On Sat, Feb 19, 2000 at 10:12:20AM -0800, Spike Jones wrote:
> Please some of you information theorists, tell me if this is possible:
>
> Alpha and Charlie have a mutual friend Bravo, but do not know each
> other. All three have email, but have no website of their own. Suppose
>
> Alpha wants to know a piece of info about Charlie [something harmless,
> such as how many pets Charlie has] with the following stipulations:
>
> 0) Alpha does not wish to reveal his or her identity.
> 1) Charlie is willing to play the game, but wants to pass the info
> *only* to the unknown Alpha.
> 2) Bravo is helping both, allowing Alpha to pass questions or any
> other needed info to Charlie without revealing Alpha's identity. It
> is assumed that giving Charlie Alpha's email address reveals Alpha.
> 3) Charlie and Alpha are not required to borrow someone else's
> email address or website or involve a fourth person in any way.
> [Sending snail mail is an example of involving a fourth person.]
>
> Information scientists: is this theoretically possible to do? I suspect
>
> it is not, but I am unable to derive a proof. spike
>
A sends the question and A's public key to B. B forwards it to C.
C uses his private key and A's public key and the plaintext "3" to
generate his response. C sends B the message and C's public key to
B, who forward's them to A. A uses his private key and C's public
key to recover the text "3".
Does this qualify as a solution? All depends how you interpret
"wants to pass the info *only* to the unknown Alpha".
Only A has the info, it would seem to me.
Please restate the problem if it's not what you want.
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