and needs to ensure that all the transaction data in the network is tamper free. Such networks are called as Byzantine Fault Tolerant Networks and they use the Byzantine fault tolerant (BFT) consensus.

Let’s look at the BFT consensus in the upcoming video.

In the previous video, you learnt that for a network to be BFT, the number of malicious nodes in the network should be less that 1/3rd of the total nodes in the network. Whenever a node receives two conflicting messages, it goes for a majority vote and accepts the message that comes from the majority number of nodes. To ensure that the correct message is accepted by the nodes in the network, the total number of malicious nodes needs to less than 33.33% or 1/3rd of the network. Proof-of-work is a BFT consensus mechanism provided the 51% attack and pool mining does not happen.

To overcome the challenges faced by proof of work, there are other mechanisms being devised. Let’s have a look at one of them.

The proof of work is a very energy intensive mechanism and requires a lot of computational power. Only one node comes out as a winner and the rest of the energy used by other nodes is wasted in the proof of work mechanism. The consensus mechanisms are eveolving and one of the methods to overcome the challenges of proof of work is to choose a leader node based on the stake in the network. It is very unlikely for a node to be malicious if it has the maximum stake in the network.