20 lines
1 KiB
Text
20 lines
1 KiB
Text
The dining cryptographers' protocol is documented in Bruce Schneier's book
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as a kind of "cryptographic ouija board". It works as follows:
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A number of cryptographers are dining at a circular table. At the end of
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the meal, the waiter is summoned and asked for the bill. He replies,
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"Thank you, sir. The bill has been paid." The cryptographers now have the
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problem of working out whether someone at the table paid the bill, or
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whether the NSA has paid it as some sort of veiled threat. The protocol
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proceeds.
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Each cryptographer flips a coin, and shows the result ONLY to the
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participant on his RIGHT. Each cryptographer then compares his coin with
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that on his LEFT, and raises his hand if they show different faces. If any
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participant paid the bill, he "cheats" and does the opposite, that is, he
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raises his hand if the coins show the same face. Now, the hands are
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counted. An odd number means that someone at the table paid the bill. An
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even number means that the NSA paid.
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WWW: http://search.cpan.org/dist/Crypt-Dining
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Author: Shevek <shevek@cpan.org>
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