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StuartNolan Elite user 479 Posts |
I came across this conundrum the other day. I don't know the answer but though you folk might enjoy puzzling over it.
http://blog.jgc.org/2011/08/security-con......and.html From reading the book here is a little more context. The conundrum is this. Pandarus was sent into Belgium to recruit and train new agents, He had to give them security checks so that when they started seniding morse messages to SOE, then SOE would know that this was a genuine agent recruited by Pandarus and not an imposter. The weakness of Pandarus knowing the security checks that he gave to recruits is that, if he were caught, he could blow the security of the whole circuit and all the messages sent by any agent in it, if he had the checks tortured out of him by the Gestapo. The clever trick that Marks came up with enabled Pandarus to give security checks to new agents, which would be known to SOE back in London, but NOT possible for Pandarus to remember even involuntarily under torture. That's the riddle. How did Pandarus hand checks to new agents, NOT in writing, in a form that was known to SOE, memorable to the new agent, but not memorisable by him either voluntarily or involuntarily? Bear in mind also that a security check cannot be a simple word or name, since it's appearance in every message would give it away very quickly. Sometimes they were things like 'make a spelling error in every sixth word' or 'place three dummy letters at the beginning and end of the message'. The point of these is that, if the checks were omitted from the message, it would be known that the agent was captured. The Nazis would not be able to guess the security checks, so would either have to deduce them from past traffic if they had monitored it, or torture it out of the agent. If they did so, they would be able to continue the agent's traffic but under their own control. Very bad news for SOE and the war, obviously. Happened to the entire Dutch network - all captured and the Germans manning their wireless sets and pretending to be them, while gleaning information and supplies over quite a long period. S
"One should always be a little improbable." - Oscar Wilde
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TomasB Inner circle Sweden 1144 Posts |
Your last phrase seem to indicate that the security check is done in a message sent by the agent. That is not mentioned in the link you provided. Is it possible that the actual check later involves the SOE sending something to the agent, to await his reaction to what was just sent? If it's the correct reaction (maybe the experiment is repeated a few times for statistics) it is plausable that it's the correct agent replying.
It reminds me a bit about proving to someone that you have a solution to a problem, but not showing them how a solution is reached. It's done by first mapping the problem in some random way and then show the solution to the mapping. However, the person flips a coin each time to decide if he should see the mapping or the solution. This is repeated with different mappings with a coin toss each time, until he is very sure that you actually have a solution. A small reservation that I might have described that totally wrong. /Tomas |
landmark Inner circle within a triangle 5194 Posts |
Quote:
It reminds me a bit about proving to someone that you have a solution to a problem, but not showing them how a solution is reached. It's done by first mapping the problem in some random way and then show the solution to the mapping. However, the person flips a coin each time to decide if he should see the mapping or the solution. This is repeated with different mappings with a coin toss each time, until he is very sure that you actually have a solution. This sounds interesting, Tomas. Could you describe this a little more as to what you mean? An example maybe? Thanks,
Click here to get Gerald Deutsch's Perverse Magic: The First Sixteen Years
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TomasB Inner circle Sweden 1144 Posts |
It's called Zero Knowledge Proof, and I vaguely remember the example I saw many years ago being about proving to someone that you had colored someone's map with the 4-color theorem, while not actually showing how you had colored it.
I found this example on how to prove that you have solved a Sudoku without showing your solution: http://www.drdobbs.com/architecture-and-......32300619 Once I found that it's called Zero Knowledge Proof, it of course became easier to find lots of examples: http://en.wikipedia.org/wiki/Zero-knowledge_proof Some clever stuff! /Tomas |
landmark Inner circle within a triangle 5194 Posts |
Very interesting indeed. Thanks very much Tomas.
Click here to get Gerald Deutsch's Perverse Magic: The First Sixteen Years
All proceeds to Open Heart Magic charity. |
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