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Posers and Puzzles

Posers and Puzzles

  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. Standard member Cribs
    Moderately Offensive
    29 Jul '04 22:16 / 1 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 00:19 / 1 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. Standard member Cribs
    Moderately Offensive
    30 Jul '04 00:26 / 1 edit
    Originally posted by rgoudie
    I'll reveal this much:
    Your friend does [b]not
    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.

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

    -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.

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

    -Ray.
  8. Standard member Cribs
    Moderately Offensive
    30 Jul '04 00:45 / 2 edits
    Originally posted by rgoudie
    This is technically another clue.

    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
    double negative in your sentence.
  9. 30 Jul '04 01:07
    Originally posted by Cribs
    EDIT: Scratch all that nonsense. I didn't notice the
    double negative in your sentence.
    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. Standard member Cribs
    Moderately Offensive
    30 Jul '04 01:25 / 1 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.
    PGP's foundation is the answer. I tried replying to your clue, after I misread it,
    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. Donation 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 13:35 / 1 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. Standard member Cribs
    Moderately Offensive
    30 Jul '04 14:21 / 1 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 "key distribution problem," and
    your problem specifically disallows this aspect to be addressed, since
    an open lock is essentially analogous to a "public key".

    Dr. Cribs
  14. 30 Jul '04 14:23 / 1 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. Standard member Cribs
    Moderately Offensive
    30 Jul '04 14:26 / 1 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 "send" 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