Rotor CiphersRotor Ciphers

HistoryHistory

Invented in 1915 by Theo A. van Hengel Invented in 1915 by Theo A. van Hengel and R. P. C. Spenglerand R. P. C. Spengler

Edward Hugh Hebem developed a rotor Edward Hugh Hebem developed a rotor machine in the United States in 1917.machine in the United States in 1917.

Arthur Sherbius designed the Engima Arthur Sherbius designed the Engima machine.machine.

Marian Rejewski broke the Enigma Marian Rejewski broke the Enigma machine in 1932. machine in 1932.

MechanizationMechanization

Rotors have 26 positions.Rotors have 26 positions. Multiple rotors per machine Multiple rotors per machine User enters a characterUser enters a character

Electrical current goes through rotor Electrical current goes through rotor Rotor rotatesRotor rotates Next time same character is pressed, Next time same character is pressed,

different cipher character is produced different cipher character is produced

MechanizationMechanization

Key is pressedKey is pressed Current goes through Current goes through

rotorrotor Cipher character Cipher character

lightbulb lights uplightbulb lights up Rotor rotatesRotor rotates Reflector (only in Reflector (only in

Enigma) made Enigma) made decryption the same as decryption the same as encryption, but was encryption, but was flawedflawed

Mechanization Mechanization (Decryption)(Decryption)

To decrypt, the user must know:To decrypt, the user must know: Wheel order – The choice of rotors and their orderWheel order – The choice of rotors and their order Initial position of the rotors – Chosen by operator, Initial position of the rotors – Chosen by operator,

changed for each messagechanged for each message Ring settings – Position of the alphabet ring relative Ring settings – Position of the alphabet ring relative

to the rotor wiring (shift cipher)to the rotor wiring (shift cipher) Plug settings - Connections of plugs in plugboard Plug settings - Connections of plugs in plugboard

(plugboard connects pairs of letters and switches (plugboard connects pairs of letters and switches them before and after main rotor) them before and after main rotor)

Mechanization Mechanization (Decryption)(Decryption)

To decrypt, the rotors were taken out and To decrypt, the rotors were taken out and turned around from the encryption turned around from the encryption position to reverse the circuitry.position to reverse the circuitry.

This was not necessary in the Enigma This was not necessary in the Enigma because of the reflector.because of the reflector.

CryptanalysisCryptanalysis

The unsteckered Enigma (without plugboard) The unsteckered Enigma (without plugboard) was easily broken.was easily broken.

The Polish discovered that they keyboard was The Polish discovered that they keyboard was arranged ABCDEF, as opposed to QWERTY.arranged ABCDEF, as opposed to QWERTY.

A French spy provided information to the A French spy provided information to the Polish that allowed them to create a replica Polish that allowed them to create a replica Enigma machine.Enigma machine.

The Polish broke the Enigma machine in 1932 The Polish broke the Enigma machine in 1932 through algebra.through algebra.

CryptanalysisCryptanalysis

The reflector was a flaw in The reflector was a flaw in Enigma machines.Enigma machines.

The Polish invented a The Polish invented a device known as a device known as a cryptologic bomb, which cryptologic bomb, which was essentially six Enigma was essentially six Enigma machines.machines.

The Germans constantly The Germans constantly made more complex made more complex Enigma machines (such as Enigma machines (such as the Kriegsmarine Enigma).the Kriegsmarine Enigma).

BibliographyBibliography

http://www.burningwell.org/gallery2/d/2974-2/http://www.burningwell.org/gallery2/d/2974-2/ttenigma4.jpgttenigma4.jpg

http://cleavebooks.co.uk/trol/trolc07.pdfhttp://cleavebooks.co.uk/trol/trolc07.pdf http://en.wikipedia.org/wiki/http://en.wikipedia.org/wiki/

Cryptanalysis_of_the_EnigmaCryptanalysis_of_the_Enigma http://en.wikipedia.org/wiki/Rotor_machinehttp://en.wikipedia.org/wiki/Rotor_machine http://en.wikipedia.org/wiki/Enigma_machinehttp://en.wikipedia.org/wiki/Enigma_machine