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← Racal Voice
The image on the right shows a typical MA-4777C. The device is housed in
a ruggedized green metal enclosure. At the front is the
connection for the handset.
In the MA-4777C this is a 6-pin
U-229 socket for
connection of a standard US or NATO handset
or headset.
On the MA-4777A, a military 7-pin 105 socket,
similar to the one at the rear panel,
is present at this location. It is for connection to
Clansman equipment.
The connector at the rear
is for connecting the MA-4777 to a transceiver,
using an adapter cable that is suitable for the radio.
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The only controls that are available on the MA-4777 are the
two rotary selectors on the front panel.
The upper one is for setting the audio volume, whilst the lower one
is used to select one of four key compartments,
marked A, B, C and D. Clear speech is selected by setting the lower switch
to the Clr-position. Setting both switches to Z, purges
or zeroizes the keys instantly.
Production of the MA-4777 started around 1987 with the MA-4777C.
Over the years, the design was improved and simplified several times,
but the Crypto Module remained the same. The latest version is the
MA-4777A, which was produced from 1994 until the end of its life cycle
in 2011.
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Typically, a single letter suffix (A, B or C) is used to designate the three
different MA-4777 versions. In some cases, a second suffix letter is
present to indicate the type of crypto module that is fitted.
At present, the following suffixes are known:
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When the Racal proprietary MX-4437 crypto module is fitted, four
modes of secure operation are provided. The keys for these modes have to
be loaded into the MA-4777 by means of the battery powered
MA-4073 programmer, that is connected
to the audio socket at the front panel.
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Special
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When the Special Crypto Module is installed, two modes of secure
operation are provided. The keys for these modes are loaded with a
special fill unit and the Optical Fill Interface MA-4549A.
The image on the right shows such an optical fill interface.
It is powered from the device to which it is connected.
Once the interface is connected to the MA-4777, the special fill
unit is placed in the cradle, with its 'eye' towards the rear.
To date we have not seen the required fill device for this method
of key loading
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DS-102
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If the MA-4777 was issued with the MA-4487 Crypto Module,
that features the SAVILLE algorithm,
a DS-102 compatible
key loader had to be used. However, as the fill interface of the
MA-4777 is not compatible with DS-102,
the special MA-4778 interface was developed.
The image on the right shows the MA-4778, which has a fixed cable
for connection to the MA-4777 or a compatible radio. The MA-4778
itself has to be filled from a DS102 compatible key loader first,
such as the KYK-13.
➤ About the MA-4778 interface (DS-102)
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In order to allow secure communication with other MA-4777 units,
or with a radio that has a built-in compatible crypto unit (e.g.
PRM-4515 Cougar),
the following conditions must be met:
All units must be fitted with the same crypto module,
the must all have the same crypto variables (keys) loaded,
and the same key compartment (A, B, C or D) must be selected on
all devices.
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The cryptographic keys are stored inside the MA-4777 in a volatile
static memory (RAM) that is retained by a Lithium backup battery.
In case security is comprimised, the crypto keys can be deleted
instantly, by turning and holding both rotary switched fully
counter-clockwise to the Z-position. For this you need both hands
as the switches are momentary.
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The MA-4777 is housed in a sturdy slim-line metal enclosure with
separate front panel and rear panel assemblies that are watertight.
It can be opened by removing the outmost two bolt from the rear
panel, after which the rear panel can be
separated and disconnected
from the rest.
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Once this is done, the complete interior
can be removed by pulling the front panel away from the case.
Inside the MA-4777 are two
printed circuit boards (PCBs) that are mounted to a die-cast aluminium
frame that in turn is attached to the front panel.
The two PCBs are mounted opposite of each other, with a large 34-pin
header connecting them. One PCB hold the
control circuits whilst the
other one is the Crypto PCB.
The Crypto PCB can be separated from the rest, by releasing the four
bolts in the corners, after which it can be lifted away
from the 34-way connector.
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The MA-4777 is powered from the system to which it is connected and
accepts a DC input between 8V and 22V DC (into either of its sockets).
As the power lines of the two connectors are internally connected, the
power then becomes available on the other connector (as an output).
When the MA-4083 fill gun is used to load the key variables, the
MA-4777 will supply power to it. In the same vain, the MA-4549
optical fill interface will also be powered by the MA-4777.
When the MA-4777 is disconnected from its power source it will retain
the key variables (stored in its internal memory) for a period depending
on the crypto module that is fitted. With the typical Racal
MA-4437 module, the keys will be retained for at least 3 years.
When the Special Crypto Module is fitted it will be > 2 hours
(typically approx. 5 days).
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For secure communication, the MA-4777 was fitted with a voice
encryption/decryption module (or Crypto Module, or Crypto Unit), that was
installed on the Crypto Board.
Various types of crypto modules were
available for different customers and different needs. Note that each type
requires a different version of the MA-4073 Programmer
and/or the MA-4083 fill gun.
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The standard crypto module that was delivered to most customers, is
the MA-4437 shown in the image on the right.
It uses a Racal-proprietary cryptographic algorithm and can hold
up to four cryptographic keys, each of which consists of 120 bits.
The key is constructed in the MA-4073 Programmer from 36 octal digits
(0-7, or 3 bits) plus a 12-bit fixed prefix (all '1's by default).
The crypto module can encrypt or decrypt the radio's digital 16 kb/s CVSD
modulated data stream, but not both at the same time. That means that it
can only be used in simplex mode.
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The keys are stored inside a Harris MH-6504-9 4096-bit CMOS memory,
that is located at the upper side of the module.
When using this module, the keys are retained by a built-in battery
for more than 3 years, even when the radio is disconnected from the power [A].
This is known as long crypto retention.
The presence of a crypto module causes a 128 ms delay in the audio path,
which is needed for crypto processing.
At the start of a transmission is a 96 ms preamble.
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This is a different module that was supplied to some European customers.
It is not compatible with the MA-4437 and requires a different version of
the programmer and the fill gun ('G' instead of 'C'-version).
Nevertheless, the key length seems to be identical (120 bits) [3].
MA-4487 boards are generally red, whilst MA-4437 boards are green.
Although it is possible that this board contains the
SAVILLE encryption algorithm,
but it is more likely that it is 'just' a variation
of the standard MA-4437 module. Like the MA-4437 is sends a 96 ms preamble.
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The layout of the MA-4487 board is identical to that of the MA-4437 and
the 4 chips are also similar, except for the fact that the product code of
the two large chips (one at the top and one at the bottom)
have a C-suffix (MT70083C versus MT70083, and MT70084C versus MT70084).
Like the MA-4437, this board can hold up to 4 crypto keys,
all of which are available to the user.
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VINSON
Special module — wanted item
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When using this module, only two cryptographic keys can be stored in the
device. Furthermore, the crypto keys are only retained for a
minimum of 15 minutes (typically several hours) when the device is
disconnected from its power source. This principle is known as
short crypto retention.
The image above shows a white BID/420 module, which is the British
version of VINSON.
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If the crypto board of the MA-4777 has been removed, four
wire loops have to be inserted in the socket the normally contains the
crypto module. These wire loops ensure that the 16 kb/s CVSD
data is properly bypassed.
The drawing on the right shows the
position of the four wire links, as seen from the top. Note the position
of the notch, which is close to the edge of the PCB.
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When the power suppy of the MA-4777 is disconnected, the crypto
keys are retained for at least 15 minutes (typically several hours),
to ensure that the batteries can be swapped without loosing the keys.
Normally, a large capacitor (known as a 'SuperCap') on the
control board ensures that sufficient power is supplied to the
crypto module during this period. In Racal terminology, this is known as
short crypto retention. It was typically used in combination
with the VINSON module.
Depending on the requirements of the customer, a Lithium battery
could be installed in place of the SuperCap, to ensure that the
keys were retained indefinitely (typically more than 3 years)
when the main battery was disconnected. This is known as
long crypto retention. Although it was typically used
with the MA-4437, any combination of retention/crypto module was
possible.
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All crypto modules have the same footprint and can be installed
in any PRM-4735. They are also used in other Racal crypto-capable
products, such as the PRM-4515
and the MA-4777.
A full list of compatible products is given below.
Note that devices are only interoperable if they
use the same algorithm (i.e. the same colour crypto module),
the same frequencies and the same keys.
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VINSON —
Please note that the devices marked with a * do not
use a Racal crypto module, but a proprietary VINSON compatible module,
that is interoperable with a Racal device that has the mysterious
VINSON module installed. VINSON uses the highly secret
SAVILLE encryption algorithm
developed by GCHQ and NSA.
➤ More
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The three version of the MA-4777 each have a different audio connector at
the front panel. The radio socket at the rear is the same for all three
variants, although the impendance may be different. The pinout of the
sockets for each model are given below.
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This version is intended for Clansman compatible equipment. It can be recognised
by the 7-pin Clansman-style 105 female audio socket at the front panel. Furthermore
the circuit inside the MA-4777 is customised to cope with the Clansman signal levels.
The audio socket (marked H for Headset),
at the front panel of the MA-4777/A is wired as follows:
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- Mic in or Fixed Level Audio (FLA) or program input
- Mic return or Wideband programming
- Power out
- Audio out
- Ground
- PTT or 4 kb/s data or key fill data
- Squelch or CTS output
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The Radio socket (marked R) at the rear end of the MA-4777 is identical
for all three versions (A, B and C) and is wired for Clansman equipment.
Any transition to other equipment is made in the cable from the MA-4777
to the radio. For Clansman equipment a straight through (1:1) cable is used
between the MA-4777 and the radio. The radio socket R at the rear
is wired as follows:
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- Audio to transmitter (clear speech or 16 kb/s data)
- Wideband select
- Power input
- Audio from receiver
- Ground
- PTT or 4 kb/s data
- Squelch or CTS output
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The MA-4777/B is adapted for use in combination with legacy Larkspur
equipment. It can be recognised by the 7-pin Larkspur-style 105 female audio socket
at the front panel. Although this socket is nearly identical to the Clansman one,
it has different index notches at its rim. Note that the internals of the MA-4777/B
are customised to cope with the Larkspur signal levels. On this version, the audio
socket at the front panel is wired as follows:
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- Mic in or Fixed Level Audio (FLA) program input
- Power out
- PTT or 4 kb/s data or key fill data
- Ground
- -
- Audio out
- -
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The C-version of the MA-4777 is made especially for equipment that has
an American style 5 or 6 pin audio socket, often referred to as
U-229. Again, the internals have been customised
to cope with the commonly used audio levels. The wiring of the 5 or 6-pin
U-229 socket (U-283/U) at the front panel of the MA-4777/C is as follows:
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- Ground
- Audio out
- PTT or 4 kb/s data or key fill data
- Mic in or Fixed Level Audio (FLA) program input
- -
- Power out
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- Jane's Military Communications, MA-4777 Digital Speech Encryption Unit
Fifteenth Edition 1994-1995. p. 547.
- Jane's Military Communications, AN/CSZ-6 Vinson-compatible Hand-held Transceiver
Fifteenth Edition 1994-1995. p. 551.
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© Crypto Museum. Created: Wednesday 14 August 2013. Last changed: Sunday, 27 September 2020 - 09:49 CET.
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