The inner disc could be turned, resulting in different cipher letters matching up with the true alphabet in a predetermined manner.
In 1902 Redl became a spy for Russia, and for the next 11 years he gave the Russians codes, ciphers, letters, maps, photographs, army orders, mobilization plans, and reports on the conditions of roads and railways within Austria.
The story involves cryptography with a detailed description of a method for solving a simple substitution cipher using letter frequencies.
The radio waves created each time a key is struck on the keyboard of a teletypewriter or an electrical cipher machine differ from letter to letter.
Basically, a substitution cipher involves substituting one letter for another letter, according to some predetermined rule.
Take, for example, the following: in a monoalphabetic substitution cipher (in which each letter is simply replaced by another letter), the frequency with which letters occur in the plaintext alphabet and in the ciphertext alphabet is identical.
It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet.
In some communications with Beauregard, Johnston used the Caesar Cipher, in which each letter in the message is replaced with the third letter beyond it in the alphabet.
ROT13 ("rotate by 13 places", sometimes hyphenated ROT-13) is a simple letter substitution cipher that replaces a letter with the letter 13 letters after it in the alphabet.
One is known as the Rosicrucian, or "pigpen," Cipher, in which two letters are put into each section of one grid and one X.
