The sent at specific time of day were

The thirdpossible position cannot be the place where word ,,temperature” because tcannot code T and r can not code R                                          temp reture                                      tempr eturePositioningplain text:  tempre tureCodedmessage:         SDTD  ZROIR QOEFZ UJHFFor examplethe word ,,temperature ” is known as a part of the plain text for thefollowing coded message. Once amessage came out which had no letter L in it. A test message has been send andthe operator pressed the letter L every time so it was the only letter thatdon’t correspond in the encoded message. The messages were sent at specifictime of day were about the weather enabled the code breakers to guess whichpart of the message it is. Thy knew that a letter could not be encoded asitself. This helped them to break down the possibilities for which of thepossible code was being used that day so the bombes machine could search forthe day settings.

To break the code Alanbuild a specific machine which was checking possibilities , and this would take around 20minutes.The enigma code wascracked by the allies during the second World War by one mathmagician AlanTuring he created a copy of machine called bombes. The idea of this machine wasthat if the letter was typed it wouldn’t place the same letter in the ciphertext.As an example if someone typed A in code the cipher would be something like Zbut never A .

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Decrypting Enigma code cipherPossibilitiesthat the settings of enigma could be change. This are the possibilitiesthat are displayed above , they are the theoretical possibilities for changingthe plug board setting in the different orientation giving us ways.The possibilities that anumber on the plub board are :   A letter hwas pressed à will go to plug board then à circuit it goes through the 3 rotors whichcipher the plain text 3 times. And then the output returns to the plug board asletter M which is connected together with letter A. 263 = 17576 possibilities of different codes.

The different starting positions of the rotors as theywere changed every day giving The Enigma machine uses keyboard by which the personencrypts the message. Then the message starts to go in the 3 rotors theserotors combine of 3 different types of rotors a fast rotor which after turnswhen a letter is typed. Then another medium rotor which turns when the fastrotor completes a revelation and the slow rotor which rotates when the mediumrotor completes a revolution. After the plain text passed through all threerotors it turns and goes again through the slow, medium , fast rotor .

Germanshad only a choice of choosing 3 rotors from a set of 5 rotors and the rotorscould be set in any orientation. Enigma Machine was used to cipher in 1918 , this machine wasbuild by Arthur Scherbius , but during the World War 2 it was widespread by a Germanintelegence.Enigma Code Cipher:     If the code word has 3 letters then all the lettersnumbered with letter, a” above have been coded with the same Caesar shift. Thesame method applies for the letter numbered with letter,, b” and letternumbered with letter ,,c”.

With the help of frequency analysis we can now breakthe code L F P J P A M B V N B N O U M B V N A V L P X Ea 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 repeatedsets of letters. In this case the long of the key word is most likely to be 3letters , due to distance between repeats is a multiple of 3.LFPJPAMBVNBNOUMBVNAVLPXEConsider 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 thekeyword . Breaking the Vigenère cipher Thisencrypted text cannot be broken easily , even if someone will try without a keythere are 265 ? 1.

2 X 107  possibilities unlike the Caesar cipher with only 25 possibilities.For examplelet the code be ,, ilovedoingmath ” the is going to be ,, find ” The person who is decrypting this , need toknow the key word because there are about 26n  possibilities where n is the number ofthe letters in twine.In thismethod 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 themessages.

As we can see the first raw is normal , the second 1 is shifted byone ,the third one by 2 and so on.The Vigenere Square Frenchman invited one of the best ciphers called vigenere inthe 16th century . It is considered to be a polyalphabetic cipherbecause it uses two or more alphabets letter to encrypt the code. Basically theletters in vigenere cipher are shifted by different amounts .


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