What facilities are present in GSM handsets to counter theft and cloning?
GSM mobile phones use a Subscriber Identity Module (SIM) rather than coding the phone number into the actual phone. This means that the phone’s number will change depending on the card. Both the mobile and SIM are validated before a call is set up. Therefore if the mobile is reported stolen it may not work even with a valid card; and if a SIM is reported stolen it won’t work in another handset. GSM is usually encrypted on the air-interface. Robin Fairburns writes: The security applies to the air path between the mobile and the base station … and it’s not as strong as they would like you to believe — someone with the sorts of resources that GCHQ has can crack it in some modest number of minutes. If you think about it for a moment or two, you’ll realise that the only way you could have an encrypted path right the way to the receiving telephone would be if that had decryption capability. On the whole, I would prefer a mobile that let me call anyone to one that was “in principle” totall
