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This is the first of our challenge ciphers.
We recommend that you attempt them in order, as the solution of each challenge gives a small (and necessary!) hint for the next challenge.
An example of a simple Public Key code, called the Knapsack Code is described in this article, alongside some information on its origins. A knowledge of modular arithmetic is useful.
Can you crack these very difficult challenge ciphers? How might you systematise the cracking of unknown ciphers?