It's not just dodgy wired phone chargers that you have to worry about -- a poorly-made wireless charging pad could easily toast your phone. But how do you prevent that from happening when there are no cables or ports involved? MIT has an idea. Its researchers have unveiled a security chip that would prevent a wireless charger from topping up your phone unless it authenticates through a cryptographic handshake. It revolves around a smaller, more efficient charging circuit where there's a main coil (for the actual charging) and a secondary coil that can produce a strong magnetic field. If your phone and the charger don't exchange the right public cryptographic keys, that secondary coil will "scramble" the primary coil by changing its frequency.