Private Mobile Networks, the UK provider of private GSM network technology, has announced support for encrypted handsets from Enigma, Cryptophone and Sectera to support the PMN secure GSM solution.
"The PMN network already provides a level of user access security," explained Chris Moore, sales director for Private Mobile Networks. "We ensure that the network is secure from unwanted parties, since only handsets registered on PMN can utilise network functionality."
The PMN software checks the phones using the IMSI and the IMEI to ensure secure registration of the handset to the network. No one can roam on the network unless previously registered. This database control means that all handsets are checked before accessing the networks.
To ensure that the network is secure when used over multiple networks as well as in the local area, the PMN swaps encryption keys as traffic moves between networks.
Encryption on handsets, when required, uses industry-standard encryption algorithms, A5.1 and 5.2.
A secure call is established by making a data call rather than a standard voice call. This allows the audio to be encrypted without breaking the standard GSM voice compression and ensures proper transmission across different network types. The data call is usually made using the GSM CSD (Circuit Switched Data) services, although some handsets/software make use of the packet switched GPRS/EDGE service instead. Obviously, in the latter case, the PMN system must include the optional GPRS element in order to support such functionality.
Secure handsets which are based on CSD tend to use the same basic elements, namely use of CSD at 9.6 kbps, asynchronous, transparent mode for both mobile originating and mobile terminating calls. In order to support secure handsets, PMN includes support for CSD at an asynchronous rate of 9.6kbps in transparent mode.
Private Mobile eXchange (PMX) is a mobile network switching subsystem, implemented in software, with all the components for switching mobile calls, switching short message service calls, storing and transmitting SMS and providing Packet Data (GPRS and EDGE) in software, complete with translation and routing tables to act as a replacement PBX and/or MSC. PMX is a GSM product - 2G and 2.5G (with packet data optional). The GSM voice calls and SMS are compatible with both 3G and 2G phones and terminals.
PMN solutions are deployed in the UK under the TeleWare low power GSM spectrum licence. Overseas, local low or high power spectrum licences may be required. Changing spectrum frequencies periodically can add an additional level of security to the network.