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The Substitution Cipher > The Substitution Cipher - Pg. 37

A Cryptography Primer 37 When the Enigma was in use, with each subsequent key press, the rotors would change in alignment from their set positions in such a way that a different letter was produced each time. The operator, with a message in hand, would enter each character into the machine by pressing a typewriter-like key. The rotors would align, and a letter would then illuminate, telling the operator what the letter really was. Likewise, when enciphering, the operator would press the key and the illuminated letter would be the cipher text. The continually changing internal flow of electricity that caused the rotors to change was not random, but it did create a polyalphabetic cipher that could be different each time it was used. 3. Ciphers Cryptography is built on one overarching premise: the need for a cipher that can reliably, and portably, be used to encrypt text so that, through any means of cryptanalysis--differential, deductive, algebraic, or the like--the ciphertext cannot be undone with any available technology. Throughout the centuries, there have been many attempts to create simple ciphers that can achieve this goal. With the exception of the One Time Pad, which is not particularly portable, success has been limited. Let's look at a few of these methods now.