GSMK CryptoPhone G10 User manual

CryptoPhone G10 User Manual
GSMK G10 - Release 1.2 PTT
GSMK
CryptoPhone G10
User Manual
Contact
For support, service and repair please contact:
e-mail: [e-mail]
phone: +49 700 CRYPTTEL
fax: +49 700 CRYPTFAX
Further information: http://www.cryptophone.com
© 2005
Gesellschaft für Sichere Mobile Kommunikation mbH
(GSMK), Berlin, Germany
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28

General 3
Inserting SIM card & switching the phone on 3
Enter your PIN 4
Charging 4
Standby 6
Flight Mode 6
Placing an Encrypted Call 7
Key Verification 8
Call Quality during Secure Calls 9
Switching the Calltype 10
Problems with setting up a Secure Call 11
Changing the volume 13
Mute during call 14
Secure Push to Talk 14
Secure Calls while moving 15
Redialing 16
Calling from the Contacts list 16
General Mobile Phone Security Advice 17
Power down 17
Cold Boot & Emergency Erase 17
Security Advice regarding Flash Memory 19
Using the headset 20
Bluetooth headset 20
Sync Contacts and Appointments 21
Troubleshooting 22
Security Updates 22
Security, Storage and Handling 24
Repairs 25
Accessories 26
3rd Party Software 27
Contact 28
CryptoPhone G10 User Manual
2
3rd Party Software
In theory it is possible to install Microsoft Smartphone
compatible 3rd party software on your GSMK Crypto-
Phone device. You should know that 3rd party software
of any kind can be used to attack the integrity and secu-
rity of your GSMK CryptoPhone. Installing additional
software on Communication Security equipment like
the CryptoPhone is a grave security risk that you should
only take if it is absolutely necessary. Please be aware
that installing 3rd party software might irrevocably
compromise the security of your CryptoPhone or dam-
age its functionality.
GSMK does not provide any support for installing 3rd
party software and will not provide support for prob-
lems caused by installing 3rd party software. Any and
all problems caused by 3rd party software are not cov-
ered by warranty or support.
You have been warned.
If you require large number of custom CryptoPhones
that include certain software components of your
choice by default, please contact [e-mail]
to discuss your requirements.
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27

General
Your CryptoPhone G10 is based on a generic tri-band
(900/1800/1900) GSM Smartphone that is sold under
different brand names. The phones firmware and op-
erating system have been modified to accommodate
the CryptoPhone functionality and provide added secu-
rity, so a number of things that you might know from
other Smartphones are not available on the GSMK
CryptoPhone for security reasons. We supply the origi-
nal Smartphone manuals, license sticker and CD with
the GSMK CryptoPhone G10, but you need to be aware
that some functionality has been disabled by us for
security reasons. Do not try to use Microsoft operating
system updates as this may destroy the CryptoPhone
firmware and void your warranty. Certified Crypto-
Phone Updates are only provided by GSMK to you in a
cryptographically secure manner.
Inserting SIM card & switching the
phone on
You need to insert a valid GSM card (SIM) in the
GSMK CryptoPhone G10 in order to place calls. To
insert the SIM, remove the back cover of the device by
pressing the latch on the lower backside and sliding the
cover downwards. You will see the SIM card slot in the
lower corner of the device. Lift up the SIM card cover
CryptoPhone G10 User Manual
3
There is no such thing as a »restocked«, »refurbished«
or »second hand« CryptoPhone. All sales are final. If
your CryptoPhone is defective, we will either repair it or
swap the electronics for a new factory fresh device. No
parts that have been in the hands of other customers
will be used in repairs. If you need a repair, please mail
us at [e-mail], so we can instruct you
about the proper shipping and security procedures.
Shipments that arrive for repair without prior acknowl-
edgment and/or in ignorance of the advised shipping
method and security precautions will be ignored.
Please understand that it is in your own interest to ad-
here to the security measures, since only this will en-
able us to fulfill your security requirements. Note: the
high-power Lithium-Polymer rechargeable battery of
the CryptoPhone is a wear-and-tear part and not cov-
ered by the warranty. Replacement batteries are avail-
able in normal PDA or mobile phone stores.
Accessories
The GSMK CryptoPhone is based on a device manu-
factured by HTC, sold under different brand names.
Additional accessories for your CryptoPhone (like hol-
sters, car kits, external antennas etc.) can therefore be
easily obtained by buying kit that is destined for SDA, i-
mate SP3i or Qtek 8020 devices.
CryptoPhone G10 User Manual
26

by pushing it in the direction marked “Open” and in-
sert the SIM. Then click the SIM card cover down so
that it is firmly closed. Now insert the battery (which is
stored stored separately in the shipping box).
Replace the back cover by sliding it gently upwards
onto the device. Now push the power button on the top
of the device. The screen will light up and the GSMK
CryptoPhone G10 begins its firmware initialization.
This may take up to two minutes.
Enter your PIN
Most GSM SIM cards require you to enter a PIN num-
ber. After you have switched on the CryptoPhone, you
will be asked to enter your PIN. After you entered the
PIN, press the “Done” button. The CryptoPhone will
finish initialization and provide the secure telephony
mode. If your GSM SIM does not require a PIN, the
secure telephony mode will be enabled right away. We
recommend that a PIN number is used to enhance
individual security.
Charging
Before using your CryptoPhone, we recommend that
you charge the battery until full. In order to do this, you
must connect the power supply to the CryptoPhone.
Depending on your location, you may need a plug
CryptoPhone G10 User Manual
4
sive scientific effort (several months of analysis at the
cost of several 100.000 Euros per device). If in doubt
and your security depends on it, consider purchasing a
fresh unit.
The CryptoPhone is specified and designed for use in
normal business, home and other general conditions.
It is not reinforced or specially sealed against water and
other harsh environmental conditions. (For reinforced
versions of the CryptoPhone that comply with military
specifications, contact us at [e-mail]).
Submitting the CryptoPhone to excessively high or low
temperatures (like in the outside pocket of an overcoat
in cold climates) might temporarily or permanently
damage the display and lead to accelerated battery ag-
ing, affecting the ability of the battery to store power
and thereby reducing the standby time of your Crypto-
Phone. Sitting on the CryptoPhone or submitting the
device to other heavy mechanical loads may damage
parts of the phone, especially the keyboard. Damage to
the keyboard, battery and display as well as any kind of
other mechanical damage is not covered by the war-
ranty.
Repairs
Because of the manipulation risk, we do not take back
any CryptoPhones from customers, except for repairs.
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25

adaptor to use the power supply if the plug does not fit
in your outlet. The power supply is rated 100-240V,
which means it will accept your line voltage without
conversion as long as it lies within this range. The LED
in the upper area of your CryptoPhone will change
color to yellow while the device is being charged, and to
green when fully charged. You can either charge the
CryptoPhone with the power supply (recommended)
or with the supplied USB sync cable on a computer.
Charging over USB takes considerably more time and
is dependent on your computers configuration and
setup, so it may not work under some circumstances
(e.g. if you have no synchronization software installed
on your computer or the USB port is not powered up).
Due to the higher power consumption of the built-in
powerful computer and the backlit display, the standby
and talk times in secure mode are less than what you
might expect in normal GSM phones. Also please note
that the standby and talk times may vary depending on
your distance to the nearest GSM base station: the fur-
ther away the base station, the more power your phone
needs to use to reach it. Spare batteries are available in
normal electronic stores that sell mobile phones.
Note: we recommend to charge your GSMK Crypto-
Phone every night or have a charged spare battery
ready. For security reasons explained later in the chap-
CryptoPhone G10 User Manual
5
immediately, as this may be an attempt to insert mali-
cious firmware into your CryptoPhone. Please see our
Questions and Answers section (Q&A) on the website
http://www.cryptophone.com/ for further detailed in-
formation on the benefits of published source cryptog-
raphy.
Security, Storage and Handling
Your CryptoPhone is a Communication Security
(COMSEC) device. It can only be regarded as secure as
long as you have permanent and uninterrupted physi-
cal control over the CryptoPhone. Once an adversary
could have gained temporary physical possession of the
CryptoPhone, it must be regarded as compromised.
There is a variety of potential methods that would allow
an adversary to listen into your calls after he manipu-
lated the CryptoPhone and gave it back to you. Keep the
handset with you securely at all times. Optimally, you
should take it with you to the bathroom, put it beside
your bed when you sleep and not leave it alone in the
hotel room.
If you have »lost« the CryptoPhone and »find« it back
again, it has to be regarded as compromised. Never
lend your CryptoPhone. Major intelligence agencies are
known for a wide variety of high-tech manipulation
methods that are impossible to detect without a mas-
CryptoPhone G10 User Manual
24

ter ‘Security, Storage and Handling’, we suggest you
keep the CryptoPhone with you at all times so that it is
under your permanent supervision. If the phone rings
or you need to place a call while the phone is charging,
you can leave it plugged in while operating the phone.
Standby
The GSMK CryptoPhone has four basic modes of op-
eration. It can be either completely switched off, in
‘standby mode’, active, or in ‘flight mode’. In normal
operation the CryptoPhone is in ‘standby mode’. In
standby mode, you can switch the device on at any time
by briefly pressing the left button right below the dis-
play and disabling the key lock.
Now the screen will light up. To put the GSMK Cryp-
toPhone G10 back in standby mode, simply wait until
the the screen goes dark. The GSMK CryptoPhone will
still receive incoming calls when it is in Standby mode.
In other words: standby mode will not disable the radio.
Flight Mode
It is not safe to enter an airplane, hospital or other no-
phone area with the GSMK CryptoPhone switched on
or in standby mode. To ensure the radio is off, you
need to enter ‘flight mode’. To enter flight mode, press
the On/Off button briefly and select “Flight Mode” in
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6
new attack methods. Since the CryptoPhone comes
with full published source code, the chances are much
higher for a flaw to be discovered and fixed quickly than
with any closed-source cryptographic product. Our ad-
visory board of distinguished cryptographers and secu-
rity researchers help us to identify and counter poten-
tial threats based on their intimate knowledge of the
latest academic research and emerging cryptanalysis
methods. In case a firmware update is needed for secu-
rity reasons, you will get notified either via the e-mail
address that you supplied when purchasing the Cryp-
toPhone online, or directly by the distributor.
If you receive a notice about an upcoming security up-
date, please verify it directly at our website
http://www.cryptophone.com/ to prevent attackers
from slipping you a malicious »update«. Please note
that we will describe the details of the update procedure
directly on the website.
The firmware update mechanism is cryptographically
secured using a 4096 bit public key signature system,
which ensures only signed CryptoPhone updates will
be accepted by your CryptoPhone.
If you receive suspicious communication regarding
CryptoPhone updates (such as an unannounced e-mail
with an update file as attachment), please inform us
CryptoPhone G10 User Manual
23

the list by pressing the 2 key. You will now see a little x
next to the antenna symbol when flight mode is active
and the GSM is switched off. To switch the radio back
on again, follow the same procedure and select “Flight
Mode Off”. You will be required to enter your PIN
again.
Placing an Encrypted Call
In order to place a secure call, the following conditions
need to be met:
•your partner has a CryptoPhone compatible device
up and running
•there is sufficient GSM coverage
•the GSM operator supports ‘GSM data calls’
(technically called Circuit Switched Data or ‘CSD’)
To place a secure call, you can simply dial from the
home screen and press the “Call Secure” softkey on the
left side. Also you can choose “Contacts”, select a con-
tact and press “Call Secure”. Further you can switch to
the CryptoPhone screen by pressing the home key and
dial directly (press the green Call button after entering
the number.
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7
Troubleshooting
In the event that the Cryptophone reacts unexpectedly
i.e., device response becomes very slow, key-lock can
not be unlocked, or the phone does not connect to a
GSM network, you can quickly reset it by removing
and re-inserting the battery. The GSMK CryptoPhone
will restart without erasing the memory. In the unlikely
event such a problem persists, you can Cold Boot the
device (see page 16). This will however delete all infor-
mation in volatile memory.
Security Updates
GSMK continually seeks to improve the security and
quality of operation of the Cryptophone G10. In the
event anyone discovers a flaw in the CryptoPhone, we
will provide a firmware update, as well as a detailed
report on the possible security impact. As bad as secu-
rity problems with cryptographic products can be, we
believe the only way to handle them properly is open
and transparent communication with our customers.
You are the one best suited to determine potential
damage to your interests, so we will provide you with all
the known facts.
Security is not a state but a process. And this process
requires constant checking against emerging risks and
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22

You will hear a bit of comfort noise in the speaker, fol-
lowed by the normal ringing tone. It may take a bit
longer than normal before the connection is made, so
please let it ring. After your partner has pressed the
Talk button on his end, you will hear a ditt-dutt ditt-dutt
sound that signals to you that the ‘key setup’ procedure
for the secure connection is in progress. Key setup may
take from 3 to 30 seconds, but typically 8 seconds, de-
pending on line quality. Once key setup is completed
you hear a »Ping« sound and can start talking to your
partner. In order to verify the authenticity of the key,
Please take a look at the display and read the three let-
ters under »you say« to your partner and verify the
three letters under »partner says«. The green SECURE
indicator is only visible when a secure call is estab-
lished. During all other times it is shown in grey with a
open lock.
Key Verification
Reading the three letters and verifying what your part-
ner says is meant to protect you against so-called ‘man-
in-the-middle attacks’ on the secret session key. The
letters are mathematically derived from the unique se-
cret key that is used during each call. By reading and
CryptoPhone G10 User Manual
8
CTQ DGA
Sync Contacts and
Appointments
The CryptoPhone supports in principle the sync of con-
tact and calendar entries with a computer. You need to
be aware that in theory it might be possible to attack the
operating system of the CryptoPhone by supplying
manipulated data to your PC or exploiting unknown
problems in ActiveSync. GSMK does not recommend
to sync your CryptoPhone with a PC, especially if the
PC is connected to a network, for security reasons. If
you have high security demands and need to calculate
with a very sophisticated adversary, avoid to sync your
CryptoPhone with a PC. The CryptoPhone ships with
de-activated Active Sync functionality. You need to re-
activate the sync option manually in the CryptoPhone
to use it. To initiate a sync, connect the CryptoPhone
with the computer using the enclosed USB cable.
Note: Sync over IrDa (Infrared) and Bluetooth has been
disabled on the CryptoPhone as a precautionary secu-
rity measure. While we are currently not aware of ac-
tual problems with these sync options, there is a very
strong likelihood that such problems will arise in the
future. The main risk is that an adversary could poten-
tially gain wireless access to your device while it is in
your pocket or just on the desk in front of you.
CryptoPhone G10 User Manual
21

verifying them with your partner, you make sure that
you are indeed communicating using the same key.
Please pay attention to the voice of your partner when
he reads his three letters. To be completely on the safe
side against very sophisticated voice impersonation
during the key verification, you could periodically rever-
ify the letter code with your partner during the conver-
sation.
Call Quality during Secure Calls
The call delay indicator changes color in five steps be-
tween green over yellow to red. Green indicates the best
call quality, red the worst. Delay describes the period of
time it takes for your voice to reach your partner. This
time gets longer if the transmission of the encrypted
voice over the telephone network takes longer, or
transmission errors occur.
Reasons for longer than normal delay are usually either
bad GSM coverage or network congestion. Network
congestion can often be circumvented by setting up the
call again, sometimes you just get a »bad line«. The
GSM data call mode, used by the CryptoPhone to
transport the encrypted voice data during a call, has a
certain delay, caused by the architecture of the GSM
network. The GSM network handles data with lower
priority than voice transmissions.
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9
Using the headset
For hands free operation, a stereo headset is included
with the GSMK CryptoPhone. You can plug it in any
time, before or during a call, however you may termi-
nate an ongoing call under some conditions when in-
serting the headset plug off-angle. The headset cable
connector socket is on the lower right side of the device.
GSMK does not provide support for problems caused
by using headsets other than the one supplied with
your CryptoPhone.
Bluetooth headset
The CryptoPhone G10 has a Bluetooth interface. While
it is possible to use a Bluetooth headset for making
normal unencrypted phone calls, we strongly not rec-
ommend using a bluetooth headset during encrypted
calls. The reason is that with a Bluetooth headset you
would broadcast the contents of your confidential calls
before they have reached the encryption engine in the
CryptoPhone. Bluetooth radio signals can be received
over several hundred meters with moderately sophisti-
cated equipment, so an attacker could listen to your
calls easily. The encryption used with Bluetooth is no
hurdle for a determined adversary and does not offer
sufficient protection. We recommend using a wire
based headset when placing secure calls.
CryptoPhone G10 User Manual
20

So even if the delay indicator is green, there is always a
certain noticeable delay, much like on some transcon-
tinental phone calls. If the overall line quality becomes
bad, the delay rises and you may experience »drop
outs«. Note that the quality on international calls might
not be as good as on domestic calls. The multiple op-
erators involved in an international call often try to
minimize their costs by technical measures that can
affect the quality of the call. If the call quality is unac-
ceptable, please try calling again. Call quality can also be
adversely affected when using certain GSM providers.
If the Delay indicator becomes reddish or red, please
try to find a place with better GSM coverage. Use the
signal strength indicator on the right upper side of the
display to find a better spot. If the delay indicator turns
and stays solid red, please hang up and set up the call
again. When no call is in progress, the delay indicator is
shown grey.
Switching the Calltype
Normally, the CryptoPhone uses the V.110 circuit
switched data (CSD) - also called digital data call -
bearer type to establish a secure connection. To call to
an analog landline or to a CryptoPhone on a satellite
network or a network with weird data-call configuration
CryptoPhone G10 User Manual
10
Security Advice regarding Flash Mem-
ory
With the GSMK CryptoPhone, various information is
stored in Flash Memory. Flash type storage is safe
against failure of the backup-battery. You must how-
ever be aware that there is no way to securely erase in-
formation stored in flash memory in a way that it can-
not be possibly reconstructed by sophisticated methods
of computer forensics. Even if you erase the informa-
tion and overwrite it with other data, it cannot be con-
sidered safely destroyed when stored on Flash Mem-
ory. Flash memory uses its own way of managing files
that is beyond the control of the operating system.
So files that are no longer visible after deletion in the
file manager may still exist in some unused part of the
Flash memory. In addition, esoteric physical effects
( " memory burn in ") make it possible for a forensic in-
telligence laboratory to reconstruct the former content
of Flash memory, even if it has been erased or overwrit-
ten once. The same problem holds true for (mini)SD
memory cards, because they are also based on flash
memory technology. We therefore recommend that
any potentially compromising information is not stored
in the Flash Storage if there is a risk that the device may
fall into the wrong hands.
CryptoPhone G10 User Manual
19

(like most GSM carriers in the USA), you can switch to
the V.32 bearer mode.
To switch the calltype, go the home screen, press the
Start softkey and then More --> More --> Configura-
tions --> CSD Line Type (you can also type the keys
Start --> 9942 to get there, under most circumstances) .
You will get to the configuration menu for CSD data
call settings. Now switch the entry under “Data rate” to
“9600 bps(V.32). Press the OK softkey. Switch the
phone off and on again. To switch back to V.110, use
the same menu to change the “Data rate” entry to
“9600 bps(V.110)”, press OK and restart the phone by
switching it off and on again.
A small desktop phone icon in the CryptoPhone screen
will show up if V.32 is activated. The call setup with
V.32 takes longer then with V.110, as the modems need
some time to synchronize. Incoming calls are not af-
fected by the call type settings.
Problems with setting up
a Secure Call
Some providers restrict the reception of GSM data calls,
such as needed for the CryptoPhone. The practice is
becoming increasingly rare, but a GSM-provider may
only allow incoming data calls to subscribers that have
CryptoPhone G10 User Manual
11
sary. Cold Boot will not erase the contacts and SMS
messages stored on your SIM card. Also, a Cold Boot
does not erase any information that you may have
stored in Flash (Storage) or on SD memory cards.
To initiate a Cold Boot follow the following procedure:,
1. remove the battery, re-insert the battery,
2. place the phone on a flat surface
3. hold the softkeys (1) and (2) while pressing briefly
the power button (1 sec)
4. wait till the screen becomes dark, then release the
softkeys simultaneously
5. press 0
Now the re-initialization process takes place and the
phone will boot up again after a while.
Note: no key material that might compromise the secu-
rity of your past calls is stored anywhere on your device.
Upon completion of a secure call, all key material for
the call is destroyed and permanently erased. The rec-
ommendation for a Cold Boot in emergency situations
only relates to other data stored on the device like notes,
contacts, SMS, call history etc.
CryptoPhone G10 User Manual
18

a special ‘data subscription’, which comes with a special
second phone number to call to reach the Crypto-
Phone. Some providers may not recognize that a num-
ber you are calling is a GSM/ISDN number, and erro-
neously try to handle the call via a modem. This can be
recognized by the called party because he/she hears a
modem sound when picking up the phone. Some pro-
viders may not pass data calls to certain other providers
at all.
Under certain circumstances, especially when roaming
in GSM networks that are not properly configured, the
“never ending key setup” problem may occur. The
phenomenon is that the key setup phase takes longer
then 20 seconds and never comes to an end. The un-
derlying technical problem resides in the GSM net-
work. Data calls are sometimes set up but then fail to
transport any data.
All of the above conditions may make it impossible to
use the CryptoPhone in one or both directions between
two CryptoPhones. To by-pass this problem if you are
roaming try switching providers. If secure calling only
works in one direction, you could use an unencrypted
call to tell the other party to call you using Crypto-
Phone. These problems are inherent to using the CSD
data call facility and apply to all encrypted telephony
over GSM.
CryptoPhone G10 User Manual
12
General Mobile Phone Security Advice
The use of mobile phones and other radio transmis-
sion equipment in certain areas is prohibited or re-
stricted. Because of the risk of interference with life-
support equipment, the use of mobile phones is also
banned in most hospitals. Using a mobile phone in an
airplane is a felony in most countries. You are respon-
sible for complying with local laws and regulations.
Power down
Simply press the power button for three seconds and
the phone switches off. The GSMK CryptoPhone
firmware is unaffected by a power-down as it resides in
non-volatile memory. It is recommended to store the
CryptoPhone with the battery removed if it is not used
for prolonged periods of time (e.g. several weeks).
Cold Boot &
Emergency Erase
Initiating a Cold Boot is recommended in emergency
situations, to erase data stored in volatile memory that
might compromise your security (like SMS, call his-
tory, notes, appointments etc.). Please note that this is
not a very secure erasure procedure. Traces of your data
might be reconstructed in memory by a skilled adver-
CryptoPhone G10 User Manual
17

For customers in Europe, North Africa and Asia who
experience such problems we recommend our Crypto-
Phone 200 T/TS solution that uses the Thuraya satel-
lite system to provide the added benefit of affordable
secure communication outside GSM covered areas.
Sometimes a specific condition of the GSM network
may lead to an unstable state of the GSM part of the
CryptoPhone, which also might cause the “never end-
ing key setup”-problem or other undesired behavior.
This condition can sometimes be fixed by restarting the
CryptoPhone.
Changing the volume
To change the audio volume during a Secure Call, use
the volume control buttons on the left side of the de-
vice. A volume indicator is located in the lower left cor-
ner of the screen and will provide you with visual feed-
back regarding the volume you set. Please not that the
volume levels above green on the indicator (yellow, red)
are only designed to be used with a headset or the Push
to Talk mode. Chosing them while not using a headset
or Push to Talk may lead to distortions and feedback
effects that can reduce your call quality considerably.
CryptoPhone G10 User Manual
13
Note: In many countries the use of mobile phones
while driving is regulated or completely prohibited. You
are responsible for complying with local laws and
regulations on telephone use while driving a car. We
strongly recommend the use of the enclosed headset
while driving, even if local regulations may not require
this.
Redialing
The CryptoPhone has access to a call history compris-
ing the last 10 outgoing calls.. You can redial a number
by scrolling through the last dialed numbers by moving
the joystick up/down and press the green Talk button
once the desired number is shown in the display.
Calling from the Contacts list
To call a contact stored in the contact list, press the right
soft key in the home screen labeled Contacts. Now you
see the list of contacts stored on your SIM and on the
phone. The left softkey is now labeled Call Secure. To
place the secure call, move the selection bar with the
joystick to the contact and press the Call Secure key.
The CryptoPhone G10 now switches to the secure call
mode and immediately dials the selected contact num-
ber in secure mode.
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16

Mute during call
To mute the microphone during a call, press the soft-
key labeled “Mute”. To switch the microphone back on
again, press the “Mute” key again. The current status is
shown in the display with the Mute/Unmute Icon.
Secure Push to Talk
In certain situations, especially when you have a lot of
background noise or need a high speaker volume, you
can activate the Push to Talk mode (or PTT for short),
to achieve good call results. This can be done either
during a Secure Call or before. To activate or deactivate
PTT, press the “Menu” Softkey, choose “Push to Talk”
in the Settings screen, toggle the setting with the center
click and press the Done softkey to return to the main
screen. PTT works like a two-way radio. When you
want to talk, you press the PTT button. When you fin-
shed speaking, you release the button. The button used
for PTT on your CryptoPhone G10 is the Camera but-
ton on the right side of the device. Please do not forget
to release the talk button when you finished talking.
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14
Secure Calls while moving
When using the GSMK CryptoPhone while moving
fast in a car or a train, you may experience a degrada-
tion in call sound quality, periods of longer delay and
short dropouts during a call. These effects are the result
of a so called handover that occurs when you move
from the coverage zone of one GSM tower (also called
'GSM cell') to the next. During the handover the data
connection is briefly interrupted. To prevent important
call contents from getting lost, the GSMK Crypto-
Phone, unlike other encrypted voice systems, acceler-
ates the speed of decoding for a moment after the
dropout, to catch up with the lost transmission time.
This results in the voice of your partner rising in pitch
(the »Mickey Mouse effect«) for a moment. After a
short time the pitch returns to normal. The GSMK
CryptoPhone G10 has been successfully tested travel-
ing at speeds of up to 180km/h. The frequency and
intensity of disturbances is primarily determined by the
GSM network. In rural areas, the network consists of
fewer and bigger cells, resulting in less frequent han-
dovers and less disturbances. In urban areas the net-
work has typically a high density of small cells, result-
ing in many handovers when moving and thereby
causing more disturbances.
CryptoPhone G10 User Manual
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