Cryptography

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Cryptography

Cryptography is the science of preparing communication intended to be intelligible only to the person possessing the key or method of developing the hidden meaning by cryptoanalysis using apparently incoherent text (Encarta Encyclopedia). The movie mercury rising is a good example of cryptography. It’s about a little boy who is autistic. The little boy can do puzzles such as cryptography easily. One day while on the computer the boy cracks a highly secretive government code. The governmental agency wants the young boy found and killed for cracking the code it took years to write.

Cryptography started a long, long time ago with Julius Caesar. When he wanted only his people to know something he used cryptography. He did this by replacing A’s with D’s, B’s with E’s, and so on down the alphabet. This was known as "shift by 3", for obvious reasons. The Jewish writers also used a code of their own called Atbash. They did it by reversing the alphabet, they used the last letter of the alphabet in place of the first, the next to last for the second, and so on. Atbash is exemplified in the Bible,

Jeremiah 25:25, where "Sheshech" is written for Babel (Babylon). As you can see, cryptography has been used for many years and is continuing to become more high tech.

The term cryptography is sometimes restricted to the use of ciphers, that is, to methods of transposing the letters of plain text (unencrypted) messages, or to methods involving the substitution of other letters or symbols for the original letters of a message. And to various combinations of such methods, all according to prearranged systems. Ciphers of various types have been and can be devised. All of them fall into to one of two categories, transposition and substitution. In transportation ciphers, the message is usually written, without word divisions. They are rows of letters arranged in a rectangular block. The letters are then transposed in a prearranged order such as by vertical columns, diagonals, or spirals.

There are two types of ciphers, simple and complex. In a simple substitution cipher is particular letter or symbol is substituted for each. In a multiple substitution (polyalphabetic) ciphers, a keyword of number is employed. And in more complicated polyalphabetic systems, the letters of the keyword may tell which of a series of mixed substitution alphabets is to be used to encipher each letter of the message.

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