Six-state protocol

The six-state protocol first appeared in the article "Optimal Eavesdropping in Quantum Cryptography with Six States"[1] by Dagmar Bruss in 1998, and was further studied in "Incoherent and coherent eavesdropping in the six-state protocol of quantum cryptography"[2] by Pasquinucci and Nicolas Gisin in 1999.

High dimensional systems have been proven to provide a higher level of security.

Six-state protocol can be implemented without a quantum computer using only optical technologies.

[7]Alice randomly generates a qubit string, encodes them using randomly chosen one of three bases, and sends string of qubits to Bob through the secured quantum channel.

Using classical insecure, but authenticated, channel Alice and Bob communicate and discard measurements where Bob used the different basis for measure the state of the qubit than basis that Alice used for encoding.