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Hagelin Fax
Fax encryptor
CRYPTOFAX HC-4220 was a fax encryptor
developed in the early 1990s
by Crypto AG (Hagelin) in Zug (Switzerland).
It allowed facsimile messages to be sent
securely by any Group 3 fax unit via analogue PSTN telephone lines,
at speeds between 2400 and 14,400 baud.
The HC-4220 was available from 1994 until it was succeeded
in 2002 by the backwards compatible HC-4221 [B]. 1
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The HC-4220 is housed in a strong die-cast aluminium enclosure that consists of
two parts: the main unit and a detachable control panel. The control panel
consists of a 36-key rubber keypad, a 4-line LCD display and a built-in
card reader at the front. Beteween the display and the keypad are 6 status LEDs.
The image on the right shows the control panel of a typical HC-4220 unit.
It is shown here with a smart card present in the card reader at the front.
The menu-driven unit requires passwords for system manager (SM)
and operator (OP).
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When turning the device on, it first performs a self-test. After approx. 10
seconds it is ready for use. If the battery in the controller is flat,
the real-time clock (RTC) and the actual settings will have been lost.
As a result, the unit resets itself to the factory defaults and the user
is prompted to enter the new configuration.
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The HC-4221 was still available from Crypto AG in 2011.
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The smart card can be used to transfer the cryptographic keys, but it is also
possible to enter the keys manually via the control unit.
Separate passwords are used for the system manager (SM) and the operator (OP).
Crypto Keys (CK) can only be entered by an authorised person and consist
of 21 hexadecimal characters (256 bits). Once a key is entered, it needs to
be activated before it can be used. Once this is done, the LED 'Active Key'
on the control unit will be lit.
If the keys are lost, it is possible to reset the entire device, but that
involves deleting all cryptographic keys as well. All keying material is held
in a battery-backed RAM inside the crypto unit. The backup battery is a
non-rechargeable 3V Lithium cell that lasts for several years before it needs to
be replaced.
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The rather large HC-4220 consists of a sturdy die-case aluminium case.
The top part is taken up by a compact power supply unit (PSU) that can be
removed without disassembling the rest of the unit.
The interior can be accessed by removing 6 bolts from the bottom
and taking off the lid.
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The image on the right shows the interior as seen from the bottom.
The largest board (left) is the modem, featuring various Rockwell modem chips
and some analogue electronics for connection to a PSTN line.
Just visible at the right is the crypto unit,
which is implemented as a closed rectangular
block which can not be accessed. Below the crypto unit is the
interface to the controller.
The interface also contains the backup battery for the crypto keys that are
stored inside the crypto unit.
It is the large blue block at the left.
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As the required 3V Lithium batteries are sometimes very difficult to obtain,
the PCB has been designed in such a way that different types of batteries can
be used, varying from the rectangular blue block shown here, to circular
batteries and batteries with flying wires.
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© Crypto Museum. Created: Sunday 21 August 2011. Last changed: Wednesday, 16 September 2020 - 09:05 CET.
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