What Is Byzantine Fault Tolerance? How Do You Solve Byzantine Generals’ Problems 2023?

What Is Byzantine Fault Tolerance

Byzantine fault tolerance is a system design paradigm used in distributed computing systems to achieve consensus in the presence of Byzantine failures. A Byzantine failure is a type of failure that occurs when components of a system behave in an unexpected or malicious way. In a distributed system, such as a blockchain network, consensus is achieved when all nodes in the system agree on the state of the system. Byzantine fault tolerance is necessary to ensure that the system can continue to function correctly even in the presence of Byzantine failures.

What Is Byzantine Fault Tolerance (BFT)?

What Is Byzantine Fault Tolerance (BFT)?
What Is Byzantine Fault Tolerance (BFT)?

In distributed computer systems, Byzantine fault tolerance (BFT) is the ability to handle component failures in such a way that the system as a whole can continue to operate correctly. The term comes from the Byzantine Generals’ Problem, a thought experiment in game theory that illustrates the difficulties that can arise when different components of a system have conflicting information.

BFT is an important consideration in the design of distributed systems, because even a single component failure can jeopardize the safety of the entire system. For example, consider a distributed database that is replicated across multiple servers. If one of the servers fails, the others can continue to operate correctly and keep the database consistent. However, if two or more servers fail, they may end up with different versions of the database, which could lead to inconsistency and data loss. BFT algorithms allow a distribute

d system to continue to function even in the face of component failures.

They do this by ensuring that all components have the same information, and by providing mechanisms for detecting and handling failures. There are many different BFT algorithms, each with its own trade-offs in terms of performance, complexity, and security. Some of the more well-known BFT algorithms include Paxos, Raft, and ZAB.

Why is Byzantine Fault Tolerance so Important?

Byzantine Fault Tolerance is important in computing because it means that a system can continue to function even if certain components fail. Anything that uses a computing system, such as an airplane or a space probe, must be able to function even when not all of its nodes are fully operational.

Another reason to learn about cryptocurrency is if you invest in cryptocurrency stocks or individual coins. Byzantine Fault Tolerance is an essential component of blockchains that process cryptocurrency transactions.

How does Byzantine Fault Tolerance relate to blockchain?

Blockchain technology is used to validate, process, and record transactions in cryptocurrencies. A group of nodes must agree that a transaction is valid before it can be completed. Each blockchain network has a consensus algorithm, which is a set of rules that its nodes must follow in order to reach an agreement on transactions.

The consensus algorithm is responsible for a blockchain’s Byzantine Fault Tolerance. Due to the decentralized nature of cryptocurrencies, each one faces a large-scale version of the Byzantine Generals Problem. The blockchain must be able to function even if some nodes are not functioning properly or are providing false information.

Bitcoin (CRYPTO:BTC) initially attempted to solve this problem using proof of work. Miners must solve complex equations using specialized computer equipment in order to use this consensus algorithm. The first miner to correctly solve an equation wins the right to add a block of transactions and earn rewards. You’ve wasted your time and energy if you don’t produce the correct data.

Proof of stake is another popular type of consensus algorithm. It entails validators staking their cryptocurrency, which means storing it in a wallet in exchange for the right to verify transactions. If the protocol selects you to add a block to the blockchain, you will be rewarded in cryptocurrency. However, if you attempt to approve invalid transactions, you will lose some or all of your staked cryptocurrency.

Both of those consensus algorithms have some Byzantine Fault Tolerance because they can function properly even if some nodes provide incorrect data.

What is BFT in Crypto?

What is BFT in Crypto?
What is BFT in Crypto?

Byzantine Fault Tolerance is extremely important in crypto, specifically blockchain technology. When the Byzantine Generals’ Problem is applied to crypto, the generals are the nodes. All nodes in a blockchain network must communicate with one another in order to reach a consensus, which leads to methods known as consensus algorithms.

There are several approaches to achieving Byzantine Fault Tolerance. As a result, various consensus algorithms exist in the blockchain space, each with its own solution to the problem for maximum efficiency.

Bitcoin, with its Proof of Work consensus algorithm, was among the first in crypto to achieve Byzantine Fault Tolerance. Proof of Work, along with the success of Bitcoin, has proven to be one of the most secure and reliable solutions to this problem since its introduction in 2008.

How does Practical Byzantine Fault Tolerance work?

How does Practical Byzantine Fault Tolerance work?
How does Practical Byzantine Fault Tolerance work?

Practical Byzantine Fault Tolerance (pBFT) is a consensus algorithm developed in the late 1990s by Barbara Liskov and Miguel Castro to address issues with existing Byzantine Fault Tolerance solutions.

In general, pBFT works by first designating one node as the primary (leader) node and the others as secondary (backup) nodes. If the current node fails, any node can become the primary.

Furthermore, a pBFT system can function only when the maximum number of malicious nodes is less than or equal to one-third of all nodes in the system.

The pBFT consensus rounds are divided into four stages:

  • Request: The client sends a request to the primary (leader) node.
  • Pre-prepare: The primary (leader) node broadcasts the request to all the secondary (backup) nodes.
  • Prepare: The nodes (primary and secondary) perform the service requested.
  • Commit: The reply is sent to the client if it is valid.

Pros and cons to practical Byzantine Fault Tolerance

Pros and cons to practical Byzantine Fault Tolerance
Pros and cons to practical Byzantine Fault Tolerance

Practical Byzantine Fault Tolerance has several advantages:

  • Because there are no miners solving complex equations for each block of transactions, it does not necessitate significant computing power or energy consumption. As a result, it is far more environmentally friendly than proof of work.
  • Multiple confirmations are not required for transactions. If all nodes agree on a block of transactions, it is immediately confirmed.
  • Because all nodes can participate, they can all share in the rewards. There isn’t as much variation in which nodes earn rewards as there is in proof of work and proof of stake.

No solution is perfect, and practical Byzantine Fault Tolerance has some significant drawbacks:

  • It is vulnerable to Sybil attacks (named after a book about a woman with multiple personalities), in which one party gains control of a large number of nodes. The greater the number of nodes, the more difficult it is to launch a Sybil attack.
  • Every step of the process necessitates communication between nodes. This takes time, which can be an issue in terms of scalability.

What is the Byzantine Generals’ Problem?

What is the Byzantine Generals’ Problem?
What is the Byzantine Generals’ Problem?

The Byzantine Generals’ Problem is a problem in computer science that deals with the issue of getting disparate parties to agree on a common strategy. The problem is named after the Byzantine Empire, which was beset by civil wars in which different generals were often forced to choose between conflicting orders.

The Byzantine Generals’ Problem was first presented in 1982 in a paper by a group of Microsoft Research employees. The issue was clearly stated as follows:

“Imagine that several divisions of the Byzantine army are camped outside an enemy city, each division commanded by its own general. The generals can communicate with one another only by messenger. After observing the enemy, they must decide upon a common plan of action.

However, some of the generals may be traitors, trying to prevent the loyal generals from reaching an agreement. The generals must decide on when to attack the city, but they need a strong majority of their army to attack at the same time.

The generals must have an algorithm to guarantee that (a) all loyal generals decide upon the same plan of action and (b) a small number of traitors cannot cause the loyal generals to adopt a bad plan. The loyal generals will all do what the algorithm says they should, but the traitors may do anything they wish. The algorithm must guarantee condition (a) regardless of what the traitors do. The loyal generals should not only reach agreement but should agree upon a reasonable plan.”

Although similar to the Two Generals’ Problem (Two Generals’ Paradox), the Byzantine Generals’ Problem is a more general version. The Byzantine Generals’ Problem can impose more variations in a more complicated manner. For example, messengers may fail to deliver the message on the way or may purposefully alter the original content.

How Do You Solve Byzantine Generals’ Problems?

How Do You Solve Byzantine Generals' Problems?
How Do You Solve Byzantine Generals’ Problems?

Implementing a protocol with fault-tolerant mechanisms can solve the problem. When faced with uncertainty, following a procedure established by the generals is the best way to make decisions.

As a result, because nothing can be guaranteed, it becomes probabilistic rather than deterministic. That is especially true when there is little direct communication between peers and each is self-contained. There is a physical separation between them because each general is in a different location.

Blockchain: The solution for the Byzantine general problem

The Byzantine general problem can be solved with a blockchain. It’s about giving people a safe way to communicate in an uncertain world. Most transactions involve strangers who don’t know or trust each other.

Each person waits for orders to attack or defend. There are no middlemen to arbitrate the attack; you decide alone. A blockchain can be trusted without trusting every individual. A network of nodes agrees on the truth before recording it. If a general is unsure about a message, other generals can verify it.

Once one node records it, all other nodes receive a copy, making the information redundant. PoW consensus achieves this. Because information isn’t always accurate, bad actors will try to game the system. As a public system, a blockchain has fault-tolerant mechanisms and security. Cryptography was needed to prevent message alteration.

The system provides key pairs for digitally signing a message to prove its origin. Authenticated messages are recorded for accountability and transparency.

How does Bitcoin solve the Byzantine generals problem?

Bitcoin was the first realized solution to the Byzantine generals problem in terms of money. Before Bitcoin, many plans and projects attempted to create money that was independent of the government, but they all failed in some way.

As a monetary system, Bitcoin requires the ability to handle ownership and avoid double-spending. To accomplish this in a trustless manner, Bitcoin employs a blockchain, or a public, distributed ledger, which stores a history of all transactions. In the Byzantine generals analogy, the blockchain is the truth on which all parties must agree.

If all nodes in the Bitcoin network could agree on which transactions occurred when and in what order, they would be able to verify Bitcoin ownership and create a working, trustless monetary system without the need for a centralized authority.

Proof-of-Work (PoW) and the Byzantine generals problem

Proof-of-Work (PoW) and the Byzantine generals problem
Proof-of-Work (PoW) and the Byzantine generals problem

In cryptographic security, a transaction is secured in a block that is linked to other blocks by its hash value. All hashes can be traced back to an initial block, which is the root of all hashes. The blockchain is a system that uses a Merkle Tree to validate hashes generated by the genesis block.

Every valid block in the network stems from the first block, also known as the genesis block. As part of a PoW consensus method, miners validate blocks and compete with other miners to solve cryptographic puzzles to produce blocks.

Bitcoin overcame the Byzantine generals problem and established a clear, objective rulebook for the blockchain by employing a proof-of-work consensus mechanism. To add information to the blockchain, known as blocks, a network member must publish proof that they worked hard to create the block. This work is expensive for the creator, which incentivizes them to share accurate information.

Because the rules are objective, there can be no disagreement or tampering with the information on the Bitcoin network. Both the system for determining who can mint new Bitcoin and the laws governing which transactions are valid or invalid are goals. Furthermore, once a block has been added to the blockchain, it is impossible to remove it, rendering Bitcoin’s history unchangeable.

As a result, miners who are similar to generals in Satoshi’s version of the blockchain solve the Byzantine generals problem. Each node is in charge of validating transactions, which are analogous to messages delivered to generals. Bad actors (for example, hackers) who intend to steal messages or harm the network can be viewed as the enemy.

Because of cryptographic security, hackers can’t easily attack the blockchain. Messages or transactions are hashed to prevent manipulation. Satoshi increases probabilities by having miners compete to validate blocks. This makes it decentralized because no single miner can monopolize validation. Miners compete to solve a riddle using their hash rate. Higher hash rates mean more likely puzzle solution. When a miner broadcasts the puzzle’s solution to the network, all other miners must validate or reject it. A difficulty target must be the correct value or less.

Bitcoin network members can agree on blockchain status and transactions at any time. Each node verifies blocks and transactions based on the proof-of-work criterion. All network nodes will ignore misleading information broadcast by a network member. Each node can verify all network information, making Bitcoin a trustless system.

Decentralized blockchain means no single point of failure. Blocks are stored in a replicated distributed database. This redundancy ensures that no single malfunctioning computer can bring down the entire system. It’s like having multiple messengers in case one is ambushed. Because other messengers will copy it, it won’t be lost.


Frequently Asked Questions

Is Tendermint BFT?

Tendermint, introduced in 2014, is the first Proof-of-Stake consensus algorithm derived from the Practical Byzantine Fault Tolerant (PBFT) algorithm. As a result, it is classified as a BFT Proof-of-Stake consensus algorithm.

Is Proof of Stake Byzantine Fault Tolerance?

As previously stated, blockchain technology necessitates consensus algorithms in order to achieve Byzantine Fault Tolerance. Proof of Stake, like Proof of Work, can satisfy Byzantine Fault Tolerance requirements.

Is Ethereum Byzantine Fault Tolerance?

Ethereum currently employs the Proof-of-Work consensus algorithm, which is similar to that employed by Bitcoin. Ethereum’s network will be converted to Proof-of-Stake in the future. In any case, Ethereum is still capable of meeting Byzantine Fault Tolerance.


Byzantine Fault Tolerance is a type of fault tolerance that is designed to deal with faulty nodes in a distributed system. It is based on the assumption that there are Byzantine generals, each with their own army, trying to conquer a city. In order to be successful, they need to coordinate their attacks. However, some of the generals may be traitors, and so the others need to be able to identify the traitors and exclude them from the coordination.

Byzantine Fault Tolerance is a very effective way of dealing with faulty nodes in a distributed system. It is based on a simple but powerful idea, and it has been shown to be robust in practice.

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