The distribution of cryptographic keys is one of the primary factors that determine the security and efficacy of a cryptosystem. An otherwise unbreakable cipher, such as the one time pad, can be breached during the key distribution process. The classical methods of distributing cryptographic keys (i.e., via human couriers or electronic means) are inherently insecure. Since they are subject to compromise — to achieve certainly verifiable cryptography a system is needed that can guarantee the inviolability of the key distribution process. Quantum key distribution, or QKD, is the science of distributing cryptographic keys using the properties of quantum physics. Combined with the perfectly secret one time pad cipher a QKD cryptosystem can achieve certainly verifiable cryptography. This paper introduces the reader to the domain of QKD and the aspects of quantum physics that relate to it.

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