# How to send the valuable object

rgoudie
Posers and Puzzles 29 Jul '04 18:31
1. 29 Jul '04 18:31
You want to send a valuable object to a friend. You have a box which is more than large enough to contain the object. You have several locks with keys. The box has a locking ring which is more than large enough to have a lock attached. But your friend does not have the key to any lock that you have. Note that you cannot send a key in an unlocked box, since it might be copied. How would it possible to send the object?

-Ray.
2. Cribs
Moderately Offensive
29 Jul '04 22:161 edit
Originally posted by rgoudie
You want to send a valuable object to a friend. You have a box which is more than large enough to contain the object. You have several locks with keys. The box has a locking ring which is more than large enough to have a lock attached. But ...[text shortened]... ht be copied. How would it possible to send the object?

-Ray.
May I assume that my friend is also equipped with a box,
and his own set of keys and locks?

Dr. Cribs
3. 30 Jul '04 00:191 edit
Originally posted by Cribs
May I assume that my friend is also equipped with a box,
and his own set of keys and locks?

Dr. Cribs
I'll reveal this much:
Your friend does not need another box.
Your friend may very well possess another lock with keys.

I'll further add that the priority here is to send the object securely over and above any other consideration.

-Ray.
4. Cribs
Moderately Offensive
30 Jul '04 00:261 edit
Originally posted by rgoudie
I'll reveal this much:
need another box.
Your friend may very well possess another lock with keys.

-Ray.
[/b]
Pretty Good Privacy is based on the solution to this problem then.

Does that suffice as an answer, of shall I explain further?

Dr. Cribs
5. 30 Jul '04 00:27
Originally posted by Cribs
Pretty Good Privacy is based on the solution to this problem then.
The concept is similar. ðŸ˜€

-Ray.
6. Cribs
Moderately Offensive
30 Jul '04 00:29
Originally posted by rgoudie
The concept is similar. ðŸ˜€

-Ray.
You don't have a solution based on the friend not having
his own locks and keys, do you? I'm sure the computer
security world would love to know it, if you did.

Dr. Cribs
7. 30 Jul '04 00:34
Originally posted by Cribs
You don't have a solution based on the friend not having
his own locks and keys, do you? I'm sure the computer
security world would love to know it, if you did.

Dr. Cribs
This is technically another clue. ðŸ™‚

The solution does not involve the friend not having their own lock and key.

-Ray.
8. Cribs
Moderately Offensive
30 Jul '04 00:452 edits
Originally posted by rgoudie
This is technically another clue. ðŸ™‚

The solution does not involve the friend not having their own lock and key.

-Ray.
EDIT: Scratch all that nonsense. I didn't notice the
9. 30 Jul '04 01:07
Originally posted by Cribs
EDIT: Scratch all that nonsense. I didn't notice the
Come on, Cribs, I know you can do it. A pimp gotta keep his mind sharp if he's gonna keep track of his bizness.

Here's a recap of the criteria:

He wants to send the object securely, which means that the box must have a lock on it.
He has at least one lock and key, but the recipient does not possess a key for the lock.
The recipient does possess their own lock and key.

Anything else goes. How does he get the object to the recipient securely? You may have to get lateral on this puzzle.

-Ray.
10. Cribs
Moderately Offensive
30 Jul '04 01:251 edit
Originally posted by rgoudie
Come on, Cribs, I know you can do it. A pimp gotta keep his mind sharp if he's gonna keep track of his bizness.

Here's a recap of the criteria:

He wants to send the object securely, which means that the box must have a lock on it. ...[text shortened]... securely? You may have to get lateral on this puzzle.

-Ray.
because I thought you said it could be done without the friend
having his own lock/key pair. I explained why that was impossible,
and then noticed that I misread what you wrote.

So, I do know the solution, but I won't detail it here
until others take a swing at it, because it is a pretty
interesting problem.

Dr. Cribs
11. bbarr
Chief Justice
30 Jul '04 05:04
Have your friend send you his lock. Have your friend keep the key to this lock. Use this lock to lock the box you want to send. Send the box to your friend.
12. 30 Jul '04 13:351 edit
Originally posted by bbarr
Have your friend send you his lock. Have your friend keep the key to this lock. Use this lock to lock the box you want to send. Send the box to your friend.
I must admit this as a plausible solution, but not the particular solution that I am looking for, How about if I add these two extra constraints:

No lock may be sent unless it is properly locked shut.
No keys may be sent at all at any time.

-Ray.
13. Cribs
Moderately Offensive
30 Jul '04 14:211 edit
Originally posted by rgoudie
I must admit this as a plausible solution, but not the particular solution that I am looking for, How about if I add these two extra constraints:

No lock may be sent unless it is properly locked shut.
No keys may be sent at all at any time.

-Ray.
These constraints together with your original ones make this
problem impossible.

Bbarr's solution is what I had in mind. That is the essence
of public key encryption, which is more or less the state of
the art in electronic security. If your newly stated problem
had a solution, it would be a major breakthrough in that field
and you could earn untold fortunes on it. But it doesn't,
unless you have stated it wrong, or unless I am misunderstanding it.

Your first new constraint is the killer. Any new security methods based
on keys always must address the &quot;key distribution problem,&quot; and
an open lock is essentially analogous to a &quot;public key&quot;.

Dr. Cribs
14. 30 Jul '04 14:231 edit
Originally posted by Cribs
These constraints together with your original ones make this
problem impossible.

Bbarr's solution is what I had in mind. That is the essence
of public key encryption, which is more or less the state of
the art in electronic security. ...[text shortened]... stated it wrong, or unless I am misunderstanding it.

Dr. Cribs
The solution is straightforward if you think outside the box (pun unintended).

-Ray.
15. Cribs
Moderately Offensive
30 Jul '04 14:261 edit
Originally posted by rgoudie
The solution is straightforward if you think outside the box (pun unintended).

-Ray.
Well, there is the degenerate solution that you just
physically hand the valuable item to your friend.

That meets all of the constraints, unless your notion
of &quot;send&quot; disallows this. If that is that case then you
should also not be able to physically hand over locks
and keys, and I maintain that your new problem has
no solution.

Dr. Cribs