The Enigma machines produced a polyalphabetic substitution
cipher.
The early monoalphabetic substitution ciphers had been superseded
by polyalphabetic ones, such as the Vigenère cipher in the 16th
century.
They had been considered to be completely secure (le chiffre
indéchiffrable—"the indecipherable cipher") until Charles
Babbage showed that, like monoalphabetic ones, they could be broken
by frequency analysis.
During World War I, inventors in several countries realized that
a purely random key sequence, containing no repetitive pattern,
would make a polyalphabetic substitution cipher, in principle,
unbreakable.
This led to the development of rotor cipher machines which alter
each character in the plaintext to produce the ciphertext, by means
of a scrambler comprising a set of rotors (or wheels) that alter
the electrical path from character to character, between the input
device (in Enigma, a keyboard) and the output device (in Enigma, a
lampboard).
Deciphering enciphered messages involves three stages.
Firstly, there is the identification of the system in use, in this
case Enigma.
Secondly, breaking the system by establishing exactly how
encryption takes place, and thirdly, setting, which involves
finding the way that the machine was set up for an individual
message, i.e. the message key.
Although Kerckhoffs' principle states that a cryptosystem should be
secure even when everything about the system except the key is
known to the enemy, the internal wiring of machines such as Enigma
has so many possibilities, that this second stage is a very
important aspect of breaking them.
The Enigma was potentially an excellent system.
It was designed to defeat cryptanalytic techniques by continually
changing the substitution alphabet through the use of a scrambler
comprising three,or in some cases, four rotors.
Like other rotor cipher-machines, Enigma generated a polyalphabetic
substitution cipher, with a period before repetition that was much
longer than any message, or set of messages, sent with the same
key.
The mechanism of the Enigma consisted of a keyboard connected to
a battery and a current entry plate or wheel (German:
Eintrittswalze), at the right hand end of the scrambler (usually
via a plugboard in the military versions).
This contained a set of 26 contacts that made electrical connection
with the set of 26 spring-loaded pins on the right hand
rotor.
The internal wiring of the core of each rotor provided an
electrical pathway from the pins on one side to different
connection points on the other.
The left hand side of each rotor made electrical connection with
the rotor to its left.
The left most rotor then made contact with the reflector (German:
Umkehrwalze).
The reflector provided a set of thirteen paired connections to
return the current back through the scrambler rotors, and
eventually to the lampboard where a lamp under a letter was
illuminated.
Whenever a key on the keyboard was pressed, the stepping motion
was actuated, moving the rightmost rotor on one position.
Because it advanced with each key pressed it is sometimes called
the fast rotor.
When a notch on that rotor engaged with a pawl on the middle rotor,
that too moved, and similarly with the left most ('slow')
rotor.
There are a huge number of ways that the connections within each
scrambler rotor,and between the entry plate and the keyboard or
plugboard or lampboard,could be arranged.
For the reflector plate there are fewer, but still a large number
of options to its possible wirings.
Each scrambler rotor could be set to any one of its 26 starting
positions (any letter of the alphabet).
For the Enigma machines with only three rotors, their sequence in
the scrambler,which was known as the wheel order (WO) to Allied
cryptanalysts,could be selected from the six that are possible.
TEST RUN: Adobe
Flash Shockwave Player required.
Go to LINK and input the
above highlighted green
text in the decoder as settings shown in picture.
OK! that was easy enough.
Using the Above online
Simulator:
Decode the six lines of
coded text below
Six lines of coded text to decode
Six unique initial rotor settings required
Find the correct three letters to set for each line
Piece together the decoded text
Apply to geochecker and then find cache
And the 
goes to Kyb3r 
