This problem was introduced in the 80s by the mathematician Leslie Lamport. The problem goes like this: Khaleesi, John Snow, and Jorah Mormont has surrounded King's landing with their accompanied legions. Their goal is to conquer King's landing and behead Cercei. They are all positioned around King's landing. In order for them to be successful in breaching the gates and surviving the wildfire, they all must attack at the very same time.
An attack made simultaneously will result in victory, but if one of the legions does not attack, or if they attack at different times, the assault will likely fail. It is night time and the mother of dragons has decided that they shall attack at dawn. Now the problem of the Byzantine Generals problem asks the question: How can we, with 100% certainty, make sure that multiple entities, which are separated by distance, are in full agreement before an action is taken?
The distance between their legions are to wide apart to shout your plans. They could light signal fires to communicate their message, but then they risk exposing their plans to Cercei. The only reasonable option for them is to send messengers with their plans to each legion. But then Khaleesi would first have to send separate messages to John Snow and sir Jorah Mormont telling them to attack at dawn. But what happens if one of these messengers are killed before they can deliver the message?
John Snow and sir Jorah Mormont would then have to reply to this message, confirming that they are will be ready to attack at dawn. But what happens if the messenger they send back are killed before they can deliver the message?
Or what would happen if one of the messengers were captured by Cercei and replaced by some imposter?
Or even worse, what would happen for instance if Sir Jorah Mormont turned out to be a fucking liar, spying on our beloved queen? What happens if he says that he will attack at dawn but then decides to once again backstab Khaleesi?
How can we make sure that everyone is in agreement before an action is taken, and how can we make absolutely certain that we will always be in agreement, until the end of time? A system that is Byzantine Fault tolerant refers to a system which has solved the Byzantine Generals problem. A network like this has complete and continuous consensus between the nodes connected to the system at all times, and have identical records of what action is being taken, and previously has been taken. A cryptocurrency which is Byzantine fault tolerant is essentially a trust-engine.
It enables Khaleesi to remove the need for a third-party intermediary, like the Iron Bank of Braavos, to provide the trust that Khaleesi needs before she goes ballsdeep into King's landing with her dragons.
