Two generals problem
Imagine you and your friend are two generals planning to attack an enemy castle. You both know that in order to successfully attack, you need to coordinate your movements. However, there is a problem – you are far away from each other and cannot directly communicate because the enemy may intercept your messages.
Now, you want to send a message to your friend to let them know if they should attack or retreat, and they also want to do the same with you. But since you cannot talk directly, you need to send messengers.
Since the enemy could potentially intercept your messengers, there is a chance they may alter or block the messages. This means that even if you send a messenger to your friend saying "attack," the enemy could change the message to "retreat" before it reaches your friend.
To make matters even more complicated, there is a chance that the messenger may get lost or killed by the enemy while delivering the message. This means that even if you send a messenger saying "attack," your friend may never receive the message and not know what to do.
The problem you and your friend face is how can you both agree on whether to attack or retreat without being able to communicate directly and knowing that your messages may be changed or never delivered.
Many smart people have tried to solve this problem, but it turns out there is no perfect solution. However, there is a strategy called "the Two Generals Problem" that can help you minimize the chances of communication failure.
The strategy works like this: you agree with your friend in advance on a specific number of messengers to send. You also agree that if a messenger is killed or the message is changed, you will wait for a specific amount of time before deciding what to do.
For example, you both agree to send five messengers. You tell your friend that if they receive at least three messengers saying "attack," they should attack. If they receive at least three messengers saying "retreat," they should retreat. But if they receive any other combination, they should wait for 10 minutes and then make a decision.
Your friend agrees to the same plan and sends five messengers to you. If you receive at least three messengers saying "attack," you attack. If you receive at least three messengers saying "retreat," you retreat. But if you receive any other combination, you wait for 10 minutes and then make a decision.
By using this strategy, you and your friend increase the chances of communicating your intentions accurately. Even if some messengers get lost or their messages are changed, as long as you both receive enough correct messages, you can make a decision together.
However, it's important to remember that there is still a small chance that things could go wrong. For example, if the enemy intercepts all the messengers and changes their messages, you may never reach a decision. That's why the Two Generals Problem remains a challenging puzzle that people continue to study and try to find better solutions for.
Now, you want to send a message to your friend to let them know if they should attack or retreat, and they also want to do the same with you. But since you cannot talk directly, you need to send messengers.
Since the enemy could potentially intercept your messengers, there is a chance they may alter or block the messages. This means that even if you send a messenger to your friend saying "attack," the enemy could change the message to "retreat" before it reaches your friend.
To make matters even more complicated, there is a chance that the messenger may get lost or killed by the enemy while delivering the message. This means that even if you send a messenger saying "attack," your friend may never receive the message and not know what to do.
The problem you and your friend face is how can you both agree on whether to attack or retreat without being able to communicate directly and knowing that your messages may be changed or never delivered.
Many smart people have tried to solve this problem, but it turns out there is no perfect solution. However, there is a strategy called "the Two Generals Problem" that can help you minimize the chances of communication failure.
The strategy works like this: you agree with your friend in advance on a specific number of messengers to send. You also agree that if a messenger is killed or the message is changed, you will wait for a specific amount of time before deciding what to do.
For example, you both agree to send five messengers. You tell your friend that if they receive at least three messengers saying "attack," they should attack. If they receive at least three messengers saying "retreat," they should retreat. But if they receive any other combination, they should wait for 10 minutes and then make a decision.
Your friend agrees to the same plan and sends five messengers to you. If you receive at least three messengers saying "attack," you attack. If you receive at least three messengers saying "retreat," you retreat. But if you receive any other combination, you wait for 10 minutes and then make a decision.
By using this strategy, you and your friend increase the chances of communicating your intentions accurately. Even if some messengers get lost or their messages are changed, as long as you both receive enough correct messages, you can make a decision together.
However, it's important to remember that there is still a small chance that things could go wrong. For example, if the enemy intercepts all the messengers and changes their messages, you may never reach a decision. That's why the Two Generals Problem remains a challenging puzzle that people continue to study and try to find better solutions for.