Currently, submarines use random “keys” that are known as one-time pads in order to encrypt messages, where each key can only be used once so that it is virtually impossible for eavesdroppers to crack the code. Too bad the key must be securely agreed prior to the submarine’s base departure.
With quantum key distribution (QKD), the quantum properties of photons are taken advantage of, where they are polarized in two different ways in order to encode 0s and 1s, resulting the generation and exchange of a key. Should there be any attempt made to intercept the photons, such properties will be disturbed, raising an alarm in the process.