The three-stage quantum cryptography protocol, also known as Kak's three-stage protocol is a method of data encryption that uses random polarization rotations by both

Alice and Bob Alice and Bob are fictional characters commonly used as placeholders in discussions about cryptographic systems and protocols, and in other science and engineering literature where there are several participants in a thought experiment. The Al ...

, the two authenticated parties, that was proposed by

Subhash Kak Subhash Kak is an Indian-American computer scientist and historical revisionist. He is the Regents Professor of Computer Science Department at Oklahoma State University–Stillwater, an honorary visiting professor of engineering at Jawaharlal N ...

. In principle, this method can be used for continuous, unbreakable encryption of data if single photons are used. It is different from methods of QKD (

quantum key distribution Quantum key distribution (QKD) is a secure communication method which implements a cryptographic protocol involving components of quantum mechanics. It enables two parties to produce a shared random secret key known only to them, which can then b ...

) for it can be used for direct encryption of data, although it could also be used for exchanging keys. Three stage quantum cryptography protocol

The basic idea behind this method is that of sending secrets (or valuables) through an unreliable courier by having both Alice and Bob place their locks on the box containing the secret, which is also called double-lock cryptography. Alice locks the box with the secret in it and it is transported to Bob, who sends it back after affixing his own lock. Alice now removes her lock (after checking that it has not been tampered with) and sends it back to Bob who, similarly unlocks his lock and obtains the secret. In the braided form, only one-pass suffices but here Alice and Bob share an initial key. This protocol has been proposed as a method for secure communication that is entirely quantum unlike

in which the cryptographic transformation uses classical algorithms The basic polarization rotation scheme has been implemented in hardware by Pramode Verma in the quantum optics laboratory of the

University of Oklahoma , mottoeng = "For the benefit of the Citizen and the State" , type = Public research university , established = , academic_affiliations = , endowment = $2.7billion (2021) , pr ...

. In this method more than one photon can be used in the exchange between Alice and Bob and, therefore, it opens up the possibility of multi-photon quantum cryptography. This works so long as the number of photons siphoned off by the eavesdropper is not sufficient to determine the polarization angles. A version that can deal with the

man-in-the-middle attack In cryptography and computer security, a man-in-the-middle, monster-in-the-middle, machine-in-the-middle, monkey-in-the-middle, meddler-in-the-middle, manipulator-in-the-middle (MITM), person-in-the-middle (PITM) or adversary-in-the-middle (AiTM) ...

has also been advanced. Parakh analyzed the three-stage protocol under rotational quantum errors and proposed a modification that would correct these errors. One interesting feature of the modified protocol is that it is invariant to the value of rotational error and can therefore correct for arbitrary rotations.

References

{{Reflist Quantum cryptography

See also

References