A team of University of Surrey scientists has developed
technology that can deliver end-to-end security and confidentiality
for mobile phone calls.
Many users do not realise that when they use a mobile phone the
wireless part of the link, which is secured by the mobile network
operators, is only between the mobile phone and the base station
closest to the caller and recipient. In between, the signal travels
through ordinary phone lines. At this point it is possible for
conversations to be accessed by unauthorised parties.
Previous attempts to make mobile phone conversations totally secure
have been successful but have relied on a special GSM data service
that has resulted in some operational problems.
In particular, these solutions have required expensive dedicated
handsets and subscriptions, and calls between different countries
can be unreliable. The University of Surrey system is the first
true end-to-end secure GSM system that does not rely on a special
GSM data service.
Encryption techniques are not new, but until now it has been
impossible to use these with mobile phones. Traditional landline
encryption systems convert voice messages directly into digital
data, which is then transmitted.
But current mobile phones have a much lower digital information
transmission capacity than landlines. In order to provide good
speech quality at much reduced digital information rates, mobile
phones assume that the signal to be transmitted is plain speech,
and cannot therefore recognise or transmit the data signals of
encrypted speech.
Scientists at the University of Surrey have overcome this problem
by modulating encrypted speech patterns into audio streams that
both mobile and landline technology will accept.
The University of Surrey said its system is the first of its kind
in the world, and it is being developed by university spin-off
company MulSys for potential users.
Ahmet Kondoz, a professor in the University of Surrey's Centre for
Communication System Research, said, "This is the first true
end-to-end GSM secure voice transmission technology that uses the
GSM voice channel to transmit encrypted speech.
"By using the standard voice channel, it will offer unprecedented
levels of security and quality of service for mobile secure
communications."