QKD – Quantum key distribution is the magic part of quantum cryptography. Every other part of this new cryptography mechanism remains the same as in standard cryptography techniques currently used.
By using quantum particles which behave under rules of quantum mechanics, keys can be generated and distributed to receiver side in completely safe way. Quantum mechanics principle, which describes the base rule protecting the exchange of keys, is Heisenberg’s Uncertainty Principle.
Heisenberg’s Uncertainty Principle states that it is impossible to measure both speed and current position of quantum particles at the same time. It furthermore states that the state of observed particle will change if and when measured. This fairly negative axiom which says that measurement couldn’t be done without perturbing the system is used in positive way by quantum key distribution.