Can you solve the hat riddle?

Ajouté : 2026-05-26

[00:00:00]Here's the problem. You and three amigos are buried neck deep in sand in a prison yard facing a life sentence. The guards offer you a deal. Guess your hat color and you all go free. There are two black hats and two white hats. Three of you are in a line facing a wall and the fourth is on the other side of the wall.

[00:00:14]Each of you can only see the hats of the people buried in front of you. A minute passes in silence and suddenly one of you shouts out the correct answer and it's not a guess. You guys all go free.

[00:00:23]So, which one of you was it and how did you know? Pause right now. I think you guys can figure it out. I'll give you the right answer in three, two, one. It was prisoner B who got the right call. See, prisoner B realized that if B and C were wearing the same color, well then prisoner A should have shouted out the answer straight away. But because person A stayed silent, B knew that he and C must be wearing different colors.

[00:00:44]Since B can see that C is wearing white, he knows that his own hat must be black.

[00:00:48]This is one of those strange cases where [music] silence carries information.

[00:00:51]Hackers actually use a similar technique to steal passwords. If a server rejects a wrong password in 1 millisecond, but then they change the first letter on their next attempt and now it takes 1.2 milliseconds, that suggests that the first letter was correct. That's because some servers check each character one by one, comparing them with the stored passwords. So, the longer the delay, the more correct characters. So, hackers build on this to get each letter of the password.