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Enigma Z
Numbers-only Enigma Z30 - wanted item

Enigma Z is an electromechanical rotor-based numeric cipher machine, developed around 1930 by Chiffriermaschinen AG in Berlin (Germany). It is the short-lived numbers-only branch of the Enigma cipher machine, and was intended for the encryption of numerical messages, such as (pre-coded) weather report. The letter Z probably stands for Ziffern or Zahlen (numbers). The machine is officially known as model Z30 and by its internal manufacturing designator Ch.16.

The existence of the Z30 was first disclosed by Arthuro Quirantes in April 2004 in an article in Cryptologia [1]. From documents that he had discovered in the Spanish archives, the machine had apparently been offered to the goverment in November 1931, along with other models [1].

In 2015, an actual Enigma Z30 was rediscovered in Sweden, and has since been described by Anders Wik in an article in Cryptologia in August 2016 [3]. The image on the right shows that particular version, taken from its wooden case. It is believed that this version is different from the one that was offered to the Spanish. It is likely to be older, as it features a simpler rotor stepping mechanism and its serial number (Z103) is lower.

The machine has a single-row keyboard with just 10 keys, marked 0 to 9. Likewise, the lamp panel has 10 lamps in a similar arrangement, and the cipher rotors each have 10 contact points at either side. The machine was intended for sending coded numerical messages, such as weather reports and text-based messages that were pre-coded by means of some conversion scheme or short message codebook. We would like to thank Anders Wik for allowing us to reproduce his Enigma Z photographs here [3]. Both versions of the machine are described in more detail below.

Z30 inside its wooden case [3]
Z30 outside the wooden case [3]
Z30 seen from the front [3]
Perspective view of the Z30 [3]
Z30 interior [3]
Z30 interior seen from the top [3]
Z30 rotors [3]
Z30 rotors seen from the side [3]
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Z30 inside its wooden case [3]
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Z30 outside the wooden case [3]
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Z30 seen from the front [3]
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Perspective view of the Z30 [3]
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Z30 interior [3]
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Z30 interior seen from the top [3]
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Z30 rotors [3]
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Z30 rotors seen from the side [3]

From surviving documents, it seems clear that two versions 1 of the machine were developed:

  • Z30 Mark I
    Initial version with Enigma stepping and driven reflector. 2 This version suffers from the double stepping anomaly. Serial numbers are in the range Z-101 to Z-150.

  • Z30 Mark II
    Improved version of which the rotor stepping mechanism is driven by a coupled gear (i.e. by means of cogwheels). Serial numbers are in the range Z-151 to Z-200.
  1. To discriminate between the two models, we refer to them as Z30/I (Z30 Mark 1) and Z30/II (Z30 Mark 2).
    These are not the official designators.

Z30 Mark I   initial version
This version has three rotors with 10 contacts at either side and a single turnover notch each. It has a simple (regular) stepping mechanism, similar to the one of Enigma K and Enigma I, which suffers from the so-called double stepping anomaly [4]. This is known as Enigma stepping. Unlike other machines with Enigma Stepping however, the reflector (UKW) of the Z30/I is driven, which means that it may move when enciphering text. Serial numbers are in the range Z-101 to Z-150. From surviving samples it is known that this model was built and sold to Sweden [2].

The image above shows the features of the Enigma Z30/I. The machine greatly resembles a regu­lar Enigma machine, but is much smaller. Rather than the usual 26 keys and lamps (covering the letters A-Z of the Latin alphabet), it has just 10 in a single row, marked with the numbers 0 to 9.

At the top right is the power selector, which allows the user to choose between HELL (bright) DUNKEL (dark) and AUS (off). The device is powered by two 4.5V batteries connected in parallel, installed in the battery compartment that is located just below the power selector, under the hinged top cover. To offer a clear view, the lamp panel is sloped, just like on the Enigma G.

It is known that the standard version has actually been manufactured and that it was supplied to Sweden an Chile [3]. In Sweden, three units were bought by the Svenska Tändsticks AktieBolaget (STAB), a company of the Swedish entrepreneur Ivar Kreuger, who was known as the Match King. 1 These machines have serial numbers Z101, Z102 and Z103, and are from the first production run.

It has also come to light that during WWII, the German SIGINT and COMSEC agency – OKW/Chi – was interested in the Z30. Norwegian crypto historian Frode Weierud has found a document which shows that an Enigma Z30 with serial number Z106 was given on loan to OKW/Chi in September 1943 [5]. Interestingly, this document is signed by senior cryptologist — Dr. Erich Hüttenhein 2 — which might indicate that the Germans were investiging (or trying to break) a numerical cipher that was used by another country, or that they wanted to use the machine for their own purposes.

  1. Kreuger had control over approx. 70% of the worldwide production of matches at the time. His companies Kreuger & Toll and STAB, were in possession of banks, mines, real estate and other companies [3].
  2. During WWII, Erich Hüttenhain was the chief cryptologist of the Third Reich. After the war, he worked for the new German intelligence service Organsation Gehlen (OG), which eventually became the BND.

Rotors   initial version
The machine has three cipher rotors (I, II and III) that are installed onto a spindle. The spindle can be removed from the machine after unlocking the reflector (UKW) and shifting it aside. The cipher rotors can be placed on the spindle in six possible orders. The UKW can not be removed but can manually be set to any of the 10 possible positions at the start of the procedure.

Rotors of the standard Enigma Z30 [3]

Each rotor has a single turnover notch that is located next to the number 2. It causes a turnover of the adjacent rotor (i.e. the rotor to its left) after the number 9 has been visible in the window on top of the machine. The notch is attached to the rotor body, which means that altering the Ringstellung does not alter its position with respect to the wiring and, hence, does not affect the strength of the cipher [3]. This is identical to the rotors of Enigma D, but different from the rotors of later machines like Enigma K and Enigma I where the notch is attached to the index ring (0-9).

Wiring   initial version
Below is the wiring of the cipher rotors, as recovered by Anders Wik in Sweden, from the machine with serial number Z-103. His findings have been published in Cryptologia in 2016 [3].

Rotor 1234567890 Notch Turnover #
ETW 1234567890      
I 6418270359 2 9 1
II 5841097632 2 9 1
III 3581620794 2 9 1
UKW 5079183642 2 9 1
Stepping   standard version
The standard version of the Z30 has the same stepping mechanism as the Enigma D and the later Enigma I. This means that it features simple stepping – similar to the odometer of a car – and that it exhibits the same double stepping anomaly that was described by David Hamer in 1997 [4].

In the Z30 however, the third cipher rotor from the right (i.e. the one closest to the reflector) can cause the reflector to make a step when its notch is engaged from the rear by the corresponding pawl. This is different from other Enigma machines with simple stepping, such as Enigma D and Enigma K, in which the UKW is settable but not movable.

Power selector
Note that this version has a rather strange type of power selector, which (compared to other Enigma models) is mounted upside down and has three rather than four positions, marked hell (bright), dunkel (dark) and aus (off) respectively. According to the operating instructions [A], the selector should be set to dunkel when the battery is new, in order to prevent the lamps from glowing too bright. Once the lamps are glowing less bright, the selector should be set to hell.

Z30 Mark II   improved version
In November 1931, the Enigma manufacturer — Chiffriermaschinen AG — offered a number of different Enigma machines for sale to the Spanish Embassy in Berlin. This included an offer for the Enigma Z [1]. The photographs on the hastily translated brochure, however, show a machine with an improved cog-wheel driven turnover mechanism, similar to that of the Zählwerk Enigma. It has a cog-wheel release lever at the top left, which is not present on the initial version.

This version also has screw terminals for the connection of an external power source, just like the standard Enigma, and the power selector at the top right has an extra position for this.

It is uncertain whether this machine was actually built, but the image in the brochure (shown on the right) shows a machine with serial number Z155 or Z165, 1 and the wooden lid of that machine is modified to accomodate the release lever at the top left. It seems therefore likely that this was actually a production machine and that the serial numbers ranged from Z-151 to Z-200.

As the serial numbers on the improved version are higher than the ones found on the standard version, we assume that it was developed later, but that the model number (Z30) was the same.

As far as we know, the Spanish Goverment did not buy the Enigma Z30 machines, but it is known that they were sold to other countries, in particular to Sweden and Chile, although this was probably the earlier standard version [2].

Also note that the improved version came with a green contrast filter which is stowed inside the lid of the wooden transit case. It has notches at the short sides by which it can be fitted to the two stubs at either side of the lamp panel. These stubs are not present on the earlier version.

  1. From a better copy [A] it is now clear that the serial number of the machine shown in the brochure is either Z155 or Z153.

Stepping   improved version
A similar brochure, in the original German language was discovered 2013 in the archives of the Dutch Institute for Military History [A]. This might indicate that the machine was also offered to the Dutch Armed Forces, but there is no evidence that the Dutch actually purchased the machine.

It is clear that, although the Z30/II features a coupled gear-driven stepping mechanism, each rotor has only one stepping notch, just like the Z30/I. Unlike the Z30/I though, the Z30/II does not suffer from the double stepping anomaly, which positively affects the machine's period. According to the brochure, the cipher period is calculated as 10 × 10 × 10 × 10 = 10,000.

 Read the German brochure

Improved Z30 with the lid closed
Improved Z30 with the lid open
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Improved Z30 with the lid closed
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Improved Z30 with the lid open

Initial version
The diagram below shows the interior of the Z30 with serial number Z103, after the hinged top cover has been raised. At the center are the cipher rotors, which show great resemblance to those of the regular Enigma machines, albeit with just 10 steps rather than the usual 26. There are three cipher rotors, plus a movable (driven) reflector (UKW) at the left. The ETW is at the right.

At the bottom is the keyboard, which has 10 buttons, numbered from 0 to 9. Above the keyboard is the lamp panel, which consists of a single row with 10 flat-faced light bulbs. In between the keyboard and the lamp panel is a metal frame that can hold up to eight spare light bulbs.

  • Device
    Numbers-only rotor-based cipher machine
  • Purpose
    Encryption of numeric messages such as weather reports
  • Brand
  • Type
  • Model
  • Designator
  • Manufacturer
  • Country
  • Year
  • Customers
    Sweden, Chile, OKW/Chi
  • Rotors
  • Reflector
    see below
  • Turnovers
    1 per rotor, notch fitted to rotor body
  • Plugboard
  • Options
    Extra rotors
  • Dimensions
    238 × 180 × 143 (bare: 216 × 156 × 115 mm)
  • Weight
    5350 g (bare: 4 kg)
Z30 Mark I
  • Reflector
    Driven (10 positions)
  • Stepping
    Regular (Enigma stepping)
  • Period
  • Extras
  • S/N
Z30 Mark II
  • Reflector
    Driven (10 positions)
  • Stepping
    Regular (coupled gear)
  • Period
  • Extras
    Green filter
  • S/N
Known serial numbers
  • Z101
    STAB, Ivar Kreuger
  • Z102
    STAB, Ivar Kreuger
  • Z103
    STAB, Ivar Kreuger
  • Z106
    OKW/Chi, Erich Hüttenhain

  • Z155
    Shown in brochure [A]
Surviving machines
  • Z103
    FRA, Sweden
Related patent
DE 607,638 — 5 March 1930
This patent clearly shows something that resembles the Enigma Z30. A machine with 10 keys and 10 lamps. The patent also claims that the letter-caps over the lamps can be interchanged to provide an extra layer of encryption. To our knowledge, the latter wasn't actually used.

 Read patent DE607638
 Other Enigma patents

  1. Die 'Enigma'-Glühlampen-Chiffriermaschine für Zahlen, Modell Z30
    Enigma Z30 brochure in German language. 5 pages. Undated. 1

  2. La maquina de cifrar números a lámperas incandescentes Enigma Z30
    Operating instructions for Enigma Z30, Mark II (Spanish).
    Chiffriermaschinen AG, Berlin. Undated (probably 1930).
  1. Document obtained from Nederlands Instituut voor Militaire History (Dutch Institute for Military History). Marked: Nuboer 70-4.6. Kindly provided by Tjidde Tempels in January 2013 [6].

  1. Arthuro Quirantes, Model Z: A numbers-only Enigma version
    Cryptologia, April 2004.

  2. Frode Weierud, Enigma History
    Forthcoming publication, expected in 2010.

  3. Anders Wik, Enigma Z30 retrieved
    Cryptologia Volume 40, Issue 3, 2016.

  4. David Hamer: Actions involved in the 'double stepping' of the middle rotor
    Cryptologia, January 1997, Volume XX, Number 1.

  5. ChiMaAG, Empfangsschein Enigma Z-106 1
    Receipt, signed by Willi Korn (ChiMaAG) and Erich Hüttenhain (OKW/Chi).
    30 September 1943. TICOM PAAA, T1717.

  6. Tjidde Tempels, Personal correspondence
    18 January 2013.
  1. Document kindly provided by Frode Weierud [2].

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© Crypto Museum. Created: Monday 14 September 2009. Last changed: Sunday, 16 June 2024 - 13:04 CET.
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