Saturday, January 12, 2013

The Circle is Completed

Sarah couldn’t wait and asked excitedly, “What did you find?” Rebekah added, “Did you find it?” Freyda simply said, “Patience!” as she spread her hands over the table. With this pause, Heinrich began, “There is a very special hiding place that is 11 bricks to the left and 6 bricks down from the bellows,” as his eyes panned each face, stopping at Rebekah’s, acknowledging her contribution with a nod. “It was a marvelous piece of engineering that father had done to conceal this,” as he put the bag forward and opened the drawstring that held it together. He had decided that he would bring the items out in the same order that he had found them, so he withdrew the cipher wheel and placed it on the table. Rebekah’s eyes lit up and she squealed with delight, “you found it!” But seeing it reminded her that it was her father who had this made and his hands touched it at one time. So she picked it up and held it in silence. “The circle is completed,” said Heinrich with understanding. She handed it to Sarah, who then inspected it, turned its inner wheel, and then tried to imagine how it was used. Freyda observed it in Sarah’s hands and then took her turn holding it, with the realization that her husband had used this for purposes that she was still trying to fathom. 

Freyda spoke rather rhetorically to Rebekah, “This must mean your father delivered the wheel to my husband, either in person, or via a courier. I’m sure that its use required some detailed instruction.” Rebekah responded, “Yes, unless your father already knew about things like this, he no doubt received help in using it. The wheel was invented by Leon Alberti in Italy about 60 years ago and my father learned of it through channels that I don’t fully understand.  The outer ring, with its uppercase alphabet, was used to spell the source text and the inner ring, with its lowercase alphabet, produced the text that is the real encoded message. The numbers in the outer ring are used with a codebook to know when to change the index value. So there is one more missing piece that we need.”

Heinrich suspected the small notebook was for that purpose, so he withdrew it immediately and said, “That’s what this must be.” Rebekah said, “may I see it?” Heinrich released it to her and she began looking at its pages. When she saw the tell-tale signs of codes and indices, she said, “yes, this is it; without this book, the wheel is just an interesting device. But, as I said before, all such documentation links the network together and should be destroyed.”

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