Module Four

Scytale n used by spartans in 400bc wrap message

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Scytale n used by Spartans in 400B.C. – wrap message around wooden dowel n diameter and length are the keys to the cipher. Caesar cipher n Monoalphabetic substitution – only used one alphabet n Specifically - Involved shifting the alphabet three letters n Known as C3 (Caesar shift 3 places) Cipher Disks n Two concentric disks with letters on the edge n Can be used to match up letters Arabs invented cryptanalysis n Arab philosopher al-Kindi wrote Manuscript on Deciphering Cryptographic Messages Thomas Jefferson - disks n 1790 developed device with 26 disks that could be rotated individually n Message would assembled by lining up the disks to the alignment bar n Then the bar was rotated a given angle and the resulting letters were the cipher text n The angle of rotation of the alignment bar was the key Disks used extensively during the civil war
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UNIX – ROT13 shift the alphabet 13 places Hagelin Machine n Developed in 1920 by Boris Hagelin – Stockholm Sweden n Known as the M-209 in the US 1920’a Herbert O. Yardley was in charge of U.S. MI-8 (a.k.a. the Black Chamber) n Cracked codes of a number of Nations n Gave U.S edge in Japanese negotiations in 1921-1922 n U.S. State Department shut down MI-8 n Upset, Yardley published book The American Black Chamber 1931 n Japanese got new codes n Yardley is father of American Cryptology Japanese Purple Machine After Yardley William Friedman resumed cryptanalysis for U.S. Army Broke the new Japanese cipher. U.S. Navy broke the Purple Machine naval codes during World War II German Enigma Machine n Polyalphabetic substitution cipher - using mechanical rotors n Developed in 1919 by Dutchman Arthur Scherbius obtained US Patent for Berlin firm n Polish cryptanalyst broke the three-ring system with card file of all 6 x 17,576 possible rotor positions n 1938 German went to six rings n In 1938 Poles and French developed the “Bombe” there own Enigma machine n British took over in 1940 and by 1943 British and US had high speed “bombe” n Disks have 26 contacts on each side, to communicate with each neighboring disk one of them makes contact with the other disk n Also rotates the disks after encryption of each letter n Rotates next highest rotor like a “gas pump” – polyalphabetic n Other rotor machines – German Enigma, Japanese Red, Japanese Purple and American SIGABA “Big Machine” Cryptographic Technologies Symmetric Key - (Private Key or Secret Key) Asymmetric Key – (Public Key) Public Key cannot derive the private Key Private Key Cryptography is 1,000 times faster than public key cryptography Vigenere Polyalphabetic Cipher n Caesar is a subset of the Vigenere Polyalphabetic Cipher n Vigenere used 26 alphabets n Each letter of the message corresponds to a different alphabet n Subject to guessing the period, when the alphabet changes Modulo returns the remainder over the modulo value C=(M+b) mod N Where C = Cipher Text M= Message B = fixed integer N = size of alphabet
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Scytale n used by Spartans in 400BC wrap message around...

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