ROTOR CIPHER & ENIGMA MACHINE

BY :

SAURABH KAUSHIK (3174)

SARVESH RAWAT (3121)

Taxonomy of Cryptology

Cryptology

Cryptography

Codes

Ciphers

Substitution

Monoalphabetic

Monographic

Polygraphic

polyalphabetic

Transposition

Geometrical

columnar

cryptanalysis

Rotor cipher

A Rotor machine is an electro-mechanical stream cipher device used for encrypting and decrypting secret messages.

A Stream cipher is a symmetric key cipher where plaintext digits are combined with a pseudorandom cipher digit stream (keystream). In a stream cipher each plaintext digit is encrypted one at a time with the corresponding digit of the keystream, to give a digit of the cipher text stream.

Monoalphabetic vs. Polyalphabetic

Monoalphabetic cipher uses fixed substitution over the entire message.

Polyalphabetic cipher uses a number of substitutions at different positions in the message, where a unit from the plaintext is mapped to one of several possibilities in the cipher text and vice versa.

A Rotor

Example

Assumptions:-

A rotor which is designed for first 7 alphabet.

Plaintext of length 5.

Upward rotation.

Example

A B C D E F G

A 0 0 1 0 0 0 0

B 0 1 0 0 0 0 0

C 0 0 0 1 0 0 0

D 0 0 0 0 1 0 0

E 1 0 0 0 0 0 0

F 0 0 0 0 0 0 1

G 0 0 0 0 0 1 0

Starting Configuration Of Rotor

Example

A A A A A A A A AA

B B B B B B B B BB

C C C C C C C C CC

D D D D D D D D DD

E E E E E E E E EE

F F F F F F F F FF

G G G G G G G G GG

Rot. 1 Rot. 2 Rot. 3 Rot. 4 Rot. 5

Example

Suppose, Plain text= DCEGF

D E

C D

E D

G A

F G

Cipher Text = EDDAG

Encryption Procedure :

Example

Revert back the steps followed in encryption procedure!

Decryption Procedure :

ENIGMA MACHINE

Enigma Technology

• Typewriter style cipher machine was a major advance in ease of use and cryptologic strength

• Innovation was the electro-mechanical rotors

• Rotors turn odometer style, giving a new cipher algorithm for each letter in a message

• No printing capability

Keyboard

Plugboard

• The Enigma machine had several cables with a plug at each end that could be used to plug pairs of letters together.

• If A were plugged to B then, on typing the letter A, the electric current would follow the path that was normally associated with the letter B, and vice versa.

Rotors & Reflector

• First rotor rotates each time a character is input.

• The second rotor rotates once each time the first rotor makes one full turn.

• The third rotor rotates once each time the second rotor has rotated completely.

Light Bulb Panel

How it works?

Light Panel

Keyboard

ReflectorLeft

RotorMiddleRotor

RightRotor

EntryDrum

Q W E R T Z I OU

Y X C V B M LN

S D F G KJ

Q W E R T Z I O

Q W E R T Z IU

S D F G KJ

S D F G

P Y X C V B M L

P Y X C V B M LN

P

N

KJ

O

O

M

F

Plugboard

P

A

+

-

+

M

O

- B

A

T

T

E

R

Y

HA

ON

J

X

BF

JB

P ONX

MM

AA

U

H

HH

Copyright © 2016 CipherMachines.com and EnigmaMuseum.com

Enigma rotor and reflector table

They pick any three rotors and one reflector out of these on daily basis.These are the initial configuration of those rotors and reflectors.

How many possible keys are there when you swap each letter of the alphabet with another letter?

26*25*24*23*22*21*20*19*18*17*16*15*14*13*12*11*10*9*8*7*6*5*4*3*2*1

=26!

= 400 000 000 000 000 000 000 000 000

FACTS:

400 septillion keys!

6.5 BILLION PEOPLE IN THE WORLD

31 MILLION SECONDS IN A YEAR

IF EVERYONE IN THE WORLD CHECKED ONE KEY PER SECOND, IT WOULD STILL TAKE 2 BILLION YEARS TO CHECK THEM ALL!

THANKYOU!