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2013-10-29, 19:13   #12
chalsall
If I May

"Chris Halsall"
Sep 2002

2·3·1,499 Posts

Quote:
 Originally Posted by Mini-Geek As long as Eve can only hear Alice's side of the conversation, the encryption works.
But let us assume you can't guarantee that...

Remember that book we both read so many years ago?

496.297.

 2013-10-29, 20:23 #13 ewmayer ∂2ω=0     Sep 2002 República de California 3×612 Posts I took the OP note "Eve is sitting at Alice's restaurant table" as being important - if we were talking about bulk electronic-comms encryption, there would be little point in starting a new thread in Puzzles about that, would there? So I am going with the how-can-A-and-B-exchange-a-PIN-under-C's-nose scenario, which supposes that C hears everything that is said by A and B. Couple possible prearranged simple-crypto schemes: o Alice conveys PIN via number-sips-from-wineglass - wipe rim or sip water to end current digits. o Alice stealthily uses foot to squeeze Bob's junk under table, Flashdance style - number of squeezes conveys data, kick Bob's shin with other foot to end current digit. [Bob is glad that PIN is only 4 digits long].
2013-10-29, 20:28   #14
chalsall
If I May

"Chris Halsall"
Sep 2002

100011001000102 Posts

Quote:
 Originally Posted by ewmayer Couple possible prearranged simple-crypto schemes: o Alice conveys PIN via number-sips-from-wineglass - wipe rim or sip water to end current digits. o Alice stealthily uses foot to squeeze Bob's junk under table, Flashdance style - number of squeezes conveys data, kick Bob's shin with other foot to end current digit. [Bob is glad that PIN is only 4 digits long].
That's not crypto. That's simple out-of-band communications. Easily caught with current AI.

2013-10-29, 20:44   #15
ewmayer
2ω=0

Sep 2002
República de California

1116310 Posts

Quote:
 Originally Posted by chalsall That's not crypto. That's simple out-of-band communications. Easily caught with current AI.

2013-10-29, 20:49   #16
chalsall
If I May

"Chris Halsall"
Sep 2002

2·3·1,499 Posts

Quote:
 Originally Posted by ewmayer Only if the AI has access to Bob's junk.
Don't we all?

2013-10-29, 21:18   #17
chalsall
If I May

"Chris Halsall"
Sep 2002

2×3×1,499 Posts

Quote:
 Originally Posted by chalsall Don't we all?
In my opinion, we find ourselves in a very interesting situation, and very interesting times...

Some people are trying to disrupt and discredit our community.

Some people make sense, other's don't.

I don't fully understand the motives.

Deep thought is welcome....

2013-10-30, 03:03   #18
axn

Jun 2003

107618 Posts

Quote:
 Originally Posted by ewmayer I took the OP note "Eve is sitting at Alice's restaurant table" as being important
Quote:
 Originally Posted by Flatlander So Alice is on the phone to Bob
My bolding.

2013-10-30, 05:24   #19
TheMawn

May 2013
East. Always East.

11×157 Posts

Quote:
 Originally Posted by ewmayer [Bob is glad that PIN is only 4 digits long].
But Bob wishes that her pin was all nines.

 2013-10-30, 05:28 #20 TheMawn     May 2013 East. Always East. 172710 Posts If Alice cannot hear Bob then Bob can just offer some kind of code that Alice does not know and it is impossible for her to have the slightest clue what the answer is. How much must I subtract from 37 to get the first digit? How much must I subtract from 11 to get the second digit? Etc. He chooses the numbers. When EVE says 35, 3, 7 560 and 0, how can Alice have ANY clue? On the other hand, if Alice hears both Eve and Bob then there is no way for them to devise a code.
 2013-10-30, 10:16 #21 Flatlander I quite division it     "Chris" Feb 2005 England 31·67 Posts Solved with MOD 10 then; but just before Bob needs the PIN Alice and Bob are struck down with Stupiditis and are only able to comprehend integers 0 through 9, ... (Or some other restriction to make it more interesting.)
2013-10-30, 11:43   #22
retina
Undefined

"The unspeakable one"
Jun 2006
My evil lair

2×3×907 Posts

Quote:
 Originally Posted by Flatlander ... struck down with Stupiditis ...
I know how that feels. I get struck be that very frequently. As for solving this new modified puzzle I feel an attack of Stupiditis coming on now. :(

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