20131029, 19:13  #12 
If I May
"Chris Halsall"
Sep 2002
Barbados
3·29·109 Posts 

20131029, 20:23  #13 
∂^{2}ω=0
Sep 2002
República de California
2D60_{16} Posts 
I took the OP note "Eve is sitting at Alice's restaurant table" as being important  if we were talking about bulk electroniccomms encryption, there would be little point in starting a new thread in Puzzles about that, would there?
So I am going with the howcanAandBexchangeaPINunderC'snose scenario, which supposes that C hears everything that is said by A and B. Couple possible prearranged simplecrypto schemes: o Alice conveys PIN via numbersipsfromwineglass  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]. 
20131029, 20:28  #14  
If I May
"Chris Halsall"
Sep 2002
Barbados
3·29·109 Posts 
Quote:


20131029, 20:44  #15 
∂^{2}ω=0
Sep 2002
República de California
2^{5}·3·11^{2} Posts 

20131029, 20:49  #16 
If I May
"Chris Halsall"
Sep 2002
Barbados
3·29·109 Posts 

20131029, 21:18  #17 
If I May
"Chris Halsall"
Sep 2002
Barbados
3×29×109 Posts 
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.... 
20131030, 03:03  #18 
Jun 2003
4,861 Posts 

20131030, 05:24  #19 
May 2013
East. Always East.
3277_{8} Posts 

20131030, 05:28  #20 
May 2013
East. Always East.
11×157 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. 
20131030, 10:16  #21 
I quite division it
"Chris"
Feb 2005
England
4035_{8} 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.) 
20131030, 11:43  #22 
Undefined
"The unspeakable one"
Jun 2006
My evil lair
5·1,217 Posts 

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