Historical cryptography 2. CSCI 470: Web Science Keith Vertanen

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1 Historical cryptography 2 CSCI 470: Web Science Keith Vertanen

2 Overview Historical cryptography WWI Zimmerman telegram WWII Rise of the cipher machines Engima Allied encryption 2

unrestricted submarine warfare Zimmermann hatches plan Keep American busy at home

3 WWI: Zimmermann Telegram 1915, U-boat sinks Lusitania 1,198 drown including 128 US Germany agrees to surface 1st 1916, new Foreign Minister Arthur Zimmermann 1917, unrestricted submarine warfare Zimmermann hatches plan Keep American busy at home Persuade Mexico to: invade US and invite Japan to attack US as well Arthur Zimmermann 3

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accurately in the heat of battle Enter the machine

5 Mechanization of secret writing Pencil and paper Security limited by what humans can do quickly and accurately in the heat of battle Enter the machine Thomas Jefferson's wheel cipher Captain Midnight's Code-o-Graph 5

6 Enigma machine Enigma cipher machine 1918, patented by German engineer Arthur Scherbius Arthur Scherbius A electrical/mechanical implementation of a polyalphabetic substitution cipher 6

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rotates after each letter Rotor set 3 rotors in 3!

8 Rotor (wheel, drum) Enigma rotors Monoalphabetic substitution cipher implemented via complex wiring pattern One of 26 initial positions Geared: rotates after each letter Rotor set 3 rotors in 3!=6 possible orders Eventually increased to 3 out of 5 Navy used even more Possible keys: 3! * 26 3 = 6 * 17,576 = 105,456 8

9 Plugboard Enigma plugboard Operator inserts cables to swap letters Initially 6 cables Swaps 6 pairs of letters Leaves 14 letters unswapped Possible configurations: 100,391,791,500 Total keys: 17,576 * 6 * 100,391,791,500 10,000,000,000,000,000 9

10 Enigma machine Sales initially slow Enigma 1923, Germans find out about failures of communication security in WWI 1925, Scherbius starts mass production German military eventually buys 30,000 Enigma machines 1929, Scherbius dies in carriage accident Arthur Scherbius 10

Step 1: Espionage Cracking the Enigma Disgruntled Schmidt meets with French agent Sells Enigma user manuals Allows replica to be constructed Also codebook and daily key scheme

11 Step 1: Espionage Cracking the Enigma Disgruntled Schmidt meets with French agent Sells Enigma user manuals Allows replica to be constructed Also codebook and daily key scheme French give intelligence to Poles "It is assumed in judging the security of the cryptosystem that the enemy has at his disposition the machine." -German memorandum Hans-Thilo Schmidt 11

orders) Settings of rotors (26 3 settings) Settings of plugboard (6 letter swaps) Unique key per message:

12 Cracking the Enigma Step 2: Poles identify weakness: German's had day code specifying: Configuration of rotors (3! orders) Settings of rotors (26 3 settings) Settings of plugboard (6 letter swaps) Unique key per message: Send 3 letters, encrypted with day key Letters specify new setting of rotors New rotor setting then used for remainder of message Repeat the 3 initial letters Repetition is the enemy of security! Marian Rejewski 12

13 Cracking the Enigma Find patterns in first 6 letters 1 st & 4 th, 2 rd & 5 th, 3 rd & 6 th ciphers of same letter Message 1st 2nd 3rd 4th 5th 6th 1 L O K R G M 2 M V T X Z E 3 J K T M P E 4 D V Y P Z X 1 st A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 4 th P M R X 13

14 Cracking the Enigma Given enough messages: Fill in full table of relations between 3 pairs Message 1st 2nd 3rd 4th 5th 6th 1 L O K R G M 2 M V T X Z E 3 J K T M P E 4 D V Y P Z X 1 st A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 4 th F Q H P L W O G B M V R X U Y C Z I T N J E A S D K 14

15 Find chains Fingerprinting a day key Chains change each day depending on day key 1 st A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 4 th F Q H P L W O G B M V R X U Y C Z I T N J E A S D K A F W A B Q Z K V E L R I B C H G O Y D P C J M X S T N U J 3 links 9 links 7 links 7 links Also for 2 nd & 5 th and 3 rd & 6 th letter pairs # of chains and length, independent of plugboard Catalog 105,456 rotors settings using replica 15

of 6 Poles couldn't build big enough bombes Poles give

16 WWII 1938, Germany increases Enigma security Add two additional rotors, C(5, 3) = plugboard cables instead of 6 Poles couldn't build big enough bombes Poles give research + replicas to Britain & France US Navy bombe Bletchley Park bombe 16

Germans stop repeating day key Turing had already developed

17 Bletchley Park Government Code and Cypher School Height of WWII, 9000 people Battled against improvements to Enigma May 1, 1940 Germans stop repeating day key Turing had already developed technique + machine to crack using a crib instead of repetition of key Alan Turing 17

18 Cribs Cribs Some plaintext you suspect is in ciphertext Ideally also its location e.g. Germans usually broadcast weather at 6 am "wetter" somewhere at start of message German Navy had strongest crypto: 3 rotors out of 8, reflector with 26 orientations Avoided stereotypical messages Allies: Mine area to generate traffic Grid reference as crib Also, stole code books 18

19 Typex Allied encryption British army and air force 5 rotors ECM Mark II (SIGABA) United States 15 rotors No known cryptanalysis M-209 But big, expensive, fragile Portable mechanical device For tactical use 19

20 Navy Department, Office of Chief of Naval Operations, Washington, D.C. CLASSIFICATION: CONFIDENTIAL Date: 27 Dec 1943 CARELESS COMMUNICATIONS COST LIVES The following is a list of some of common violations of security principles: DRAFTING: Unnecessary word repetition Unnecessary or improper punctuation Plain language reply to encrypted dispatch Classification too high Precedence too high Cancellation in plain language of an encrypted dispatch ENCRYPTION: "XYX" or "X"'s for nulls "XX" & "KK" to separate padding from text Same letters at both ends to separate padding from text Continuity of padding Seasonal and stereotyped padding Repetition of generatrices (Ed. Note: CSP-845) Systematic selection of generatrices (Ed. Note: CSP-845) Using plain text column for encryption (Ed. Note: CSP-845) Proper strips not eliminated as prescribed by internal indicator (Ed. Note: CSP- 845) Improper set-up according to date Using system not held by all addressees Failing to use system of narrowest distribution CALLS: Enciphering indefinite call sign Enciphering call signs of shore activities CODRESS might have been used Operation of the cipher machine is as important as the cipher itself! 20

21 Code talkers Machine based encryption Heavy equipment Slow to perform Code talking Use Native American languages Started in WWI with Choctaw Improvise phrases for out-of-vocabulary words "big gun" = artillery "little gun shoot fast" = machine gun 21

22 Navajo code talkers Code talkers WW II Few outsiders knew the unwritten language 3 line message: 20 seconds vs. machine: 30 min Lexicon of 274 words + phonetic alphabet 22

23 Summary History of cryptography WW I Zimmerman telegraph WW II Enigma Allied encryption Code talkers 23

Background Data: Naval Warfare, Battle of the Atlantic, Cryptography, and the Code Game. Battle of the Atlantic Allied Convoys vs.

Background Data: Naval Warfare, Battle of the Atlantic, Cryptography, and the Code Game Randy H. Katz CS Division, EECS Dept. University of California, Berkeley Spring 2013 Battle of the Atlantic Allied