Person ‘A’ wants to send a secret message to his friend ‘B’ through a mail, but 'C' (A’s friend), whom 'A' does not trust has access to all A’s mails. So 'A' puts his message in a box with a lock but 'A' is not allowed to send a key. How can 'A' send his message through securely?
I think it would take a bit of back and forth but I have a solution to this.
A will lock the box and send it to B. B will lock another lock on to it of which he has the key and sends it back to A. A will remove his lock and send it back to B. Now B can read it by unlocking his lock with his key.
This process reverses if B has to send a message to A and vice versa.
Send the box without the lock to B.
B can’t open it, but can put another lock on the box.
B sends this box with the 2 locks back to A, A unlock his lock and send it back to B again.
So there is just B’s lock on the box and B can now open it.
A King wants to send the diamond ring to his girlfriend securely. He got multiple locks and their corresponding keys. His girlfriend does not have any keys to these locks and if he sends the key without a lock, the key can be copied in the way. How can King send the ring to his girlfriend securely?
John wants to send a letter to Peter, who lives on Tesla Street. John doesn't remember the house number. However, he knows that it has 4 digits, it is a multiple of 5 and 7 and that the last digit is 0. What is the minimum number of letters that John has to send to be sure that Peter receives his letter?
Tom wants to send Sally an expensive ring through the mail because they live thousands of kms apart. The only problem is that everything sent through the mail is stolen unless there is a lock put on it. Both Tom and Sally have plenty of locks and keys but they don't have any of the same locks or keys.
How can Tom send Sally the ring without it getting stolen?
A spy sends an encoded message to the police officer and challenges him.
He says “If you can crack this, you are smarter than me”
The coded message is: YYURYYUBICURYY4ME
What message did the spy send?
