Byzantine Fault Tolerance

What is Byzantine Fault Tolerance?

When I first heard about "Byzantine Fault Tolerance" in 2017, it sounded to me like a riddle from the Middle Ages. In fact, the name comes from an old thought experiment, the Byzantine generals problem:

Imagine several generals want to attack a city. They can only communicate via insecure messengers. Some generals could be traitors and send false orders.
How can they still agree on a joint plan?

Solution:
→ Only if the majority makes the same decision is it valid. Individual mistakes or traitors cannot cause any damage.

Transferred to the blockchain:
BFT ensures that a decentrally organized network continues to function reliably, if some of the participants act incorrectly or maliciously.

Why is Byzantine Fault Tolerance so important?

Decentralized systems such as Bitcoin or Ethereum live from the fact that no one is in control alone. But what if someone in the network:

• spread a false transaction?
• claims a different version of the blockchain?
• simply goes offline?

Byzantine Fault Tolerance ensures that the system still works.
Only if a large majority confirms the same information will it be accepted.

Own experience:
When I was allowed to vote at a DAO (decentralized organization) for the first time in 2020, I saw live how important BFT is:
Despite various opinions and technical errors, the coordination was stable and reliable.

How does BFT work, simply explained?

Imagine a WhatsApp group with 20 friends who want to book a trip together.

• 15 votes for Italy 🇮🇹
• 4 want Spain 🇪🇸
• 1 does not react at all.

Although not everyone communicates perfectly, the majority decides: Italy.

This is exactly how BFT works:

• All participants exchange their opinions (or block data).
• Only if at least two thirds agree is a decision considered certain.

Comparison from everyday life:
A family outing also works when two children are talking nonsense - as long as mom and dad are in agreement.

Where is BFT used in the blockchain today?

• Cosmos (Tendermint protocol):
  Enables thousands of transactions per second through a particularly fast BFT-based consensus.
• Ripple XRP Ledger:
  Achieves transactions in seconds thanks to a customized BFT model - ideal for payment processing.
• Hyperledger Fabric:
  Large companies such as IBM and Walmart use this platform to document supply chains securely and transparently.

Advantages of BFT

✅ High security:
Networks can cope with up to a third of malicious participants.

✅ Fast transaction processing:
BFT systems do not require energy-intensive calculations like Bitcoin - this saves time and electricity.

✅ More environmentally friendly:
No mining required - much more sustainable than proof-of-work blockchains.

Disadvantages of BFT

❌ Scaling limit:
If a large number of participants are involved, communication becomes time-consuming.

❌ Attack risk with over 33 % errors:
If more than a third of the nodes work together, they can influence the system.

Everyday example for BFT

Another example that happened to me in 2021:
I was involved in a vote in the blockchain game "Axie Infinity". Despite technical failures on the part of some players, the vote came out clean because 70 % of the votes were cast correctly.
That was BFT experienced live!

Summary

Byzantine Fault Tolerance is like a protective mechanism that ensures that Decentralized systems work - even if some participants make mistakes or cheat.
Without BFT, blockchains would be prone to chaos and fraud.

Simply put:

"Even if not everyone at the table is honest, the group as a whole can still do the right thing."

Related articles:

• What is blockchain? Basics explained
• Proof of Stake explained simply
• Decentralization - the heart of the blockchain
• Hash value - the digital fingerprint of the blockchain

Sources:

• Hyperledger Fabric Documentation

About the author

Felix Rieger Verified

Founder & Lead Author · KryptoZukunft.com · Rheinmünster, Germany · since 2021

Since 2021, I've personally tested crypto exchanges, analyzed markets, and explained complex topics in an understandable way – Clear, honest, no hype. As the founder of KryptoZukunft.com, I have about 12 Stock Exchanges Tested, more than 100 journal articles written and help thousands of readers daily, to safely get into cryptocurrency. Not a financial advisor—but someone who has already made the mistakes and learned from them.

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