A Byzantine error is any error that presents different symptoms to different observers.  A Byzantine failure is the loss of a system service due to a Byzantine error in systems that require consensus.  A Byzantine error (even the interactive coherence, the congruence of the sources, the avalanche of errors, the problem of the Byzantine agreement, the problem of Byzantine genetics and Byzantine failure) is a condition of a computer system, especially distributed computer systems, where components can fail and contain imperfect information about the failure of a component. The term has its name from an allegory, the “Bizantin General`s problem”, designed to describe a situation in which the players in the system must agree on a concerted strategy to avoid a catastrophic failure of the system, but some of these actors are unreliable. The problem of reaching a Byzantine consensus was conceived and formalized by Robert Shostak, who called it a problem of interactive coherence. This work was done in 1978 as part of the NASA-sponsored SIFT project at the Computer Science Lab at SRI International. Sift (for Software Implemented Fault Tolerance) was the child of John Wensley`s brain and was based on the idea of using several versatile computers that would communicate in pairs of messages to reach consensus, even if some of these computers were defective. The objective of the Byzantine margin of error is to protect against system component failures, with or without symptoms, preventing other components of the system from reaching an agreement if such an agreement is necessary for the system to function properly. Some astronaut flight systems such as SpaceX`s Dragon look at the Byzantine margin of error in their design. The Byzantine margin of error can be reached if loyal (non-defective) generals have a majority agreement on their strategy. It is possible to indicate a default voting value for missing messages. For example, missing messages may .
If the agreement is that the votes are in the majority, a standard strategy pre. B assigned can be used.  At the beginning of the project, it was not known how many computers were needed to ensure that a conspiracy of defective computers could not “counteract” the efforts of computers that function properly to reach consensus. Shostak has shown that it takes at least 3n-1 and has developed a two-round 3n-1 messaging protocol that would work for No. 1.