 The security of encryption that uses quantum key distribution relies on the foundations of quantum mechanics, in contrast to traditional public key cryptography, which relies on the computational difficulty of certain mathematical functions, and cannot provide any mathematical proof as to the actual complexity of reversing the one-way functions used.QKD has provable security based on information theory, and forward secrecy.The main drawback of Quantum Key Distribution is that it usually relies on having an authenticated classical channel of communications.