Quantum cryptography is the application of quantum mechanics principles to encryption to better secure connections between two parties. It gained traction in the 1980s when Charles Bennett and Gilles Brassard introduced their quantum key distribution protocol, called BB84. Quantum key distribution uses subatomic light particles – photons – as a means of choosing a secret encryption key. Before generating the key, the two parties must interact and authenticate their identities. Then photons are sent across a cable and are randomly divided by a beam splitter. The remaining photons determine the key, which is now known only to the communicating parties.
Quantum key distribution should be used with other encryption practices for best possible security. It has failed before, but that was due to faulty implementation rather than the principles of quantum mechanics, which are reliable and consistent.
Mistrustful quantum cryptography uses different methods of creating an encrypted connection, such as coin flipping and oblivious transfer. The two parties don’t trust each other, which increases the likelihood of cheating, and it’s typically impossible to create unconditional security. Methods of mistrustful quantum cryptography should be used with other encryption methods.
The benefit of quantum cryptography is its security. Because the connection between the two parties is established using photons, any attempted breach will clearly disturb the photons. Those parties will notice anyone attempting to eavesdrop or interrupt the communication. A cryptographic connection established by physics is more secure than other encryption protocols; its security can be proven through physics principles.