|
|
|
|
|
|
TSEC/KY-71D -
Wanted item
STU-II/B was a secure telephone unit,
designed by the NSA,
for use by NATO
forces and governments of friendly nations. The design
was based on third generation STU-III (not STU-II)
crypto phones.
It was introduced in the early 1990's to replace the ageing and bulky
STU-II,
It was interoperable with the STU-II (KY-71),
Spendex 40
and other compatible equipment
[1].
Like its predecessor, it uses the SAVILLE cryptographic algorithm,
developed by GCHQ
and the NSA.
|
An example of a STU-II/B phone is the Motorola STU-II/B SECTEL
that is based on the Motorola SECTEL range
of STU-III phones. At first glance, the phone is nearly
identical to, say, a SECTEL 2500, but there are some significant differences.
It is also compatible with
the Philips Spendex 40.
The image on the right was taken from the user manual of the
SECTEL STU-II/B [1].
It shows an extension to standard keypad of the Motorola range of SECTEL phones.
The extra keys are for AUTOVON/IVSN operation only (see below).
|
|
|
First of all, the STU-II/B has 4 additional keys on the keypad (see below).
Secondly, the cryptographic keys are loaded into the STU-II/B by means
of a NATO-standard fill device, such as the KYK-13
or the KOI-18.
For this purpose, the unit is fitted with a U-229 connector at the rear.
All keys are loaded this way, rather than with the KSD-64 key storage device.
The KSD-64 is used here only as a Crypto Ignition Key (CIK).
|
Compared to the SECTEL STU-III phones, the STU-II/B has four additional
keys. They are located to the right of the existing numerical keypad and
are present for backward compatibility with the non-secure
AUTOVON
and IVSN
systems. AUTOVON (Automatic Voice Network) was a military phone system that was
built in the US in 1963. It was designed to survive nuclear attacks [3]
and allowed non-secure voice calls with precedence (piority override).
IVSN was the Initial Voice Switched Network developed by NATO
in the mid-1970s for unclassified voice calls. Starting with 4 switches in
Europe in 1980, the system grew to 24 switches at the peak of its use in the
mid-1980s. When it was closed down on 30 November 2005 [4]
it still consisted of 18 switches, some of which are still in use today.
|
- FO - Flash override
- F - Flash
- I - Immediate
- P - Priority
|
The four extra keys generate DTMF-signals in the rarely used
1633Hz column. On some later keyboards, these keys are sometimes called
A, B, C and D.
After a nuclear attack, it would be very difficult for government officials
to obtain a free telephone line, as nearly everyone would try to make a
phone call.
By pressing the letter P, the user would signal the switch
to appoint a free line by priority. Higher ranking officials were allowed
to press I (Immediate) to get an even higher priority.
Military users were allowed to press F (Flash) in order to get a free
line nearly instantly.
It was thought that only the president and his circle were allowed to
use FO (Flash Override) to give them the highest possible priority.
|
The drawing on the right shows the rear panel of the STU-II/B telephone.
To the right of the power connector is a US Army/NATO-standard 5-pin
U-229 socket (U-183/B) that allows the connection of a
KYK-13 or similar.
Two FILL procedures are possible: NET FILL and UNIQUE FILL (KDC Mode).
Up to 17 net variables and 1 unique key can be stored inside the STU-II/B.
When using the unique key, a valid telephone number of a Key Distribution
Center (KDC) have have been entered first.
|
|
|
The STU-II/B supports the (older) DS-102 standard for key loading.
The pinout of the U229 connector is specified in the table below.
Before loading a key, the STU-II/B first has to be put in the appropriate
mode. Then the key filler
must be attached and activated. If a suitable
key has not been sent by the key filler within 10 seconds, the operation
has failed and all existing keys will be destroyed. This is done as
an extra safety measure against tampering [1].
|
|
Pin
|
DS-102
|
Description
|
|
|
|
|
A
|
GND
|
Ground (common wire)
|
|
|
B
|
-
|
Not used
|
|
|
C
|
ACK
|
FILL request acknowlegment
|
|
|
D
|
DATA
|
Fill data into STU-II/B
|
|
|
E
|
CLK
|
Fill clock into STU-II/B
|
|
|
F
|
-
|
-
|
|
|
For secure operation, a STU-II/B must be unlocked by inserting and activating
a KSD-64A Key Storage Device. With the STU-II/B, the
KSD-64A is only used as a Crypto Ignition Key (CIK) and not as a key
fill device.
The KSD is entered into a so-called keyceptacle at the
right of the SECTEL unit, just below the display. Once inserted,
it needs to be rotated 1/4 clockwise, in order to unlock the
secure features of the phone.
 More about the KSD-64
|
|
|
The STU-II/B supports the following CIKs:
|
- Master CIK
Only one Master CIK can be created for each STU-II/B terminal. The Master
CIK is unique to this particular terminal. This key is normally used and
controlled by the Communications Security (COMSEC) custodian.
It allows Interoperable CIKs (see below) to be added to the terminal
after the fill procedure is complete. It also allows the speakerphone feature
to be enabled or disabled.
- Interoperable CIK
This CIK is to be used by a typical user. 'Interoperable' means that the user
can access up to 7 terminals with one CIK. The CIK data is stored in fields
2 thru 8 of the interoperable CIK.
|
The STU-II/B has three modes of operation, each with a varying degree of
security. The required mode of operation can be selected by pressing the
MODE key until the display shows the correct mode.
A responding STU-II/B will follow this setting automatically.
|
- KDC mode
KDC mode requires the availability of a so-called Key Distribution Center (KDC)
and offers the highest level of security. In this mode, the user first places
a call to the KDC to obtain a so-called KDC Message before completing a
call to another STU-II/B.
The KDC Message contains the per-call keying variable
that allows the user to setup a secure call with one specific terminal.
The STU-II/B can store KDC messages for up to 21 terminals. This mode supports
full-duplex voice calls and data communication up to 9600 baud and half-duplex
voice and data communication at 2400 baud.
- Net mode (Net Point-to-Point)
This mode allows secure communication with another STU-II, STU-II/B or
compatible device, which has the same Net keying material.
The SECTEL STU-II/B can store 17 Net variables. This mode supports
full-duplex voice calls and data communication up to 9600 baud and half-duplex
voice and data communication at 2400 baud.
- Multipoint (Net Broadcast)
This mode is used to broadcast secure voice and data to multiple users.
It is one means of establishing a conference call. Multipoint communication is
possible between multiple STU-II and STU-II/B terminals, provided they are
loaded with the same Net keying material.
In this mode, voice communication is possible in half-duplex only.
Data can be transferred in synchronous half-duplex mode at 2400 baud only.
|
As far as we currently known, the STU-II/B is interoperable with the following
devices:
|
Below, some specific expressions featured on this page are explaned.
For more descriptions, please visit the special
Crypto Glossary,
or follow the links below.
|
|
AUTOVON
|
|
Automatic Voice Network
Military phone system that was built in the US in 1963.
Designed to survive nuclear attacks, it allowed non-secure voice calls with precedence (piority override).
(Wikipedia)
|
|
CIK
|
|
Crypto Ignition Key
A physical token (usually an electronic device) used to store, transport
and activate the cryptographic keys of electronic cipher machines.
(Wikipedia)
|
|
DTMF
|
|
Dual Tone Multy-Frequency
In-band tone system used for telecommunication signalling over analog telephone
lines. The system uses 8 different tones, two of which are sent simultaneously. It is mainly used in push-button phones to produce the numbers 0-9 plus '*" and
'#'. Some keypads are capable of sending A, B, C and D as well.
(Wikipedia)
|
|
IVSN
|
|
Initial Voice Switched Network
Analog switched telephone network developed by NATO in the mid-1970s.
It was used for unclassified voice calls throughout NATO and was discontinued
in 2005.
(More...)
|
|
NATO
|
|
North Atlantic Treaty Organization
(Wikipedia)
(Website)
|
|
|
|
Any links shown in red are currently unavailable.
If you like this website, why not make a donation?
© Copyright 2009-2013, Paul Reuvers & Marc Simons. Last changed: Saturday, 01 March 2014 - 10:01 CET
|
 |
|
|
