Box and Locks


You want to send a valuable object to a friend. You have a box to contain the object. The box has a locking ring which is more than large enough to have a lock attached. You and your friend have several locks with keys. But your friend does not have the key to any lock that you have, and vice versa. How do you do it? Note that you cannot send a key in an unlocked box, since it might be copied.

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Do you know what Mesothelioma is?


Attach a lock to the ring. Send it to her. She attaches her own lock and sends it back. You remove your lock and send it back to her. She removes her lock.


Ankit Goswami said...

Put the object into the box, lock it with one of your locks, and send the box to your friend. Your friend now locks it with one of his own locks and returns it. When you receive it this time, remove your lock and send it back. Now your friend can unlock his own lock and get the object.

shiba shankar said...

suppose:: you have= X_lock & X_key
you friend has= Y_lock & Y_key

you send the box with X_lock >>>> to ur friend..
Now ur friend send with Y_lock >>>> to u..

Now box have= 2 locks X & Y

u can unlock the X_lock, then send it to ur friend with Y_lock.

Now ur friend has Y_key ..So he can unlock & get the OBJECT.

prashant said...
This comment has been removed by the author.
Anonymous said...

Can't you just put one of those locks with the 3 digit codes on it, and when your friend gets the box, they call you up and ask for the code...??