Byzantine Fault Tolerance (BFT)

What does Byzantine Fault Tolerance (BFT) mean?

Byzantine Fault Tolerance (BFT) is a commonly used term to discuss the security of a network.

Main Idea:

Byzantine Fault Tolerance has been the most commonly used term to discuss the security of a blockchain network. It makes sense as a measure of security when certain assumptions about the attacker(s) abilities are true. These assumptions have failed in practice, so other forms of security should be considered as well.

A Traditional Model of Security:

Under a security model of Byzantine Fault Tolerance (BFT), a Byzantine node is another name for a malicious node (one that does not follow protocol). BFT is a measure of how tolerant the network is to the presence of Byzantine nodes. Specifically, BFT is the maximum percentage of malicious nodes that can be in a network while still having the blockchain (or other processes the network supports) work according to its protocol.

When the assumptions of a BFT security model are satisfied, then the higher the BFT, the more secure the network is under the types of threats considered. For example, a blockchain based on a Proof of Work – longest chain rule protocol, such as bitcoin, is considered 50% BFT. That is, the blockchain follows protocol as long as it is not threatened by a majority (51%) of the hashing power.

Used in a Sentence:

The Byzantine Fault Tolerance model of security does not account for other problems in the construction of a blockchain, such as the failure of a node to include valid transactions in a block at the time those transactions were submitted.

Last Updated: March 21, 2021