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Le SphinxPocket cipher device
LE SPHINX was a pocket cryptographic device, developed around 1930 by Société des CodesTélégraphiques Georges Lugagne in Paris (France). The device consists of 10 sliding bars with twoscrambled alphabets each, and should therefore be classed as an alphabet transposition cipher. At thetime, it was advertised as a method for secret writing when sending (radio) telegrams.
The device consists of a metal frame with ten lanes,each of which holds two movable rods withscrambled alphabets. The 20 transposed alphabetsare identified by a number, imprinted in red, and arealways used in pairs, with the upper alphabetrepresenting the clear text and the lower alphabetused for the cipher text.
The rods can be moved by treaded knobs at the rightside which engage gears at the bottom. Two fixedruler windows are present for setting and reading theplain text and cipher text. The source text isprocessed 10 characters at a time.
The device is based on the 1912 invention of a mechanical pocket transposition cipher device by GeorgesLugagne of Boches-du-Rhône (near Marseille, France), which was registered in 1913 as French Patent461.217 [1]. Around the same time, the device was patented in the United Kingdom as British patent23,204 [2]. The device was marketed in France by Lugagne's companies in Paris and Marseille, who hadbecome known for their international telegraphic code books of 1914.
The image on the right shows the original design of1912, which is mechanically less complex, but worksvery similar. It also consists of 20 paired scrambledalphabets, but they are not linked mechanically. Thesliding rods are made of ivory.
In 1931, the design was improved by Lugagne'semployee Paul Godillon, who added the gears andthe 10 treaded knobs at the right hand side. He wasalso responsible for adding the S-shaped gaps ateach end of the alphabet rods, allowing thescrambled alphabets to be coupled in pairs. Hisinvention was patented in France on 4 Feb. 1931 [3].The same patent was filed in the US on 1 December1931 by Albert Gentet [4], who also added themovable index to each window [5].
It is currently unclear where Le Sphinx was manufactured and by whom, but it is possible that it was madeby the famous slide rule manufacturer BARBOTHEU in Paris, who also manufactured the 1912 version[7]. The original Transpositeur is further described in an article by Daniel Tant [8].
'Le Sphinx' is French for 'The Sphinx'. Also see the discussion about the name.1.
This is just an assumption. There is no reason why it could not be used the other way around, as long as both parties do it in the sameway.
2.
ControlsThe diagram below gives an overview of the various features of Le Sphinx. The device measures just 162x 87 x 20 mm and consist of a die-cast metal alloy frame with 10 cogwheel driven lanes, each of whichaccomodates two physically locked scrambled alphabets. This effectively results in 10 differenttransposition ciphers that allow the text to be enciphered in groups of 10 letters.
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On top of the device are two horizontal windows: one for the plaintext and one for the ciphertext. Theposition of the rods or rulers with the alphabets can be altered by means of 10 treaded knobs at the rightside. Each knob drives a cogwheel that in turn engages the teeth at the bottom of a rod. Each position hasa 'click' to ensure that the letters are properly shown in the windows.
Name Le SphinxThe pocket cryptographic device featured on this page, was marketed by Société des CodesTélégraphiques Georges Lugagne, which had offices in Paris and Marseille (France). It is currently unclearunder what name the device was sold, but since the bakelite storage case holds a raised image of asphinx, it is commonly referred to as SPHINX. The metal label at the left side of the device shows thecompany name and the image of the sphinx, with the text 'LE SPHINX' (the sphinx). In order to distinguishit from the Sphinx Cipher Machine, we will call it 'Le Sphinx' .
The name 'Sphinx' originates from the Greek language and represents a mythical creature that generallyconsists of the body of a lion with the head of a human. In Greek tradition it may also have the wings of abird. Sphinx' also exist in Egyptian culture (e.g. Great Sphinx of Giza) [9].
PermutationsWhen calculating the total number of combinations that can be made with the device, we will first look atthe original design of 1912. It had 20 alphabet rulers, 10 of which were intended as the upper alphabetsand the other 10 were the lower alphabets [1]. This gives us 10! (or 3,628,800) possible combinations ofalphabets for the upper half only. As the same is true for the lower half, the total number of combinationswould be 3,628,800 x 3,628,800, which is no less than:
13,168,189,440,000
After the design had been improved by Paul Godillon in 1931, there was no longer a differece between theupper and the lower alphabets, allowing them to be mixed freely [3]. As a result the total number ofcombinations in which the 20 alphabets can be mixed, increased to 20! or:
2,432,902,008,176,640,000
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10! is the mathematical notation for 10 x 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 11.
OperationBefore exchanging a message by means of Le Sphinx, both parties first have to agree which alphabet isused in each position. This is done by quoting the red number that is printed on the top of each rod. This isknown as the settings or the key and is usually pre-arranged between the parties. For the default position,which we have used on this page, the key would be:
01 02 03 04 05 06 07 08 09 1011 12 13 14 15 16 17 18 19 20
Both users should now install the alphabets in the order indicated on the key sheet. Each pair (e.g. 01-11)should be coupled by fitting the S-shaped gap at the top of the lower alphabet into the S-shaped gap atthe bottom of the upper alphabet. For the above key, the setup would be:
Le Sphinx is constructed in such a way that the user can move the rulers by means of treaded knobs atthe right side. There are 5 sets of two knobs. The leftmost knobs (i.e. the larger ones) are used to controlthe rightmost 5 lanes, whilst the rightmost knobs control the leftmost 5 lanes. Furthermore, there are twowindows through which we can read a row of letters. Now rotate the knobs so that the first 10 letters ofthe plaintext are visible in the upper window, for example:
TOPSECRETS
All you now have to do is read the ciphertext from the lower window, which in this case is:
IRUVPYQHWB
All the receiving party has to do, is rotate the rulers so that the ciphertext is visible in the lower window.The original plaintext can now be read from the upper window.
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Cipher securityDespite the large number of possible arrangements of the alphabets, Le Sphinx provides only low-gradecipher security. This is mainly caused by the fact that the arrangment of the alphabets does not changeduring the course of a message. If a message is long enough, it can be solved by frequency analysis. Forvery short messages, the cipher would be relatively secure though.
Another weakness of the system is that there is no provision to send the key at the start of a message.Instead, it has to be pre-arranged. This was also the case with the German Enigma cipher machine,although in that case, procedures were in place to add a random message key.
AlphabetsThe table below shows each of the 20 scrambled alphabets of our device. Note that the alphabets areprinted in the regular order, but that they are shifted by a few positions on each ruler. Also note that thealphabets on the first 10 rulers (1-10) are in ascending order, whilst the alphabets on the last 10 rulers(11-20) are in descending order.
1 ABCDEFGHIJKLMNOPQRSTUVWXYZ
2 CDEFGHIJKLMNOPQRSTUVWXYZAB
3 EFGHIJKLMNOPQRSTUVWXYZABCD
4 GHIJKLMNOPQRSTUVWXYZABCDEF
5 IJKLMNOPQRSTUVWXYZABCDEFGH
6 MNOPQRSTUVWXYZABCDEFGHIJKL
7 PQRSTUVWXYZABCDEFGHIJKLMNO
8 RSTUVWXYZABCDEFGHIJKLMNOPQ
9 TUVWXYZABCDEFGHIJKLMNOPQRS
10 VWXYZABCDEFGHIJKLMNOPQRSTU
11 BAZYXWVUTSRQPONMLKJIHGFEDC
12 DCBAZYXWVUTSRQPONMLKJIHGFE
13 FEDCBAZYXWVUTSRQPONMLKJIHG
14 HGFEDCBAZYXWVUTSRQPONMLKJI
15 LKJIHGFEDCBAZYXWVUTSRQPONM
16 ONMLKJIHGFEDCBAZYXWVUTSRQP
17 SRQPONMLKJIHGFEDCBAZYXWVUT
18 UTSRQPONMLKJIHGFEDCBAZYXWV
19 WVUTSRQPONMLKJIHGFEDCBAZYX
20 YXWVUTSRQPONMLKJIHGFEDCBAZ
References
Georges Lugagne, French Patent 461.217Filed 24 October 1913, granted 23 December 1913. Priority date 23 October 1912.
1.
George Lugagne, British Patent 23,204Filed 14 October 1913, granted 9 April 1914.
2.
Paul Godillon, French Patent 710,604Filed 4 February 1931, granted 27 August 1931.]
3.
Albert Gentet, US Patent 1,956,384Filed 1 December 1931, granted 24 April 1934.
4.
Albert Gentet, French patent 812.481Filed 1 February 1937, granted 11 May 1937.
5.
Pendergrass to Friedman, Classified files of US Patent OfficeUS Government Internal Memorandum, 8 October 1953. pp. 4.
6.
Linialis, Règles Rares ou OriginalesWebsite Linealis.org. Retrieved April 2016.
7.
Daniel Tant, Le transpositeur à permutations secrètesDate unknown. Retrieved April 2016 (French).
8.
Wikipedia, Sphinx9.
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Retrieved April 2016.
Approved for release by NSA on 16 July 2014, E.O. 13526.1.
Reproduced here by kind permission of the president of theAssociation des Réservistes du Chiffre et de la Sécurité de l'Information.
2.
Further information
Le Sphinx on Jerry Proc's crypto pagesOther Lugagne cipher systemsOther manual cipher methodsOther cipher systems
Any links shown in red are currently unavailable. If you like the information on this website, why not make a donation?© Crypto Museum. Created: Friday 15 April 2016. Last changed: Friday, 15 April 2016 - 14:04 CET.
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