But the practical use...
relies on a secure communication between Alice and Bob in order to exchange K. If one assumes Eve can hear everything Bob can, then Eve would be as efficient as Bob in decrypting P. And if you have a secure means of exchanging a fresh K for every P, then when not use that means for transmitting P? Or do you train Alice and Bob in isolation, then effectively lock K at some point in the future before you separate Alice and Bob?
Biting the hand that feeds IT
