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OTT Mixer Germany Lorenz M-190 →
One-time tape cipher machine · 1956
- this page is a stub
The Lorenz Mischer 544 (English: Lorenz Mixer 544), also known as
Mi544 or LoMi, was a one-time tape (OTT)
cipher machine (mixer),
developed around 1956 by
C. Lorenz Aktiengesellschaft
in Stuttgart (Germany). It was used by the German Army (the Bundeswehr),
and within NATO. The machine was compatible with
other OTT cipher machines — such as the Dutch
Philips Ecolex II and
Ecolex IV,
and the Norwegian ETCRRM —
but only if key tape was shifted by one position [1].
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The Mi-544 is housed in an extremely large die-cast aluminium
enclosure that measures 680 x 520 x 330 mm and weights no less than 56 kg.
The device is intended as an add-on for existing teleprinter installations
and should be connected between the teleprinter and the line. It takes
the 5-level output from the teleprinter and mixes it with the characters
from a key tape, using XOR arithmetic, also known as modulo-2 addition.
The image on the right shows the initial version of the Mi544 in its typical
green hamerite finish. At the top is a resessed bay for the key tape.
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The One-Time Tape
principle with its XOR arithmetic, is described in
US patent 1,320,729 and is known
as the Vernam Cipher, named after
the American inventor Gilbert Vernam who invented it in 1917, along with the
One-Time Pad (OTP).
When used correctly (i.e. the key tape contains truely random characters,
is used only once and is destroyed after use) the cipher is unbreakable.
The Mi-544 was developed in the mid-1950s, and was first delivered to
the Bundeswehr in 1956. It was first described by Lorenz employee
G. Grimsen in SEG·Nachrichtenheft 4 of 1956 [4].
This version has the bay for the key-tape cassette at the top.
In 1958, it was succeeded by the slightly improved Mi 544B, which
had the key-tape bay at the front right.
The price for a bare Mi-544B in 1963 was DM 11,260 (EUR 5,630), or
DM 15,885 (EUR 7,942) when the SYZ-634 synchroniser was also required [3]. 1
In the 1970s, the Mi544 was superceeded by the
Siemens M-190.
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These prices do not include the teleprinter to which it had to be
connected.
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At present, this page only acts as a placeholder for (future) information
about the Mi544 (LoMi).
Mi544 Primary version of 1956, with key-tape bay at the top Mi554B Improved version of 1958, with key-tape bay at the right
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The 5-level key tape was supplied in the metal container, or cassette,
shown in the image on the right. The cassette can be locked with a
cross-key, and has an internal paper feed that is constructed in such
a way that the paper can only be pulled out and cannot be put back in.
At the top is a raised section the holds the locking mechanism and a
window through which the user can check the tape supply. The cassette
was installed in a bay at the top of the Mi-544, or vertically at the
front right of the Mi-544B.
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- Lorenz Mischer 544
- Lorenz Mixer
- Mi544
- LoMi 544
- LoMi
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Principle One-Time Tape (mixer) Alphabet 5-level ITA-2 Transmission 50 baud (optionally 45.5 baud) 1 Speed 428 cpm at 50 baud (368 cpm at 45.5 baud) Interface 2-wire single-current, 40 mA Distortion 40% max. Tape diameter 190 mm max. Synchroniser Option Mains power 220V AC (50-60 Hz) Internal 60V DC, 120V DC Consumption 150W (without peripherals) Lamps 6V, 0.3A Fuses F1: 0.1A, F2: 0.3A, F3: 2A Dimensions 330 x 520 x 680 mm Weight 56 kg
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Requires the swapping of a cogwheel.
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Document kindly provided by Heinz Blumberg [2].
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Document kindly provided by Heinz Blumberg [2].
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© Crypto Museum. Created: Monday 02 February 2015. Last changed: Tuesday, 25 January 2022 - 23:27 CET.
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![Lorenz Mi-544B. Image kindly provided by Heinz Blumberg [2].](img/lomi_1_thumb.jpg "image # lomi_1_large.jpg"){kind=small}
![Interior of the Lorenz Mi-544B. Image kindly provided by Heinz Blumberg [2].](img/lomi_2_thumb.jpg "image # lomi_2_large.jpg"){kind=small}
![Lorenz Mi-544B. Image kindly provided by Heinz Blumberg [2].](img/lomi_1_large.jpg)
![Interior of the Lorenz Mi-544B. Image kindly provided by Heinz Blumberg [2].](img/lomi_2_large.jpg)
