Byzantine fault tolerance is a measure of the ability of a distributed system to continue operating even if one or more of its components fails.
A defining characteristic of blockchains such as Bitcoin or Ethereum is that they are run by open networks of nodes, which anyone can join pseudonymously without permission, provided they have the necessary hardware and software. They are decentralized, so there is no central entity coordinating activities. Instead, rules and communication protocols govern the operation of the network and the methods by which nodes reach consensus.
But what if a node, or group of nodes, decides to attack the network by transmitting information about false transactions in an attempt to steal funds? The ability of the network to resist such an attack and continue operating uninterrupted is known as Byzantine fault tolerance.
The term Byzantine fault tolerance originates with the Byzantine Generals’ problem, a game theory problem that poses the dilemma faced by a hypothetical group of Byzantine generals stationed outside an enemy city who wish to coordinate an attack. To do so, they need a secure means of communication that will allow them to identify whether other generals are transmitting unreliable information, possibly in an attempt to subvert the attack. It’s a simple analogy, but it sums up the challenges facing distributed system developers very well.
The Byzantine Generals’ problem was first outlined in a 1982 paper by three computer scientists, Leslie Lamport, Robert Shostak, and Marshall Pease. The term “fault” was already common parlance to describe the kind of failure described by the Byzantine Generals’ problem; thus, Byzantine fault tolerance became the term to describe resilience to such failures.
In the 1990s, researchers developed an algorithm called “Practical Byzantine Fault Tolerance” (pBFT) which enabled nodes in a network to reach consensus without relying on a central entity to coordinate. However, it had limited practical applications since the time taken to reach consensus increased exponentially compared to the rate of network growth.
In 2008, Satoshi Nakamoto published the Bitcoin white paper, which proposed a novel Byzantine fault-tolerant consensus method based on the proof of work (PoW) protocol. Since the launch of Bitcoin, blockchain researchers have advanced these efforts through the development of other blockchain consensus methods, such as proof of stake (PoS) which also aim to achieve Byzantine fault tolerance.
How blockchain consensus protocols attain Byzantine fault tolerance
In any blockchain network, regardless of the consensus method used, miners or validators must reach consensus over the validity of each transaction before it’s added to the blockchain ledger. To check if a transaction is valid, it’s compared to the historical data on the ledger and discarded if it appears that the action will be inconsistent – for example, if someone is trying to send funds they don’t have in their account. However, validated transactions are included as a permanent, unalterable record on the ledger, which is shared with all participants. Therefore, all participants have shared points of truth against which to validate future incoming transactions.
Consensus protocols rely on the principle of game theory to provide sufficient incentives to network participants to act in the interests of the network rather than launch an attack. Large networks such as Bitcoin and Ethereum have remained secure for many years thanks to the incentive power of their reward structures.
Understanding Byzantine fault tolerance in blockchains
A Byzantine fault is defined as any distributed system failure that manifests with different symptoms to different observers. Since blockchain networks aim to achieve consensus regarding the state of the ledger, Byzantine faults typically take the form of conflicting information regarding transaction data, which may involve a miner or validator proposing an invalid block or attempting to validate an invalid transaction.
In some cases, the node operators behind such faults may be attempting to launch a malicious attack, but nodes can also suffer from faulty hardware or software that may cause them to inadvertently present false information. The larger a network becomes, the more likely such faults are to occur.
Therefore, the purpose of consensus protocols is not to eliminate such faults and achieve 100% Byzantine fault tolerance but to ensure that the system can continue operating regardless of the fact that Byzantine faults will inevitably occur. The consensus protocol only needs to ensure that a majority of nodes can reach a consensus while acting in the interests of the network, and the blockchain will continue operating with the transaction ledger intact.
Although Byzantine fault tolerance is a feature of blockchains, it’s also a feature of other types of distributed systems used in applications, including nuclear power plants, flight control systems, and space travel.
Byzantine fault tolerance essentials
Byzantine fault tolerance refers to the resilience of distributed systems against the failure of one or more components
Blockchains achieve Byzantine fault tolerance through the application of consensus protocols which enable network nodes to validate transactions
The objective of consensus protocols is not to eliminate Byzantine faults but to ensure that the system is sufficiently tolerant against faults, provided that a majority of participants are acting in its interests
The term takes its name from an allegory, the "Byzantine generals problem", developed to describe a situation in which, to avoid catastrophic failure of the system, the system's actors must agree on a concerted strategy, but some of these actors are unreliable.
is a measure of the ability of a distributed system to continue operating even if one or more of its components fails. Byzantine fault tolerance is a measure of the ability of a distributed system to continue operating even if one or more of its components fails.
Byzantine Fault Tolerance(BFT) is the feature of a distributed network to reach consensus(agreement on the same value) even when some of the nodes in the network fail to respond or respond with incorrect information.
Byzantine Fault Tolerance is a computer system's ability to continue operating even if some of its nodes fail or act maliciously. The term comes from a hypothetical called the Byzantine Generals Problem. This logical dilemma, as you'd expect, is about a group of Byzantine generals.
In distributed systems, Byzantine Fault Tolerance (BFT) is the characteristic of a distributed computer network to reach a sufficient consensus among majority nodes, regardless of the presence of a few malicious (Byzantine) nodes.
Practical Byzantine Fault Tolerance (PBFT) is a consensus mechanism designed to withstand Byzantine faults within a distributed network system. Originating from Leslie Lamport's conceptualization of the Byzantine Generals' Problem, PBFT was introduced by Miguel Castro and Barbara Liskov in 1999.
Byzantine fault tolerant protocols are algorithms that are robust to arbitrary types of failures in distributed algorithms. The Byzantine agreement protocol is an essential part of this task. The constant-time quantum version of the Byzantine protocol, is described below.
A Byzantine failure occurs when the system cannot tell faulty nodes and functioning nodes apart and thus, confuses valid and fraudulent transactions. To avoid failure, a majority of the nodes in a network must reach consensus.
Byzantine fault tolerance is 50% assuming zero network latency. It is around 46% (Ethereum) and 49.5% (Bitcoin) fault tolerant under actually observed conditions, but it goes down to 33% if network latency is equal to the block time and reduces to zero as network latency approaches infinity.
In other words, the pBFT consensus algorithm requires at least 3f+1 nodes in a system of f faulty nodes (byzantine nodes). Because as long as there are 3f+1 nodes, the majority of the non-faulty/honest nodes will always be able to reach a consensus no matter how the f faulty nodes interfere with the process.
Byzantine fault-tolerant broadcast is a fundamental problem in distributed computing. In Byzantine broadcast (BB) or Byzantine reliable broadcast (BRB), there is a designated broadcaster that sends its input value to all parties, and all non-faulty parties must deliver the same value.
The Byzantine generals problem is applicable in any distributed system where multiple parties need to agree on the state of the system and make decisions, and it illustrates the difficulties of achieving this consensus in a decentralized environment.
The objective of the BFT mechanism is to defend a network from a system failure. In the case of a peer-to-peer (P2P) network, such as a blockchain, transactions are deemed valid only if a group of nodes agrees it is.
Crash fault tolerance assumes that faulty nodes might fail by crashing, in which case they stop participating in the system while the rest of nodes continue to operate. Byzantine fault tolerance, on the other hand, allows for arbitrary fault behaviours, including malicious actions.
Mitigation. The objective of Byzantine fault tolerance is to be able to defend against failures of system components with or without symptoms that prevent other components of the system from reaching an agreement among themselves, where such an agreement is needed for the correct operation of the system.
Simplified Byzantine Fault Tolerance (SBFT): SBFT is a variant of PBFT that simplifies the message exchange process, reducing communication overhead while maintaining strong Byzantine fault tolerance guarantees.
Some of the Byzantine failures, such as omission failure, two-face attack, and crash failure, are particularly important to Blockchain and can cause inconsistency in Blockchain. For example, the Bitcoin network allows peers to join and leave freely.
The objective of Byzantine fault tolerance is to be able to defend against failures of system components with or without symptoms that prevent other components of the system from reaching an agreement among themselves, where such an agreement is needed for the correct operation of the system.
Delegated Byzantine Fault Tolerance (dBFT) is a consensus algorithm designed to provide high performance, high security, and fault tolerance in blockchain networks. It is based on the Byzantine Generals Problem, which aims to achieve a consensus in a distributed system despite the presence of faulty or malicious nodes.
The Byzantine generals problem is a well-known concept in distributed computing and computer science that describes the difficulty of coordinating the actions of several independent parties in a distributed system. Marshall Pease, Robert Shostak, and Leslie Lamport developed the idea in 1982.
Introduction: My name is Gregorio Kreiger, I am a tender, brainy, enthusiastic, combative, agreeable, gentle, gentle person who loves writing and wants to share my knowledge and understanding with you.
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