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| • |
Suppose the
sender is also trying to communicate
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another message
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The
other message is completely independent.
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It
looks like a random bit stream.
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Whenever the
sender has to choose between two
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equally good
ways of encoding the data, he uses a bit
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from the other
message to make the decision
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After the
receiver has losslessly reconstructed the
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original data,
the receiver can pretend to be the sender.
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This
enables the receiver to figure out the random bit
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in
the other message.
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So the original
message cost one bit less than we
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thought because
we also communicated a bit from
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another message.
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