Editing Jefferson disk (section)

== History ==
In the late 18th century [[Combination lock|combination locks]], known in Europe since 15th century, were popularized by [[Edmé Régnier L'Aîné]], and versions of them with letters have been suggested to be the origin of cipher machines.<ref name=":0">{{Cite journal |last=Kruh |first=Louis |date=October 1981 |title=The Genesis of the Jefferson/Bazeries Cipher Device |url=http://www.tandfonline.com/doi/abs/10.1080/0161-118191856039 |journal=Cryptologia |language=en |volume=5 |issue=4 |pages=193–208 |doi=10.1080/0161-118191856039 |issn=0161-1194|url-access=subscription }}</ref>

The first prototype resembling the Jefferson disk was invented by Swedish baron [[:se:Fredrik_Gripenstierna|F. Gripenstierna]] in 1786, but it operated on a different principle: rather than substitute letters with letters, it used 57 disks to substitute letters entered by a cleared official on the one side of device with numbers on the other side of device visible to a clerk.<ref>{{Cite journal |last=Beckman |first=Bengt |date=April 2002 |title=An Early Cipher Device: Fredrik Gripenstierna's Machine |url=http://www.tandfonline.com/doi/abs/10.1080/0161-110291890821 |journal=Cryptologia |language=en |volume=26 |issue=2 |pages=113–123 |doi=10.1080/0161-110291890821 |issn=0161-1194|url-access=subscription }}</ref>

At some point in the 1790s (exact date is not clear<ref name=":1">{{Cite book |last=Jefferson |first=Thomas |url=https://books.google.com/books?id=lOo9DwAAQBAJ&pg=PA106 |title=The Papers of Thomas Jefferson, Volume 37: 4 March to 30 June 1802 |date=1950 |publisher=Princeton University Press |isbn=978-0-691-15001-7 |language=en}}</ref>) [[Thomas Jefferson]] described the device now named after him, with 26 letters on a wheel and estimated 36 to 48 wheels, and its operation in a manuscript.<ref>{{Cite web |title=Cipher Machines |url=https://ciphermachines.com/jefferson3 |access-date=2024-01-13 |website=ciphermachines.com}}</ref> It's commonly claimed that he invented it himself but it is not backed by any evidence, and Jefferson himself didn't imply so in the text.<ref name=":2">{{Cite journal |last=Gaddy |first=David W. |date=October 1995 |title=The Cylinder-Cipher |url=http://www.tandfonline.com/doi/abs/10.1080/0161-119591884033 |journal=Cryptologia |language=en |volume=19 |issue=4 |pages=385–391 |doi=10.1080/0161-119591884033 |issn=0161-1194|url-access=subscription }}</ref> The manuscript was apparently forgotten until it was discovered in 1922 (a year after M-94 entered service, see below) by historian Edmund C. Burnett studying the [[Continental Congress]].<ref>{{Cite book |last=Bedini |first=Silvio A. |url= |title=Thomas Jefferson: Statesman of Science |date=1990 |publisher=Macmillan |isbn=978-0-02-897041-7 |pages=242 |language=en}}</ref> It doesn't appear that the device was ever fabricated,<ref name=":1" /> and Jefferson abandoned the idea after receiving a description of [[Transposition cipher#Columnar transposition|columnar transposition cipher]] from [[Robert Patterson (educator)|Robert Patterson]] in 1803, which he found more practical.<ref>{{Cite web |title=Thomas Jefferson's Codes and Ciphers: II (1790-1803) |url=http://cryptiana.web.fc2.com/code/jeffers2.htm |access-date=2024-01-09 |website=cryptiana.web.fc2.com}}</ref>

In the early 1980s NSA acquired for its museum a large incomplete device of Jefferson's type (picture 1 of this article) with 35 remnant disks (out of 40 originally) and 42 characters, including French letters, on each.<ref name=":2" /> It was dated to the second quarter of the 19th century and it's not clear if it is related to Jefferson despite originating from [[West Virginia]].<ref name=":2" />

When in 1854 Bristol dentist John H. B. Thwaites submitted a "new" cipher (which was in fact just a variant of the [[Vigenère cipher]]) to the ''Journal of the Society of the Arts'', [[Charles Babbage]] mentioned in his response that he likes to use "rings of box-wood placed side by side on a cylinder, and having the twenty-six letters on the circumference of each".<ref>{{Cite book |last= |first= |url=https://books.google.com/books?id=3vdFAQAAMAAJ&pg=PA707 |title=Journal of the Royal Society of Arts |date=1854 |publisher=Society of Arts |language=en}}</ref> However, it's not clear from this description whether the letters were in alphabetic or random order.

=== Basis for later military ciphers ===
A device mechanically similar to Jefferson's but somewhat improved was independently re-invented in 1891 by Commandant [[Etienne Bazeries]], but did not become well known until he broke the [[Great Cipher]], of [[Rossignols]].{{sfn|Friedman|1918|p=225}} In 1893, French mathematician Arthur Joseph Hermann (better known for founding [[Éditions Hermann]]) redesigned the device to use 18 flat wooden or cardboard strips.<ref name=":0" /> Cryptologists in other countries also considered similar devices.

The Bazeries cylinder was the basis for the US "[[M-94]]" cipher machine, which was introduced in 1922 and remained in service until 1942. In 1914, Parker Hitt experimented with the Bazeries device, building one prototype using slides on a wooden frame, with the cipher alphabets printed twice consecutively on the slides, and then another using disks of wood. He forwarded his experiments up the Signal Corps chain of command, and in 1917 [[Joseph Mauborgne]] refined the scheme, with the final result being the M-94.

The M-94 used 25 aluminium disks on a spindle. It was used by the [[United States Army|Army]], [[United States Coast Guard|Coast Guard]], and the Radio Intelligence Division of the [[Federal Communications Commission]] until early in [[World War II]]. The Army changed back to Hitt's original slide scheme with the "[[M-138-A]]" cipher machine, which was introduced in the 1930s and was used by the [[US Navy]] and [[US State Department]] through World War II. The M-138-A featured 100 strips, with 30 selected for use in any one cipher session. It was an improvement in security for the [[State Department]], which during the interwar years had used insecure codes, even in one case a standard commercial [[telegraph]] code.