|
|
|
|
|
|
|
Crypto FILL Siemens MSC-2001 → CHX-200 →
The device allows cryptographic keys – that are stored on a 5-level
punched paper tape – to be transferred to a
compatible encryption device
or to a compatible crypto-enabled radio, via the military
14-pin male connector
at the front.
The device measures 175 x 90 x 40 mm and weights approx. 500 grams 2
including the 3.4V battery that is used to retain the keys in the internal
CMOS memory. On top of the device is a narrow slot, through which a standard
5-level punched paper tape can be pulled at an arbitrary speed.
The data is clocked by the sprocket hole.
|
|
|
The device can be used to transfer key(s) straight from the paper tape
to the encryption device, or — when using the A2 model — to store it in
one of the key compartments of the device itself, so that it can be
transferred to one or more encryption devices later. In case of an
emergency, it is possible to wipe all keys in a two-step action.
This procedure is known as ZEROIZING.
The device is suitable for transferring keys to the
Siemens MSC-2001 voice encryption device,
to which it
can be connected directly. For other devices, a suitable adapter or interface
may have to be used.
The device was also used with the
Siemens CHX-200 radio station,
where it was used for loading the cryptographic keys for encryption
and frequency hopping into the CHP-200 processor [1].
The CHX-200
was a high-end military radio system
that was available in various configurations.
It was suitable for the transmission of
morse code (CW),
voice (phone), and data (telegraphy, telex).
|
 |
-
The device appears not to have a model number. Instead the name
Key Gun is used in Siemens litarature.
-
Valid for the A2 model.
|
- S42043-E522-A1
This is the basic version of the Siemens Key Gun. It has a built-in 5-level
paper tape reader that is compatible with the ITA-2 standard,
also known as CCITT-2 and Baudot. It is suitable for transferring a key directly
from tape to the encryption device. As it does not have a built-in memory,
the keys can not be stored inside the device itself.
- S42043-E522-A2
This version has the same features as the A1 version described above, but also
has a built-in memory. Keys can be transferred from the key tape
to the gun, where they are kept in a battery-backed CMOS memory. The gun can
then be used to transfer the key(s) to one or more encryption devices.
The Siemens Key Gun described here, is of this type.
|
The diagram below shows the features of the Siemens Key Gun. At the front
is a 14-pin male connector that can be fitted directly to the
KEY socket of a compatible radio or encryption device. In some cases,
a conversion cable has to be used between the Key Gun and the encryption device.
This is the case with the
Siemens CHX-200 radio station,
for which an NF-7 cable is needed.
At the top of the device is a MODE selector, an indicator light, a START
button and a reader for 5-level punched paper tape. The tape should be inserted
into the reader from the top, and is pulled through it manually. When doing so,
the sprocket hole in the key tape generates a clock pulse to which the
internal electronics are synchronised. The MODE dial is used for selecting
one of eight key compartments. A data transfer is initiated by pressing
the START button.
|
In case of an emergency it may be necessary to wipe all keys that are
stored in the internal memory of the device (A2 model only). This is
usually done by means of a two-step procedure. On the Siemens Key Gun,
the rotorary selector on top of the device is set to (1), where it is blocked
by a white plastic ring mounted below the knob. If knob is then forced
pasted the blocked position (i.e. to CODE ERASE), the plastic notch will
break and the memory is cleared.
This procedure can not be reversed, and the plastic ring has to be replaced
afterwards.
|
The diagram below shows the format of the key tape, which conforms to
the ITA-2 standard.
The actual cryptographic key consists of 50 bits.
As each ITA-2 character is 5-bits long, this means that the key consists
of 10 characters. There are leading and trailing characters, plus
characters to identify the start and validity of the key. Furthermore
extra stunt characters 1 are inserted after each key, to ensure that the
teleprinter – on which the key tape is made – is put in a known state.
The tape starts with a leader that consists of approx. 40 x the letter 'V'.
This is followed by the start character – the letter 'A' in this case –
and the check character, which is always the letter 'J'. The next 10
characters are the actual key words, each of which has 32 possibilities
(25 = 32).
As the key words can be any code from the ITA-2 telegraph alphabet,
including a figures shift (FIGS), it is necessary to put the
teleprinter back in a known state at the end of the KEY. This is done
by inserting the reset sequence: letter shift (LTRS), carriage
return (CR) and line feed (LF).
There is no checksum and
the tape ends with a trailer that consists of approx. 40 x the letter 'V'.
If multiple keys (up to 8) are distributed on a single key tape, the trailer
is also the leader of the following key. In that case, the start character 'A'
– which is used for a single key – should be replaced by a different one that
assigns the key to a specific key compartment of the device.
The following start characters can be used to address the key compartments
1 to 8:
|
X → 1 F → 2 Y → 3 S → 4 B → 5 D → 6 Z → 7 E → 8
|
-
In telegraph speak, 'stunt characters' is a common expression for
the control codes: LF, CR, LTRS, FIGS and SPACE.
In this case they are used to put the teleprinter in a known state.
They are not part of the key.
|
The block diagram below shows how the key gun works. As the tape can be pulled
through the reader at arbitrary speed, the central timing (clock) is
controlled by the sprocket hole in the paper tape. The 5-bit parallel
data from the tape reader is serialised (P/S) and then evaluated (EVAL).
Depending on the setting of the MODE selector on the device and/or the
contents of the key tape, a 50-bit key is read from tape and stored in
the selected key compartment, where it is retained by an internal battery.
When the START-button is pressed, the data is transferred from the selected
key compartment in memory, to the connected communication device
(e.g. MSC-2001).
|
|
The key gun is housed in a strong die-cast aluminium enclosure, that is
painted in a NATO olive green colour. The enclosure consists of two case
shells that are held together by a hinge at the side of the connector.
It can be opened by loosening the screw at the opposite side of the case.
|
Inside the case are two printed circuit boards (PCBs) that are mounted
together in parallel like a sandwich. The PCBs are not fixed inside the
enclosure but are held in place by the case shells. The image on the right
shows the opened Key Gun, with the two small PCBs sticking out.
At the front edge of the PCB stack are the
backup battery
– which has to be replaced every few years –
and the small paper tape reader. At the left is
the wiring to the large 14-pin connector.
At the top right is the control panel, with the CODE selector, the START button
and the LED.
|
|
|
|
Re-assembling the device can be troublesome, as it appears to be difficult
to close the device whilst holding the two PCBs in the appropriate position.
Never use excessive force when closing the device. When the device is
finally closed, replace the screw that locks the two case halves.
|
|
The diagram below shows the pinout of the male 14-pin connector at the front
of the device, as seen from the solder side of the connector. This is the
same as looking into the female socket into which it is inserted.
The pinout is suitable for direct connection to the
MSC-2001.
|
- System ground
- not connected
- not connected
- not connected
- Link E-F-N
- Link E-F-N
- Key input check (input)
- not connected
- (-) Reader voltage (input)
- Clock (output)
- not connected
- Link E-F-N
- Data (output)
- Read/write (output)
|
|
|
|
|
Any links shown in red are currently unavailable.
If you like the information on this website, why not make a donation?
© Crypto Museum. Created: Tuesday 26 December 2017. Last changed: Sunday, 14 April 2024 - 09:14 CET.
|
|
|
|
|
