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Quantum cryptography is based on quantum mechanics to guarantee secure communication. It allows two parties to produce a shared random bit string known only to them. These random bits can be used as a key to encrypt and decrypt messages. The most important and unique property of quantum cryptography is the ability of the two communicating users to detect the presence of any third party trying to gain knowledge of the key. It is based on fundamental aspects of quantum mechanics. By using quantum entanglement or quantum super positions and transmitting information in quantum states, a communication system can be implemented which detects eavesdropping. Quantum cryptography is used to produce and distribute a key, not to transmit any message data. This key along with certain encryption algorithm, is used to encrypt (and decrypt) a message, which can then be transmitted over a standard communication channel. This paper concentrates on comparison between classical and quantum cryptography as well as survey on various quantum key distribution protocols used to generate and distribute the key among communicating parties. |
