We present a controlled quantum key distribution protocol with a certain entangled state to solve a special cryptographic task.Also,we provide a proof of security of this protocol by generalizing the proof of the modified Lo-Chau Einstein-Podolsky-Rosen scheme.
A quantum key distribution protocol with traditional Bob has been proposed recently by Boyer et al. using single-particle state.In this paper, a semi-quantum key distribution protocol is described, in which Einstein-Podolsky-Rosen (EPR) pairs of particles are utilized to generate a secret key in remote places.This extends the quantum key distribution protocol with traditional Bob where the single-qubit channel is replaced by the entangled EPR-pair channel.And quantum Alice is able to do any quantum operations, preparing quantum states and performing quantum measurement, but traditional Bob is not able to prepare and measure a particle in the computational basis, reflect the particles.Furthermore, entanglement states are used in our protocol.The analysis shows that our protocol is secure, which can avoid the beam splitter attack automatically, and the proposed protocol is more efficient than Boyer's scheme.
We provide an asymmetrical quantum key distribution protocol based on the correlations of EPR pairs. It is a variant of the modified Lo–Chau protocol where the EPR pair is not in the state Φ+ but is in one of the four states {Φ±, Ψ±}. The two sides communicating with each other are not equal in the process of establishing the key. A public key system can be built on the protocol. It differs from classical public key system in that there are three keys: the public key, the secret key and the real key.
Entanglement swapping between Einstein-Podolsky-Rosen (EPR) pairs can be used to generate the same sequence of random bits in two remote places. A quantum key distribution protocol based on this idea is described. The scheme exhibits the following features. (a) It does not require that Alice and Bob choose between alternative measurements, therefore improving the rate of generated bits by transmitted qubit. (b) It allows Alice and Bob to generate a key of arbitrary length using a single quantum system (three EPR pairs), instead of a long sequence of them. (c) Detecting Eve requires the comparison of fewer bits. (d) Entanglement is an essential ingredient. The scheme assumes reliable measurements of the Bell operator.