Kak's three stage protocol

Kak's three stage protocol is a little known protocol for quantum cryptography that was suggested by Subhash Kak who has named the scheme after himself. Although it is also open to the man-in-the-middle attacks like the BB type of quantum cryptography protocols, it uses only quantum transformations which makes it quite different from other systems.

S. Kak, “A Three-Stage Quantum Cryptography Protocol,” Foundations of Physics Letters 19 (2006), 293-296.

Practical issues related to its implementation will determine whether it will ever be widely used.