1. M-94 Cylinder Cipher: A Story of Innovation, Intrigue and Deception
The History and Technology of the Enigma Cipher Machine
M-94 Cylinder Cipher: A Story of Innovation, Intrigue and Deception
Ralph Simpson
 Copyright © 2019 CipherHistory.com

2. US Army M-94 Cipher Device
M-94 Cylinder Cipher
US Army M-94 Cipher Device
Main US battlefield cipher device,
25 wheels, each with a unique mixed alphabet
Plaintext arranged on ruler, user selects another row as ciphertext
Key is the order of wheels on axle, labeled inside B-1 to Z-25
Key space very large, (# wheels)!
25! = 83 bit key, greater than Enigma or DES
“Multiplex” cipher, multiple simultaneous vs. serial ciphers – coined by William F. Friedman
M-94 Cylinder Cipher: A Story of Innovation, Intrigue and Deception

3. The History and Technology of the Enigma Cipher Machine
Quiz
What do the following ciphers have in common?
Cylinder cipher
One time pad
Enigma machine
Public key encryption
Vigenère cipher
Wheatstone cipher
Playfair cipher
Cylinder – Thomas Jefferson in 1795, not Bazeries in 1891
One-time pad – Frank Miller in 1872, not Gilbert Vernam and Joseph Mauborgne in 1917
Enigma – Dutch sailors Rudolf Spengler and Theo van Hengel in 1915, not Arthur Scherbius in 1918
Public Key Encryption - James Ellis, Malcolm Williamson and Clifford Cocks of the UK GCHG in 1973, not Whitfield Diffie and Martin Hellman in 1976 and Ron Rivest, Adi Shamir, and Leonard Adleman in 1978
Vigenere – Leon Batista Alberti in 1467, not Blaise de Vigenere who was born 56 years later
Wheatstone – Decius Wadsworth in 1817, not Charles Wheatstone in 1850s
Playfair – Charles Wheatstone in 1854, not Lord Playfair, a friend of Wheatstone who advocated its use
They were all originally credited to the wrong inventor!
M-94 Cylinder Cipher: A Story of Innovation, Intrigue and Deception

4. 1st Invention of Cylinder Cipher
Thomas Jefferson – yes, our third President!
Invented “Wheel Cypher” c.1795
Only one known to exist, in NSA Museum
Uses 36 wheels, Jefferson correctly calculated key space as “372 with 39 cyphers [zeros] added to it”
Jefferson Wheel Cypher
Inspiration may have been Chinese letter locks, popular in France at the time
Wheel Cypher lost to history until discovered in Jefferson’s papers in Library of Congress in 1922, by Dr. John M. Manly
M-94 Cylinder Cipher: A Story of Innovation, Intrigue and Deception

5. 2nd Invention of Cylinder Cipher
Etienne Bazeries
French Army Maj. invention in 1891
20 wheel cipher
Probably not aware of previous Jefferson invention, but would have been aware of letter locks
Broken by Gaetan de Vaires in 1893, so it was
Bazeries Cylinder
not adopted by the French military
Bazeries previously solved a de Vaires cipher
M-94 Cylinder Cipher: A Story of Innovation, Intrigue and Deception

6. 3rd Invention of Cylinder Cipher
Parker Hitt
Hitt did not know of the Jefferson or Bazeries inventions
Lt. James G. Taylor, a classmate in 1911, made a cylinder and strip device to decipher the Army Cipher Disk
Parker Hitt’s first cylinder device, Feb. 1912
In Feb. 1912, Hitt developed a device for deciphering Army cipher disks using 12 pairs of wheels
One of each pair had mixed alphabets, which were on a single shaft in the shop when Hitt noticed a “TH” on first 2 disks… that was the inspiration for the M-94
Hitt invented both the cylinder and strip cipher device, but decided to pursue the strip version
M-94 Cylinder Cipher: A Story of Innovation, Intrigue and Deception

7. Strip Cipher
Parker Hitt pursued the strip cipher version, first deployed in 1934 (M-138) but used earlier for cryptanalysis
Cryptologically identical to cylinder cipher
Used 25 strips of mixed alphabets, later M138-A used 30 strips
1916 Hitt Strip Ciper
Parker Hitt
Advantage over cylinder cipher is ease of having many more alphabet strips
French inventors Arthur Hermann and Georges Lugagne previously developed strip ciphers in 1893 and 1912
1912 Lugagne
Strip Cipher
M-94 Cylinder Cipher: A Story of Innovation, Intrigue and Deception

8. M-94 - A Plethora of Prototypes
M-94 designed by Joseph Mauborgne, based on Hitt invention
First 2 prototypes in early made of red fiber and hard rubber
2 were made of all brass on wooden base (top right)
Later prototypes made of brass and Bakelite (middle and bottom right)
M-94 production model first made in 1921 of aluminum
William Friedman made M-94 with changeable paper strips – M-136 was never accepted
M-94 Cylinder Cipher: A Story of Innovation, Intrigue and Deception

9. Last M-94 Prototype?
M-94 prototype from the estate of Bill Lear, founder of Lear Jets
Lear was radio operator and trainer in Navy in
M-94 Cylinder Cipher: A Story of Innovation, Intrigue and Deception

10. M-94 Acceptance
Mauborgne sent 25 messages to William F. Friedman at Riverbank Labs and Herbert O. Yardley at MI-8 on 4/23/18 for cryptanalysis
Messages were not solved after 6 months, even with a hint
Mauborgne had the M-94 adopted by the Army
William F. Friedman
Joseph O. Mauborgne
M-94 was approved on 4/16/1921 by the Secretary of War
Instructional manual published on Feb. 1922
Total of 9,432 devices were manufactured
8/9/1943 the M-94 was declared obsolete, replaced by M-209
M-94 Cylinder Cipher: A Story of Innovation, Intrigue and Deception

11. Mauborgne’s Challenge Messages
25 messages of 25 characters, all used same key
Hint was given, one message contained “are you”
Friedman expected military type messages, so never solved them
Messages were revealed after Mauborgne’s retirement in 1941
Chlorine and oxygen have not b
Cyanogen is a colorless gas in
Xylonite and artificial ivor
Llangollen is a town in Wales a
Yvette are you going shopping
Orthophosphoric is a compo
Caoutchouc is closely allied
Palladium possesses a power o
Oxydation caused by it probab …
M-94 Cylinder Cipher: A Story of Innovation, Intrigue and Deception

12. Models with Changeable Alphabets
M-136 Cipher
M-137 Cipher
Late in 1933 the M-136 and M-137 were designed
M-136, designed by William Friedman had changeable paper alphabets around the wheels, held in place with springs. Only one prototype was made and proved impractical to use
M-137, complex flat strip cipher device with pulleys and springs, which proved to be unwieldy
Simpler designed M-138 became the model adopted for changeable alphabets in 1934, from Hitt’s design 20 years earlier
M-94 Cylinder Cipher: A Story of Innovation, Intrigue and Deception

13. How to Break the M-94
Number of wheels gives a cycle of repeating ciphers
Selecting a row for encryption means all offsets are the same
A letter cannot encipher into itself, like the Enigma, allowing cribs to attack
After alphabet sequences are known, synoptic tables can aid in faster decryptions
Germans used IBM equipment to break the M-94 after the US entered WW2
By April 1942, messages were routinely decrypted
Signal Corps estimated the M-94 could be broken in 6 hours or up to 2-3 days
M-94 Cylinder Cipher: A Story of Innovation, Intrigue and Deception

14. Cylinder and Strip Ciphers
US Army M-94 Cipher Device
US Army M-138-A Cipher Device
Original invention by Thomas Jefferson still in use 150 years later
Parker Hitt’s inventions of the cylinder and strip devices used for 4 decades - from 1922 to the 1960s
27,000 M-94s and M-138s were made, making them the most used cipher devices of their time
M-94 Cylinder Cipher: A Story of Innovation, Intrigue and Deception

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M-94 Cylinder Cipher: A Story of Innovation, Intrigue and Deception