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← USA Phone DES
Secure telephone
CVAS III
was a secure telephone with built-in encryption and
decryption, developed around 1988 by A-O Electronics (later: Infosafe
Corporation) in Tucker (Georgia, USA). The device was intended for use by
the US Government and civil customers.
It is equipped with NSA Type 3
cryptographic algorithms
like DES,
AES and SHA, making it suitable
for unclassified but sensitive information.
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The image on the right shows a typical CVAS III phone.
It has a white plastic case, similar to that of an ordinary telephone.
The area with the controls however, is red in order to indicate the
special purpose of this device.
Like most crypto phones, the CVAS III can also be used as an ordinary
telephone. All calls, even secure ones, are initiated in clear mode.
Once both parties have agreed to switch to secure mode, the
SECURE key is pressed. After a 10 to 15 second delay, secure mode is
activated and the conversation can no longer be overheard.
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In order to be able to have a secure conversation, both parties need
to use the same cryptographic key. This can be done in two ways.
As each key has a length of exactly 16 characters, both parties can
use a predetermined key list and type in the same key
(using the SET KEY button).
Alternatively, the phone can generate a fully random key and exhange
this key with the phone at the other end. In that case, all the user
has to do, is press the SECURE button. Both phones then generate
a 4-digit verfication code that should be identical. If it is not
identical, the quality of the telephone line is below average or the
line has been intercepted by a third party.
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As the CVAS III is a Type 3 cryptographic product, it doesn't provide
protection at the highest possible level. As such it is not built to
comply with NSA TEMPEST en EMC requirements. The case is made of plastic
and has no shielding whatsoever.
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After opening the case, two large stacked PCBs are immediately visible.
The are held together tightly by two long connectors;
one at either side of the PCB.
The upper board contains the analog parts, the modem, and the (telephone)
line interface. All lines to the outside world are connected to this board
by means of small brown connectors.
The lower board contains the digital parts, such as the microprocessor, the DSP,
the memory, interfaces and the firmware (in EPROM).
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After separating the boards, it becomes immediately visible what methods were
used in the late 1980s to protect intellectual property. The text of most of
the key components of the phone has been scraped off, so that competitors could
not see which technology was used.
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Audio is sampled by the CVAS III at 64,000 bits per second and then compressed
down to 2400 baud using a Linear Predictive Coding (LPC) algoritm known as PARCOR.
The resulting voice has a slightly synthetic sound, but is still very
recognizable and intelligible [A].
Once the voice is digitized, the digital signal is encrypted using the
Data Encryption Standard (DES) encryption algorithm.
This algorithm, developed by the National Bureau of Standards,
is classified by the NSA as a Type 3 product.
The CVAS III-E version of the phone, uses the proprietary EDAS
ecryption algorithm, but is still interoperable with the earlier CVAS III
models.
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A-O Electronics was established in 1985 in Tucker (Georgia, US),
for development and production of
voice encryption equipment.
Early products, such as the so-called MDSS (Multi-Dimensional Security System)
– introduced in 1987 – used an insecure
frequency inverter (scrambler) for the
protection of voice data [1].
Later systems like the CVAS III-e, used real digital data encryption.
Late 1988 the company was renamed to Infosafe Corporation and shifted
its focus to PC data security. In the meantime, the company had moved to
North Charleston (South Carolina).
In 1992, Infosafe ran into financial trouble and several attempts
were mounted in order rescue the company. Finally, around 1995, the
company closed its doors.
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- A-O Electronics Inc.
2137 Flintstone Drive
Tucker, GA 30084
Phone (0)404-4918044
USA
- AOE International
2137-E Flintstone Drive
Tucker, GA 30084
Phone (0)404-9342244
USA
- Infosafe Corporation
3125 Ashley Phosphate Road
North Charleston, SC 29418
(Charleston County)
USA
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Unfortunately, neither AOE International, nor Infosafe Corporation
exist today. As they closed their doors around 1995, not much can be
found on the internet.
If you have any information about AO Electronics (AOE), Infosafe Corporation
or any of their products, please contact us.
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- AO Electronics Inc., CVAS III Operations Manual
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© Crypto Museum. Created: Wednesday 11 August 2010. Last changed: Sunday, 25 February 2018 - 14:52 CET.
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