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3. Advanced Course

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  1. 1. What is Taproot?
  2. 2. Blockchain bridges – what are they?
  3. 3. What is the 51% attack on blockchain?
  4. 4. Zero-knowledge proof – a protocol that respects privacy 
  5. 5. What is EOSREX?
  6. 6. Mirror Protocol – what it is? 
  7. 7. What is DAO, and how does it work?
  8. 8. What is spoofing in the cryptocurrency market? 
  9. 9. What is digital property rights in NFT?
  10. 10. How to verify a cryptocurrency project – cryptocurrency tokenomics 
  11. 11. What is Ethereum Plasma?
  12. 12. What is Ethereum Casper?
  13. 13. What is Selfish Mining? 
  14. 14. How to create your own NFT? 
  15. 15. Schnorr signatures - what are they? 
  16. 16. What is Zk-SNARK and Zk-STARK? 
  17. 17. What is Proof of Elapsed Time (PoET)?
  18. 18. MimbleWimble - what is it? 
  19. 19. What are ETFs and what role do they play in the cryptocurrency market? 
  20. 20. What are synthetic assets? 
  21. 21. Definition of DeFi, and what are its liquidations?
  22. 22. New identity system - Polygon ID
  23. 23. What is Ethereum Virtual Machine (EVM) and how does it work?
  24. 24. Ethereum Foundation and the Scroll protocol - what is it?
  25. 25. What is Byzantine fault tolerance in blockchain technology?
  26. 26. Scalability of blockchain technology - what is it?
  27. 27. Interchain Security - new Cosmos (ATOM) protocol
  28. 28. Coin Mixing vs. Coin Join - definition, opportunities, and threats
  29. 29. Soulbound Tokens - what are they, and how do they work?
  30. 30. Definition of LIDO - what is it?
  31. 38. What is Web3 Infura?
  32. 39. Mantle - Ethereum L2 scalability - how does it work?
  33. 40. Polygon zkEVM - everything you need to know
  34. 41. What is Optimism (OP), and how do its roll-ups work?
  35. 42. What are RPC nodes, and how do they work?
  36. 43. SEI Network: everything you need to know about the Tier 1 solution for DeFi
  37. 44. Types of Proof-of-Stake Consensus Mechanisms: DPoS, LPoS and BPoS
  38. 45. Bedrock: the epileptic curve that ensures security!
Lesson 25 of 38
In Progress

25. What is Byzantine fault tolerance in blockchain technology?

Byzantine Fault Tolerance (BFT) is not the most discussed aspect regarding cryptocurrencies. However, it is the key to smooth operation of blockchain technology. First mention of the problem BFT are from 1982. In today’s lesson, we’ll tell you everything you need to know about it.

Byzantine generals problem – definition

As you know, the most important feature of cryptocurrencies is their decentralized nature. Distributed nodes verify and record transactions already in blockchain, which allows digital assets to operate without a central authority to manage them. To make this possible, cryptocurrencies need a proper way to reach consensus. And that’s where it shows up, Byzantine fault tolerance.

The issue of Byzantine fault tolerance is the ability of a computer system to continue its work even when its nodes fail or become infected with malware. The term itself comes from history and refers to the difficulty of Byzantine generals. This is a logical dilemma that requires a solution. Cryptocurrencies like maths!

Imagine a game where you have to defend a fortress. You are a general with your army. Most importantly, as a group, you must decide whether to attack the enemy or retreat. If democratically the decision is the same, you are successful. If there is no consensus or betrayal, the battle is lost, and the fortress is lost. These problems are Byzantine errors.

Let’s bring that to the present day. The general symbolizes a node in the network blockchain. The nodes must reach agreement, that is, the majority of members in a decentralized system must agree with each other and take the same action to prevent failure (defend the fortress) – that is, reach consensus. For the network to reach consensus, at least 66% of the nodes must be reliable and honest.

We had the historical and mathematical aspect, so now it’s time for the IT ☺ Byzantine fault tolerance is important because it tells us that the system can work even when some network components are not working properly.

As a curiosity, we will add that BFT is one of the most essential elements of blockchain technology that supports cryptocurrency transactions.

Byzantine fault tolerance for cryptocurrencies – how does it work?

Byzantine fault tolerance is the ability of a system, a computer network, to function even when some nodes are malfunctioning. It is important, especially in modern technology because it allows the system to function when part of it fails. So that blockchains can process transactions, the presence of BFT is necessary.

For the transaction to be validated on the network blockchain, the group of nodes serving it must reach an agreement. This is what we call a consensus algorithm, which is the rules they follow in network nodes to reach an internal agreement on the transaction.

Consensus is how a given blockchain achieves Byzantine fault tolerance. Every blockchain must work, even when some nodes provide false information or do not work properly.

We discussed consensus algorithms here. Most of them rely on some degree of Byzantine fault tolerance because any of them will work correctly even if not all nodes provide valid data.

Advantages of BTF

The first field is the ease and speed with which transactions can be carried out. BFT is fault-tolerant, which guarantees us an agreement and the time of our implementation transactions. So, it doesn’t matter how many nodes deliberately block our transaction or don’t want to reach an agreement.

The use of Byzantine fault tolerance is environmentally friendly. There is no high demand for computing power or energy consumption. What’s more, transactions do not require numerous verifications, thus the number of miners is reduced to a minimum.

BFT has lower power consumption than e.g. PoW. Blockchain technology, which uses Byzantine fault tolerance, does not require time-consuming and expensive processing, which reduces electricity consumption.

Disadvantages of BFT

The BFT system is vulnerable to cyberattacks and failures. Especially when most networks decide to behave incorrectly. We are talking about a 51% attack here. In addition to stealing assets, such action violates faith in blockchain and decentralized system for other users.


BFT is a basic tool that ensures the correct operation of the system, even when not all its participants have good intentions. It plays a critical role in the transformation of systems based on consensus. It may seem to us that the technical aspect of Byzantine fault tolerance applies only to computer scientists or cryptocurrency freaks. Nothing could be more wrong.