Quantum three-pass cryptography protocol
Li Yang, Ling-An Wu, Songhao Liu · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2002
We present a new kind of quantum cryptography protocol based on Shamir's three-pass protocol of classical cryptography, which allows the transmission of qubits directly and secretly via the aid of an unjammable classical channel. In this protocol we implement the encryption and decryption transformations via rotations on the Poincare sphere of the photons polarization parameters. The key technique is that Bob's encryption rotation must be commutative with Alice s decryption rotation; this means that the axes of these two rotations must be parallel. We also present a security analysis of the protocol under a man-in-the-middle attack.