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
