M-94 (cipher cylinder)

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Encryption cylinder M-94 in the National Cryptological Museum (NCM) of the USA

M-94 (also: CSP 488 ) is the name of a cryptographic device used by the US Army between 1921 and 1943 to encrypt and decrypt messages that are to be kept secret . This is an encryption  cylinder (picture) , which consists of 25 individually rotatable cylinder disks, which can be arranged on a common axis in any order. On the edge of the discs are the 26 capital letters of the Latin alphabet in a different " randomly scrambled " order.

history

The Jefferson roller (around 1790) was an early forerunner of the M-94
Manual for the Bazeries cylinder (1901) with encrypted message to JE SUIS INDECHIFFRABLE German  "I am indecipherable"

As early as 1790, later developed President of the United States Thomas Jefferson (1743 to 1826) based on the known for centuries Ciphering later named after him, Jefferson disk  (image) . It was supposed to serve as a tool for the encryption and decryption of messages, but it was far ahead of its time and was not used. Almost exactly a hundred years later, in 1891, the French officer Étienne Bazeries (1846–1931) presented his “Bazeries cylinder” to the French military authorities. It was a rediscovery of the Jefferson roller.

Without knowing this history, the then captain ( captain ) and later colonel ( colonel ) of the US Army , Parker Hitt , had the same idea in February 1912. The design of the cylinder was further refined by his colleague, then Major (and later Major General ) Joseph Mauborgne , and finally, in 1921, the M-94 cipher system was put into service with the United States Army Signal Corps , i.e. the communications force of the US Army . From 1927 the US Navy also used it , mainly for communication with the Army , and chose the name CSP 488 . Also, military attaches , like navy attaché, and the US Coast Guard used it from 1930. The system was developed by the Americans until the time of the Second World War used inside before it from 1943 through the rotor machine M-209 has been replaced.

Procedure

ATTACKATDAWN was set as plain text here. A possible ciphertext would be (for example, read three lines below) EOLCLEJAQLZH.

The 25 cylindrical disks (diameter 35 mm) are arranged on a 110 mm long spindle in a previously agreed order using a secret key . As a rule, the key and thus the order of the discs remained unchanged for a day. To encrypt a plain text such as ATTACKATDAWN, so German  "attack at dawn" , turns to the individual disks by hand so that the text can be read in a row  (picture left) . In any other line, for example three lines below, you can now read the ciphertext , in the example EOLCLEJAQLZH.

This sequence of letters is sent to the recipient of the secret message, who has his own M-94 and, with knowledge of the day key, can also use the correct sequence of the cylinder disks. He now turns the individual disks so that the ciphertext is next to each other in any line and then looks along the circumference of the cylinder for a suitable line where the plain text “catches his eye”. In this way he is able to read the secret message as plain text again.

Strip scraper M-138-A

The American strip cipher M-138-A is cryptographically equivalent to the M-94 and could be broken by OKW / Chi.

From 1934 there was a cryptographically equivalent strips slide version (via the cipher device M-94 also English strip cipher ) used as M-138-A was called  (picture) . Thirty out of a hundred available rulers were used. Results achieved in this process in 1944, the German cryptanalyst Hans Rohrbach (1903-1993) in his work in the Cipher Department of the High Command of the Wehrmacht a (OKW / Chi) slump . Shortly thereafter, it was dropped by the US Army , but used by other agencies until the 1960s.

literature

  • Friedrich L. Bauer : Deciphered Secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin a. a. 2000, ISBN 3-540-67931-6 .
  • Betsy Rohaly Smoot: Parker Hitt's First Cylinder Device and the Genesis of US Army Cylinder and Strip Devices. Cryptologia 39: 4, 2015, doi: 10.1080 / 01611194.2014.98837 , pp. 315–321.
  • Fred B. Wrixon: Codes, Ciphers & Other Secret Languages. From the Egyptian hieroglyphs to computer cryptology. Könemann, Cologne 2000, ISBN 3-8290-3888-7 , pp. 247-248.

Web links

Commons : M-94  - collection of pictures, videos and audio files

Individual evidence

  1. ↑ Betsy Rohaly Smoot: Parker Hitt's First Cylinder Device and the Genesis of US Army Cylinder and Strip Devices. Cryptologia 39: 4, 2015, doi: 10.1080 / 01611194.2014.98837 , p. 315.
  2. ↑ Friedrich L. Bauer: Deciphered secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin a. a. 2000, p. 475.
  3. ↑ Betsy Rohaly Smoot: Parker Hitt's First Cylinder Device and the Genesis of US Army Cylinder and Strip Devices. Cryptologia 39: 4, 2015, doi: 10.1080 / 01611194.2014.98837 , p. 316.
  4. ^ Fred B. Wrixon: Codes, Ciphers & Other Secret Languages. From the Egyptian hieroglyphs to computer cryptology. Könemann, Cologne 2000, ISBN 3-8290-3888-7 , p. 247.
  5. ^ Fred B. Wrixon: Codes, Ciphers & Other Secret Languages. From the Egyptian hieroglyphs to computer cryptology. Könemann, Cologne 2000, ISBN 3-8290-3888-7 , p. 248.
  6. ↑ Friedrich L. Bauer: Deciphered secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin a. a. 2000, p. 475.
  7. ↑ Friedrich L. Bauer: Deciphered secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin a. a. 2000, p. 129.
  8. ↑ Friedrich L. Bauer: Deciphered secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin a. a. 2000, p. 129.
  9. ↑ Friedrich L. Bauer: Deciphered secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin a. a. 2000, p. 130.