Quantum Cryptography

In the most basic of descriptions, quantum cryptography is any set of cryptographic tasks that are done by quantum systems. The most famous of these systems is known as quantum key distribution (QKD). By using quantum mechanics, the crytograph can ensure a secure communication. Because of the randomness, it allows for the two parties to generate a bit string that they – being the ones that know it – can then use to encrypt or decrypt messages.

Because quantum cryptography is dealing with quantum, the two parties that are using the generated bit string are able to tell when there is a third party trying to "spy" on what is being delivered. Because a fundamental rule of quantum mechanics states that the process of trying to measure a quantum system generally disturbs the system, any attempt at an eavesdrop requires the measurement of the key and therefore, creates a detectable anomaly.

To further ensure security, what the quantum cryptography does is ensure that the eavesdropping level is below a certain threshold. If it is, a key is generated that, because there is no one eavesdropping, is guaranteed to be a secure one. However, if the level of eavesdropping is above the threshold and it is deemed that there is someone trying to measure, communication is aborted and no key is generated.

Quantum cryptography's main difference from traditional cryptography that relies on computational difficulty with mathematical equations is the fact that quantum cryptography can detect third parties. With the traditional public key cryptograhy, there is no detection or awareness of any third party. This awareness is what makes quantum cryptography such a beneficial tool to use.

A successful implementation of quantum cryptography would be to use it to generate a key. Then, attach that key as an encryption onto a packet of data. Once it has been attached and is entirely encrypted, the data can be transmitted over a traditional communication line. Quantum cryptography only creates and distributes the key, it has nothing to do with the transmission of data.

While quantum cryptography is incredibly secure, it is not used widespread because it is incredibly expensive. However, because of there being an increased amount of fiber optics already in place around the world, it is becoming increasingly less expensive to use quantum cryptography. Currently, governments that try to protect very important documents as well as instances where the normal cryptography is simply not enough employ quantum cryptography. As the research progresses and it becomes cheaper, more people will most likely use it because it does have the third party detection to it.