Cyberspace has become the most popular carrier of information exchange in every corner of our life, which is beneficial for our life in almost all aspects. With the continuous development of science and technology, especially the quantum computer, cyberspace security has become the most critical problem for the Internet in near future. In this paper, we focus on analyzing characteristics of the quantum cryptography and exploring its advantages of it in the future Internet. It is worth noting that we analyze the quantum key distribution (QKD) protocol in the noise-free channel. To include real practical stimulators, there are developed various QKD Schemes for the noisy channels. Here we develop the unconditional security of quantum cryptography theoretically, which is suitable for the Internet as ever-increasing challenges are inevitable in the future.

Quantum key distribution (QKD) uses individual light quanta in quantum superposition states to guarantee unconditional communication security between distant parties. In practice, the achievable distance for QKD has been limited to a few hundred kilometers, due to the channel loss of fibers or terrestrial free space that exponentially reduced the photon rate. Also experimentally it is proved that the Satellite-based QKD promises to establish a global-scale quantum network by exploiting the negligible photon loss and decoherence in the empty space.

In this paper, we also give some introduction to various public-key cryptography and also touch on the various functions, advantages, and disadvantages of quantum cryptography and the need for quantum cryptography in the future as in data encoding, and digital signatures, and many more. It also covers the various securities issue of our current cryptography system. Different protocols BB84 i.e., the first QKD protocol also some other protocols, and finally the future directions of quantum cryptography followed by the conclusion of the paper.