4 Caesarean cipher
Caesar wrote, “Gallia est omnis divisa in partes tres.” If he had wanted the message to be a secret, he would have written, “Tnyyvn rfg bzavf qvivfn va cnegrf gerf.” This subtle encryption was easy to concoct, yet even a literate spy would be unable to translate the scrambled Latin without knowing the key. On the receiving end, where the deciphering method is known, the message is quickly decoded and . . . pity poor Gaul. This method of encoding is today known as the Caesarean cipher.
The Caesarean cipher is by no means secure, but it’s a fun programming exercise. It also opens the door to the concepts of filters and filter programming in C. This chapter covers the concept of a filter, including stuff like this:
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Dealing with ...
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