Ellinor Millshas an interesting interview with German security expert Karsten Nohl, who showed at the Chaos Communication Congress how easy is to eavesdrop GSM calls. Nohl says that GSM’s A5/1 encryption function uses a 64-bit key that is too short to withstand the computing power available today. When the algorithm was designed 20 years ago when CPU [central processing unit] cycles and storage were much more expensive, it must have seemed a lot more secure. However, the A5/1 function should have been replaced years ago when researchers first discussed practical attacks.
Is there hope? Yes, but not for the time beeing. The GSM opearators have to switch to A5/3. A much stronger algorithm which for the time beeing is secure.
My comment: Do not say things over your mobile phone that you do not want someone to hear.