# The sent at specific time of day were

The third
possible position cannot be the place where word ,,temperature” because t
cannot code T and r can not code R

temp reture

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tempr eture

Positioning
plain text:  tempre ture

Coded
message:         SDTD  ZROIR QOEFZ UJHF

For example
the word ,,temperature ” is known as a part of the plain text for the
following coded message.

Once a
message came out which had no letter L in it. A test message has been send and
the operator pressed the letter L every time so it was the only letter that
don’t correspond in the encoded message. The messages were sent at specific
time of day were about the weather enabled the code breakers to guess which
part of the message it is. Thy knew that a letter could not be encoded as
itself. This helped them to break down the possibilities for which of the
possible code was being used that day so the bombes machine could search for
the day settings.

To break the code Alan
build a specific machine which was checking possibilities , and this would take around 20
minutes.

The enigma code was
cracked by the allies during the second World War by one mathmagician Alan
Turing he created a copy of machine called bombes. The idea of this machine was
that if the letter was typed it wouldn’t place the same letter in the cipher
text.
As an example if someone typed A in code the cipher would be something like Z
but never A .

Decrypting Enigma code cipher

Possibilities
that the settings of enigma could be change.

This are the possibilities
that are displayed above , they are the theoretical possibilities for changing
the plug board setting in the different orientation giving us ways.

The possibilities that a
number on the plub board are :

A letter h
was pressed à will go to plug board then à circuit it goes through the 3 rotors which
cipher the plain text 3 times. And then the output returns to the plug board as
letter M which is connected together with letter A.

263 = 17576 possibilities of different codes.

The different starting positions of the rotors as they
were changed every day giving

The Enigma machine uses keyboard by which the person
encrypts the message. Then the message starts to go in the 3 rotors these
rotors combine of 3 different types of rotors a fast rotor which after turns
when a letter is typed. Then another medium rotor which turns when the fast
rotor completes a revelation and the slow rotor which rotates when the medium
rotor completes a revolution. After the plain text passed through all three
rotors it turns and goes again through the slow, medium , fast rotor . Germans
had only a choice of choosing 3 rotors from a set of 5 rotors and the rotors
could be set in any orientation.

Enigma Machine was used to cipher in 1918 , this machine was
build by Arthur Scherbius , but during the World War 2 it was widespread by a German
intelegence.

Enigma Code Cipher:

If the code word has 3 letters then all the letters
numbered with letter, a” above have been coded with the same Caesar shift. The
same method applies for the letter numbered with letter,, b” and letter
numbered with letter ,,c”. With the help of frequency analysis we can now break
the code

L F P J P A M B V N B N O U M B V N A V L P X E

a b c a b c a b c a b c a b c a b c a b c a b c a

In this encoded message in the colour red there are repeated
sets of letters. In this case the long of the key word is most likely to be 3
letters , due to distance between repeats is a multiple of 3.

LFPJPAMBVNBNOUMBVNAVLPXE

Consider the following encoded text:

First computer was developed by a guy who’s name was Babbage
, his theory was that in order to break a code you need to know the length of the
keyword .

Breaking the Vigenère cipher

This
encrypted text cannot be broken easily , even if someone will try without a key
there are 265 ? 1.2 X 107
possibilities unlike the Caesar cipher with only 25 possibilities.

For example
let the code be ,, ilovedoingmath ” the is going to be ,, find ”

The person who is decrypting this , need to
know the key word because there are about 26n  possibilities where n is the number of
the letters in twine.

In this
method we make a key word before encrypting the message to make it more secure.
In this method the key word will shift the alphabet depending on its position.

Vigenere developed his own square to help encode the
messages. As we can see the first raw is normal , the second 1 is shifted by
one ,the third one by 2 and so on.

The Vigenere Square

Frenchman invited one of the best ciphers called vigenere in
the 16th century . It is considered to be a polyalphabetic cipher
because it uses two or more alphabets letter to encrypt the code. Basically the
letters in vigenere cipher are shifted by different amounts .

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