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Rotor Ciphers

Rotor Ciphers. History. Invented in 1915 by Theo A. van Hengel and R. P. C. Spengler Edward Hugh Hebem developed a rotor machine in the United States in 1917. Arthur Sherbius designed the Engima machine. Marian Rejewski broke the Enigma machine in 1932. Mechanization.

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Rotor Ciphers

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  1. Rotor Ciphers

  2. History • Invented in 1915 by Theo A. van Hengel and R. P. C. Spengler • Edward Hugh Hebem developed a rotor machine in the United States in 1917. • Arthur Sherbius designed the Engima machine. • Marian Rejewski broke the Enigma machine in 1932.

  3. Mechanization • Rotors have 26 positions. • Multiple rotors per machine • User enters a character • Electrical current goes through rotor • Rotor rotates • Next time same character is pressed, different cipher character is produced

  4. Mechanization • Key is pressed • Current goes through rotor • Cipher character lightbulb lights up • Rotor rotates • Reflector (only in Enigma) made decryption the same as encryption, but was flawed

  5. Mechanization (Decryption) • To decrypt, the user must know: • Wheel order – The choice of rotors and their order • Initial position of the rotors – Chosen by operator, changed for each message • Ring settings – Position of the alphabet ring relative to the rotor wiring (shift cipher) • Plug settings - Connections of plugs in plugboard (plugboard connects pairs of letters and switches them before and after main rotor)

  6. Mechanization (Decryption) • To decrypt, the rotors were taken out and turned around from the encryption position to reverse the circuitry. • This was not necessary in the Enigma because of the reflector.

  7. Cryptanalysis • The unsteckered Enigma (without plugboard) was easily broken. • The Polish discovered that they keyboard was arranged ABCDEF, as opposed to QWERTY. • A French spy provided information to the Polish that allowed them to create a replica Enigma machine. • The Polish broke the Enigma machine in 1932 through algebra.

  8. Cryptanalysis • The reflector was a flaw in Enigma machines. • The Polish invented a device known as a cryptologic bomb, which was essentially six Enigma machines. • The Germans constantly made more complex Enigma machines (such as the Kriegsmarine Enigma).

  9. Bibliography • http://www.burningwell.org/gallery2/d/2974-2/ttenigma4.jpg • http://cleavebooks.co.uk/trol/trolc07.pdf • http://en.wikipedia.org/wiki/Cryptanalysis_of_the_Enigma • http://en.wikipedia.org/wiki/Rotor_machine • http://en.wikipedia.org/wiki/Enigma_machine

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