You are trying to book theatre tickets online with a rarely used credit card. Prompted to give a password, you find you can no longer remember it. The result is a failed transaction and a minor rise in blood pressure. It gets worse. While shopping later on, you drop your car keys. An opportunist picks them up and wanders around the shopping mall's car park pressing the unlock button until your vehicle lights flash on. The result is a stolen car and a major rise in blood pressure. Nor are you alone. Electronic security has become a headache for millions of people as they struggle to keep their systems and devices secure – though one leading expert believes he has found a solution. According to Frank Stajano, reader in security at Cambridge University's computer laboratory, each of us needs an electronic aura, a field that would extend no more than two or three feet from our bodies and which could be generated in a similar way to a Wi-Fi signal, only over a very short distance.