Cryptography
...to sophisticated mathematical techniques. No matter what the form however, there are some underlying things that must be done encrypt the message and decrypt the encoded message.
One of the earliest and simplest methods ever used to encrypt and decrypt messages is called the Caesar cipher method, used by Julius Caesar during the Gallic war. According to this method, letters of the alphabet are shifted by three, wrapping around at the end of the alphabet. For example,
PlainTest: a b c d e f g h i j k l m n o p q r s t u v w x y z
Caesar shift: d e f g h I j k l m n o p q r s t u v w x y z a b c
When encrypting a message, you take each letter of the message and replace it with its corresponding letter from the shifted alphabet. To decrypt an encoded message, you simply reverse the operation. That is, you take the letter from the shifted alphabet and replace it with the corresponding letter from the plaintext alphabet. Thus the string the quick brown fox becomes wkh txlfn eurzq ira
Another type of cipher is known as Transposition cipher. In this type of cipher, letters in the original message are re-arranged in some methodical way for instance, reverse the letters in each string. Thus the string the quick brown fox becomes eht kciuq nworb xof
Still yet another cipher method is the Reverser cipher. This method does not only reverses the letters in each word, but as does the Transposition cipher, but it also reverses the result generated from the Transposition cipher. Hence the original message the quick brown fox becomes xof nworb kciuq eht
Class design
All three methods Caesar, Transposition and Reverser - have something in common. They encrypt and decrypt messages. That is, they take a string of words and translate each word using the encoding algorithm appropriate for that cipher. Thus each class cipher will need polymorphic...
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