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Rotor Gretag ← TC-53
Online cipher machine
- this page is a stub
TC-58, also referred to as Telecrypto 58, KFF-58 1 or KFF.
is an electromechanical rotor-based
cipher machine,
developed in 1958 by Gretag AG in Regensdorf (Switzerland),
as the successor to the TC-53.
Like the TC-53, it uses electrical rotors,
but introduces automatic synchronisation of the cipher
stream, making it more suitable for use on noisy HF communication circuits.
The machine was initially developed for the Swiss Army, but was also sold to the
Austrian Army.
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A complete setup consists of a KFF-58 teletypewriter
with a TC-58 cipher attachment mounted on top.
The cipher attachment has 12 cipher rotors, of which the leftmost four
are part of the electrical scrambler, whilst the rightmost eight rotors control
the stepping of the scrambler.
The image on the right shows a typical TC-58 unit. The current position of
the rotors is visible through two sets of windows. Below the windows are
two rows of switches: eight red ones and twelve black ones. The black switches
are used for setting the initial position of the rotors.
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For the generation of unique keys, some machines were equipped with a
key production device or SPG. When present, the SPG
was fitted in the empty space at the left of the front panel. It is not present
on the machine shown here. As it was a classified device, intended for adding
security, it was not supplied to foreign customers like the Austrian Army.
In reality however, the SPG reduced the cipher security, as the
generation of – supposedly random – keys was anything but random.
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KFF is the abbreviation of Krypto-Funk-Fernschreiber (Crypto Radio
Teleprinter). Although this name refers to the teleprinter part of the
setup, it is commonly used as a designator for the entire system.
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- Automatic synchronisaton of the cipher stream
- Rotors can be adjusted in both directions
- Fitted to the teleprinter (rather than a separate device)
- Incompatible with TC-53
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This is the teleprinter that provides the base for the TC-58 cipher unit.
Unlike most teleprinters, which use the
5-bit ITA-2 data format,
the KFF uses Gretag's unique 14-bit format, in which each character is
construction from a series of segments.
➤ More information
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This is the actual TC-58 cipher unit. It is installed on top of an existing
KFF-58 teleprinter, which drives it mechanically and electrically.
The hinged front panel is locked with a physical key and protects the
cipher wheels.
The initial position of the rotors can be set with the 12 black switches
at the front panel.
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Key production unit (SPG)
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Some TC-58 units were equipped with a so-called
Schlüsselproduktionsgerät (SPG) — a key production device
intended for the generation of random keys, as opposed to manually
selected keys which would hardly be random. The same SPG device
was used with the earlier TC-53.
The device was classified and was therefore not supplied to foreign customers.
In reality, it provided little extra security, if any.
➤ More information
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Although the KFF-58 can be used with virtually any type of
shortwave (SW) radio system, it was commonly used in combination with the
SE-222 station made by Zellweger
in Uster (Switzerland).
Further information on this radio will be made available in due course.
➤ More information
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- Walter Schmid, Der Krypto-Funk-Fernschreiber KFF-58
October 2008.
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© Crypto Museum. Created: Friday 03 November 2017. Last changed: Tuesday, 11 April 2023 - 07:17 CET.
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