The Enigma MachineInvention of EnigmaHow Enigma WorksScrambling LettersHow to Use an EnigmaSetup: Select (3) RotorsSetup: Rotor Ring SettingsRotor ConstructionSetup: Plugboard SettingsSetup: Initial Rotor PositionEncoding: Pick a “Message Key”Encoding: Transmit the IndicatorEncoding: Reset RotorsDecoding: Initial SettingDecoding: Decode IndicatorDecoding: MessageA Paper Enigma MachineSample EncodeInitial SettingEncode a letter“Manual” ElectricityRolloverBreaking EnigmaVulnerabilitiesUS Army, M-94 Cipher DeviceUS Army, M-209 (Hagelin)Swiss, NEMA (New Machine)Hagelin CD-57Hagelin CX-52 RT (Random Tape)ReihenschieberThe The Enigma Enigma MachineMachineHistory of ComputingDecember 6, 2006Mike KossInvention of EnigmaInvented by Arthur Scherbius, 1918Adopted by German Navy, 1926Modified military version, 1930Two Additional rotors added, 1938How Enigma WorksScrambling LettersEach letter on the keyboard is connected to a lamp letter that depends on the wiring and position of the rotors in the machine.Right rotor turns before each letter.How to Use an EnigmaDaily Setup–Secret settings distributed in code books.Encoding/Decoding a MessageSetup: Select (3) RotorsWe’ll use I-II-IIISetup: Rotor Ring SettingsWe’ll use A-A-A (or 1-1-1).Rotor ConstructionSetup: Plugboard SettingsWe won’t use any for our example (6 to 10 plugs were typical).Setup: Initial Rotor PositionWe’ll use “M-I-T” (or 13-9-20).Encoding: Pick a “Message Key”Select a 3-letter key (or indicator) “at random” (left to the operator) for this message only.Say, I choose “M-C-K” (or 13-3-11 if wheels are printed with numbers rather than letters).Encoding: Transmit the IndicatorGermans would transmit the indicator by encoding it using the initial (daily) rotor position…and they sent it TWICE to make sure it was received properly.E.g., I would begin my message with “MCK MCK”.Encoded with the daily setting, this becomes: “NWD SHE”.Encoding: Reset RotorsNow set our rotors do our chosen message key “M-C-K” (13-3-11).Type body of message:“ENIGMA REVEALED” encodes to “QMJIDO MZWZJFJR”.Complete message is then:NWDSHE QMJIDO MZWZJFJRDecoding: Initial SettingSetup is the SAME for encoding and decoding. Set rotors to “M-I-T” (13-9-20).Decoding: Decode IndicatorType in message indicator: “NWDSHE”.Confirm it decodes to “MCK MCK” (a valid message key).Decoding: MessageSet rotors to “M-C-K” (13-3-11)Type remainder of message:“QMJIDO MZWZJFJR” becomes“ENIGMA REVEALED”!A Paper Enigma MachineEach rotor is modeled as a strip of paper; the electrical contacts are replaced by matching letters on left and right side of the strip.Keyboard and Lamps are replaced by a vertical list of letters on the right.Reflecting rotor is replaced by a matching group of letters on the left.Plugboard and rotor “ring settings” are not modeled.Sample EncodeRotor order: I, II, IIIRotor setting: M, C, KEncode the letter “E”Initial SettingRotors I, II, and III“Window settings” of “M-C-K”Encode a letter(First!) Advance the right-most rotor (III) by moving it up one row.“Manual” ElectricityStart at “E” on the right column.Trace through each rotor, matching like letters.RolloverWhen the “notch” arrow reaches the window, move the wheel to it’s left up one row before encoding.When the center wheel arrow reaches the window, remember to move BOTH center and left wheels!Breaking EnigmaPoles intercept commercial Enigma in the mail, 1928Recruit math students at Poznan University, 1929Poles (Rozycki, Zygalski, Rejewski) break the 3-rotor machine, 1932-1939Overwhelmed by 2 new rotors in 1938Poles hand over methods and machine copy to British and French in 1939Government Code & Cipher “School” created at Bletchley Park, 1939VulnerabilitiesEncryption of doubled indicators reveals information about rotor positions.Operators choose poor message keys (e.g., “BER”, “LIN”, “HIT”, “LER”, “JJJ”, “QWE”).Letter never encrypts to itself (allows known plaintext attack).US Army, M-94 Cipher DeviceUS Army, M-209 (Hagelin)Swiss, NEMA (New Machine)Hagelin CD-57Hagelin CX-52 RT (Random
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