Confidential mail puzzle
X wants to send a Confidential message to his friend Y in the mail.
But Z (X’s Friend), who X don’t trust, has access to all X’s mail. So X put his message in a box with a lock. But X is not allowed to send a key!
How can X send his message through securely?
Assuming that the box has provision to support at least two locks at a time AND that delay in receiving the letter is not a matter of concern:
Use the ‘double lock’ method. ‘X’ should lock the box and send it to Y (X keeps the key with himself). Y, in turn, should add another lock on the box and send it back (key remains with Y). On receipt of the box, X should open and remove his lock and send it back to Y (with the other lock intact.) Once the box is received, Y can open the box and retrieve the letter by opening his own lock.
More puzzles to try-
- 3 + 3 = 3 5 + 4 = 4 1 + 0 = 3 2 + 3 = 4 ...Read More »
- Which letter replaces the question markRead More »
- There is a building of 100 floors -If an egg drops from the Nth floor or above it will break. ...Read More »
- Five puzzleFry ship’s pirates have obtained 100 gold coins and have to divide up the loot. The pirates are all ...Read More »
- There are 10 stacks of 10 coins each. Each coin weights 10 gms. However, one stack of coins is defective ...Read More »
- Dr.Willam wants to operate for three different persons who were wounded. But he had only two surgical gloves. There is ...Read More »
- Which clock works best? The one that loses a minute a day or the one that doesn’t work at all?Read More »
- In the gear arrangement, To which one will the needle touch, 1 OR 2Read More »
- A man leaves his house in the morning to go to office and kisses his wife. In the evening on ...Read More »
- A murderer is condemned to death. He has to choose between three rooms. The first is full of raging fires, ...Read More »
- Paul, Sam and Dean are assigned the task of figuring out two numbers. They get the following information: Both numbers ...Read More »
- A bridge will collapse in 17 minutes. 4 people want to cross it before it will collapse. It is a ...Read More »
- In a country where everyone wants a boy, each family continues having babies till they have a boy. After some ...Read More »
- A devotee goes to three temples, temple1, temple2 and temple3 one after the other. In front of each temple, there ...Read More »
- There is a perfectly accurate analog watch with hour, minute, and second hands. How many times a day do all three ...Read More »
- Four days are there which start with the letter ‘T‘. I can remember only two of them as “Tuesday , Thursday”. ...Read More »
- Two fathers took their sons to a fruit stall. Each man and son bought an apple, But when they returned ...Read More »
- A farmer is taking her eggs to the market in a cart, but she hits a pothole, which knocks over ...Read More »
- Let it be simple and as direct as possible. Interviewer : Tell me how much time (in days) and money would ...Read More »
- In the middle of the confounded desert, there is the lost city of “Ash”. To reach it, you will have ...Read More »