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The circuit is built around a COM9046 single-chip single side band speech
scrambler, made by Standard Microsystems Corporation (SMC) 1
in New York (USA) [2].
The chip runs on a 3.57 MHz crystal 2 and has a centre frequency of 3.5 kHz.
The mirroring frequency is not adjustable, which makes the device the most
simple implementation of a fixed frequency speech inverter,
which offers extremely low security. The effect of the scrambler can easily be
undone by mirroring the audio frequency spectrum once more. During the 1980s,
scanner conversion kits were available.
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The name SVZ is the abbreviation of Sprach Verschleierungs-Zusatz
(speech concealment add-on). It was offered as an upgrade kit for existing
FuG-8 radios
that were already fitted with a
BBC Vericrypt 1100 time domain speech
scrambler. Although the Vericrypt unit offered a far better 3 protection
than the SVZ, there were situations in which the Vericrypt could not be
used. This was the case, for example, when the receiving party did not have
the appropriate cryptographic key.
In such situations, all parties in the network had to turn off their voice
scramblers, making their conversation prone to eavesdropping. By using the
SVZ as a (weak) fall-back, the use of a clear transmission was
avoided. Many existing FuG-8 radios were retrofitted with an SVZ upgrade
in 1991 and 1992. The SVZ can be seen as a smaller alternative for
the earlier Bosch SVZ-8/9.
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SMC was acquired by Microchip Technology Inc. in August 2012.
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The chip was originally designed to work with a 3.58 MHz crystal,
which was used for the colour burst in NTSC television sets
in the US, and was therefore widely and cheaply available
at the time [2].
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Relatively speaking. Although the BBC Vericrypt 1100
offered a much better protection against eavesdropping than
the SVZ module, all speech scramblers,
no matter how complex, are inherently unsafe.
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© Crypto Museum. Created: Thursday 29 June 2017. Last changed: Friday, 23 February 2018 - 21:51 CET.
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