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Key Tape Perforator
- wanted item
The 5224 was one of the first Random Key Tape Perforators, produced by
Reichert Elektronik
in Trier in the early 1950s. The machines were intended
for the production of key tapes for the so-called
mixers: telex-based
cipher machines with truely unbreakable One-Time Pad encryption.
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The machine is based on the principle that One-Time Tape (OTT) encryption
requires two identical key tapes (no more and no less). By punching the two
tapes simultaneously, they are guaranteed to be identical. By installing
a set of (optional) counters, the randomness of the generated key can be
checked.
The image on the right shows a typical 5224 machine as it was used
for many years by the Austrian Army. The noise generator, which is normally
present at the bottom left, is missing from this unit as it was used
in a cascased setup.
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After Germany joined NATO in 1955, it became increasingly difficult
for Reichert to sell highly secure equipment to countries ourside
of Europe and NATO. As a result, the company was moved in 1967
to the neutral country of Austria, where they settled down in the town
of Mils. The company was renamed
Mils Elektronik and its first product
was the successor of the 5224: the Mils A-6723.
It was nearly identical to the 5224, but had a slightly more modern colour.
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The 5224 contained the propretary 2134 optical tape reader
tat was built by Reichert as a replacement of the mechanical tape
readers (e.g. from Siemens) that were commonly used in those days.
As the unit has no moving parts, it is less sensitive to mechanical problems.
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The unit consists of two parts. The upper part is hinged and constains
a lamp the illuminates the tape and shines through its holes.
The lower part contains five light-sensitive diodes, or photo-diodes,
that are fast enough to follow the rapidly moving tape. The signal from
the photo-diodes is then converted to the appropriate level using
transistor amplifiers mounted in the lower part.
The image on the right shows the opened tape reader, with the (yellow)
tape properly inserted in the tape gutter.
Behind the tape, the cable to the lamp in the top section is just visible.
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When the unit is closed,
the tape is 'trapped' inside the gutter so that it
can't move sideways. The tape reader can be opened again
by pressing the red button at the front and folding away the top section.
The full service documentation of the 2134 is available for download below
[2].
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The random key tapes produced by the A-6723 are suitable for use with
virtually any type of telex-based mixing cipher machine (mixer), such as
the Siemens T-43,
the ETCRRM
(used on the America-Moscow Hotline),
the Hagelin TC-52,
the Siemens M-190,
the Philips Ecolex 4
and Mils' own mixers like the ME-640
and the ME-840.
For a complete overview, click here.
The above illustration explains how a mixer works.
Eacht letter from the Plain-text is added to a letter from
a key tape, using an exclusive-OR (XOR) operation
(sometimes called 'module-2 addition).
The advantage of this operation is that it is reversable:
adding the key stream to the cipher text, reveals the plain text again.
The A-6723 is used for generating the red (key) tapes.
For a detailed description of this principle,
read our page about the Vernam Cipher.
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© Copyright 2009-2013, Paul Reuvers & Marc Simons. Last changed: Thursday, 17 July 2014 - 08:43 CET
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