The demand for secure communications keeps growing. Now three groups have realised the Holy Grail of cryptography. Using quantum mechanics they have sent information with a code that is both unbreakable, and impossible to intercept, as they will report soon in Physical Review Letters . Public key encryption uses large numbers to generate a freely-distributed key which can be used to encode messages.
Messages are very difficult to decode without knowing the original numbers.
Difficult, but not impossible. Quantum cryptography overcomes the weaknesses of both schemes. At its heart is an effect called 'entanglement'. Do something to one photon, and the other is immediately affected. As soon as one of the photons hits either Alice or Bob's detector it is forced to 'choose' an orientation, and its twin simultaneously takes on the opposite orientation.