Byzantine Fault Tolerance (BFT): Decentralized Trust

Cryptography and security in decentralized systems have become fundamental topics in the information technology era. In this context, Byzantine fault tolerance (BFT) has emerged as a key concept to guarantee integrity and trust in decentralized networks, such as blockchains. In this article, we will explore what Byzantine fault tolerance is, the Byzantine generals problem, the relationship between BFT and blockchain, the types of Byzantine faults, as well as the advantages and limitations of this technology.

What is Byzantine Fault Tolerance (BFT)?

Byzantine Fault Tolerance, or BFT, is a concept in computing that refers to the ability of a decentralized system to resist failures and malicious behavior, ensuring that the system functions correctly. coherent and reliable manner even in the presence of nodes or actors that act incoherently or maliciously. In other words, BFT focuses on resistance to arbitrary failures or adversarial attacks in decentralized systems.

What is the Byzantine Generals Problem?

The problem of the Byzantine generals is a theoretical scenario that illustrates the need for Byzantine fault tolerance. Suppose a group of Byzantine generals surround an enemy city and must coordinate their attack or retreat. Some generals may be traitors and send false messages to other generals. The challenge is to ensure that loyal generals make a unanimous decision, even if some of them are dishonest or if messages between them are lost or manipulated. Byzantine fault tolerance addresses this problem, allowing generals to reach a reliable consensus in an untrustworthy environment.


Diagram of the problem of Byzantine generals. Source: Wikipedia.

Relationship between BFT and Blockchain

Blockchain technology, used in cryptocurrencies such as Bitcoin and Ethereum, is a prominent use case of Byzantine fault tolerance. In a blockchain network, participating nodes must agree on the state of the blockchain and valid transactions. Byzantine fault tolerance ensures that even if some nodes are malicious or faulty, the network can still reach a consensus and maintain the integrity of the data stored on the blockchain.

Types of Byzantine Faults

There are several types of Byzantine faults that BFT must address:

  1. Failures of omission: Some nodes may not respond or fulfill their responsibilities.
  2. Commission failures:Nodes can send incorrect or malicious information.
  3. Delay faults:Nodes can delay message delivery intentionally or unintentionally.
  4. Partition failures:The network can be divided into disconnected parts, making coordination difficult.
diagram scheme

Scheme of operation of a consensus model. Source: Kolokium Blockchain Technologies.

Advantages and Limitations of BFT

Advantages: Limitations:
Trust and Security: BFT ensures a high level of trust and security in decentralized systems by resisting failures and malicious attacks. Complexity: The implementation of BFT can be complex and require high computational cost.
Consistency: BFT systems maintain data consistency, which is crucial in financial and voting applications. Number of participants: Byzantine fault tolerance can become more challenging as the number of participating nodes in a network increases.
Scalability: BFT can be scalable and efficient, making it suitable for growing systems. Latency: BFT can increase decision-making latency due to the need for coordination between nodes.

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