Quantum Secure Communication Scheme with W State

We present a quantum secure communication scheme using three-qubit W state. It is unnecessary for the present scheme to use alternative measurement or Bell basis measurement. Compared with the quantum secure direct communication scheme proposed by Cao et at. [H.J. Cao and H.S. Song, Chin. Phys. Lett. 23 （2006） 290], in our scheme, the detection probability for an eavesdropper＇s attack increases from 8.3% to 25%. We also show that our scheme is secure for a noise quantum channel.

Quantum Secure Communication Using a Class of Three-Particle W State

A theoretical scheme of quantum secure communication using a class of three-particle W states is proposed. In the scheme,two communicators may communicate after they test the security of the quantum channel.The receiver can obtain the secret message determinately if the quantum channel is safe.The present scheme can be realized without using teleportation.

Efficient Quantum Secure Communication Protocol by Rearranging Particle Orders

We propose a quantum secure communication protocol by using three-particle GHZ states. In this protocol, we utilize the ideas of the rearranging orders and the sequence transmission. The sender of messages, Alice, first disturbs the particle orders in an initial sequence, and then sends the sequence of the disturbed orders to the receiver of messages, Bob. Under Alice＇s introduction, Bob rearranges the sequence back to the initial sequence. By making a GHZ state measurement on each of the three particles in turn, Bob can attain Alice＇s secret messages. In addition, we still calculate the efficiency of our three-particle GHZ protocol and generalize it to the case using multi-particle GHZ state.

Efficient quantum secure communication with a publicly known key

This paper presents a simple way for an eavesdropper to eavesdrop freely the secret message in the experimental realization of quantum communication protocol proposed by Beige et al （2002 Acta Phys. Pol. A 101 357）. Moreover, it introduces an efficient quantum secure communication protocol based on a publicly known key with decoy photons and two biased bases by modifying the original protocol. The total efficiency of this new protocol is double that of the original one. With a low noise quantum channel, this protocol can be used for transmitting a secret message. At present, this protocol is good for generating a private key efficiently,

A Protocol for Bidirectional Quantum Secure Communication Based on Genuine Four-Particle Entangled States

By swapping the entanglement of genuine four-particle entangled states,we propose a bidirectional quantumsecure communication protocol.The biggest merit of this protocol is that the information leakage does not exist.Inaddition,the ideas of the 'two-step' transmission and the block transmission are employed in this protocol.In order toanalyze the security of the second sequence transmission,decoy states are used.

Quantum Secure Communication by Using GHZ State in High-Dimensional Hilbert Space

We propose a quantum superdense coding secure communication scheme by using GHZ state.This scheme combines the ideas of quantum superdense coding and sequence transmission.Its distinct advantage is high source capacity.In addition,in checking eavesdropping,we need not to destroy quantum entanglement.

High-Capacity Quantum Secure Communication with Authentication Using Einstein-Podolsky-Rosen Pairs

A new protocol for quantum secure communication with authentication is proposed. The proposed protocol has a higher capacity as each EPR pair can carry four classical bits by the XOR operation and an auxiliary photon. Tile security and efficiency are analyzed in detail and the major advantage of this protocol is that it is more efficient without losing security.

Three-Party Simultaneous Quantum Secure Communication Based on Closed Transmission Loops

A kind of novel three-party quantum secure direct communication protocol is proposed with the correlation of two-particle entangled state. In this scheme the qubit transmission forms a closed loop and every one of the three participants is both a receiver and a sender of particle sequences in the bidirectional quantum channels. Each party implements the corresponding unitary operations according to its secret bit value over the quantum channels and then extracts the other two parties’ unitary operations by performing Bell measurements on the encoded particles. Thus they can obtain the secret information simultaneously. Finally, the security analysis shows that the present three-party scheme is a secure protocol.

Quantum Cryptography for Internet of Things Security

Internet of things (IoT) is a developing technology with a lot of scope in the future. It can ease various different tasks for us. On one hand, IoT is useful for us, on the other hand, it has many serious security threats, like data breaches, side-channel attacks, and virus and data authentication. Classical cryptographic algorithms, like the Rivest-Shamir-Adleman (RSA) algorithm, work well under the classical computers. But the technology is slowly shifting towards quantum computing, which has immense processing power and is more than enough to break the current cryptographic algorithms easily. So it is required that we have to design quantum cryptographic algorithms to prevent our systems from security breaches even before quantum computers come in the market for commercial uses. IoT will also be one of the disciplines, which needs to be secured to prevent any malicious activities. In this paper, we review the common security threats in IoT and the presently available solutions with their drawbacks. Then quantum cryptography is introduced with some of its variations. And finally, the analysis has been carried out in terms of the pros and cons of implementing quantum cryptography for IoT security.

Fault tolerant quantum secure direct communication with quantum encryption against collective noise

We present two novel quantum secure direct communication（QSDC） protocols over different collective-noise channels.Different from the previous QSDC schemes over collective-noise channels,which are all source-encrypting protocols,our two protocols are based on channel-encryption.In both schemes,two authorized users first share a sequence of EPR pairs as their reusable quantum key.Then they use their quantum key to encrypt and decrypt the secret message carried by the decoherence-free states over the collective-noise channel.In theory,the intrinsic efficiencies of both protocols are high since there is no need to consume any entangled states including both the quantum key and the information carriers except the ones used for eavesdropping checks.For checking eavesdropping,the two parties only need to perform two-particle measurements on the decoy states during each round.Finally,we make a security analysis of our two protocols and demonstrate that they are secure.

Improvement on Quantum Secure Direct Communication with W State in Noisy Channel

An improvement （Y-protocol） [Commun. Theor. Phys. 49 （2008） 103] on the quantum secure direct communication with W state （C-protocol） [Chin. Phys. Lett. 23 （2006） 290] is proposed by Yuan et al. The quantum bit error rate induced by eavesdropper is 4.17% in C-protocol and 6.25% in Y-protocoL In this paper, another improvement on C-protocol is given. The quantum bit error rate of the eavesdropping will increase to 8.75%, which is 1.1 times larger than that in C-protocol and 0.4 times larger than that in Y-protocol.

Analysis and Improvement of an Efficient Controlled Quantum Secure Direct Communication and Authentication Protocol

The controlled quantum secure direct communication(CQSDC)with authentication protocol based on four particle cluster states via quantum one-time pad and local unitary operations is cryptanalyzed.It is found that there are some serious security issues in this protocol.An eavesdropper(Eve)can eavesdrop on some information of the identity strings of the receiver and the controller without being detected by the selective-CNOT-operation(SCNO)attack.By the same attack,Eve can also steal some information of the secret message that the sender transmits.In addition,the receiver can take the same kind of attack to eavesdrop on some information of the secret message out of the control of the controller.This means that the requirements of CQSDC are not satisfied.At last,we improve the original CQSDC protocol to a secure one.

Quantum Secure Direct Communication Using Entangled Photon Pairs and Local Measurement

We present a scheme for quantum secure direct communication,in which the message is encoded bylocal unitary operations,transmitted through entangled photons,and deduced from both the sender and receiver's localmeasurement results.In such a scheme,only one pair of entangled photons is consumed,and there is no need to transmitthe sender's qubit carrying the secret message in a public channel,in order to transmit two-bit classical information.

Two-step quantum secure direct communication scheme with frequency coding

Quantum secure direct communication （QSDC） is an important branch of quantum cryptography. It can transmit secret information directly without establishing a key first, unlike quantum key distribution which requires this precursory event. Here we propose a QSDC scheme by applying the frequency coding technique to the two-step QSDC protocol, which enables the two-step QSDC protocol to work in a noisy environment. We have numerically simulated the performance of the protocol in a noisy channel, and the results show that the scheme is indeed robust against channel noise and loss. We also give an estimate of the channel noise upper bound.

Quantum Secure Direct Intercommunication with Superdense Coding and Entanglement Swapping

A quantum secure direct intercommunication scheme is proposed to exchange directly the communicators＇ secret messages by making ase of swapping entanglement of Bell states. It has great capacity to distribute the secret messages since these messages have been imposed on high-dimensional Bell states via the local unitary operations with superdense coding. The security is ensured by the secure transmission of the travel sequences and the application of entanglement swapping.

Improving the security of secure deterministic communication scheme based on quantum remote state preparation

The security of the quantum secure deterministic communication scheme [Chin. Phys.16 （2007） 2549] is reexamined. A security loophole is pointed out. Taking advantage of this loophole, an eavesdropper can steal all the secret messages without being detected by an intercept-and-resend attack strategy. Furthermore, a possible improvement on this protocol is presented. It makes the modified protocol secure against this kind of attack.

Robust Quantum Secure Direct Communication over Collective Rotating Channel

A quantum secure direct communication protocol over a collective rotating channel is proposed. The protocol encodes logical bits in noiseless subspaces, and so it can function over a quantum channel subjected to an arbitrary degree of collective rotating noise. Although entangled states are used, both the sender and receiver are only required to perform single-particle product measurement or Pauli operations. The protocol is feasible with present-day technique.

Secure deterministic communication scheme based on quantum remote state preparation

Based on the techniques of the quantum remote state preparation via a deterministic way, this paper proposes a quantum communication scheme to distribute the secret messages in two phases, i.e., the carrier state checking phase and the message state transmitting phase. In the first phase, the secret messages are encoded by the sender using a stabilizer quantum code and then transmitted to the receiver by implementing three CNOT gates. In the second phase, the communicators check the perfectness of the entanglement of the transmitted states. The messages can be distributed to the receiver even if some of the transmitted qubits are destroyed.

Quantum secure direct communication with quantum encryption based on pure entangled states

This paper presents a scheme for quantum secure direct communication with quantum encryption. The two authorized users use repeatedly a sequence of the pure entangled pairs （quantum key） shared for encrypting and decrypting the secret message carried by the travelling photons directly. For checking eavesdropping, the two parties perform the single-photon measurements on some decoy particles before each round. This scheme has the advantage that the pure entangled quantum signal source is feasible at present and any eavesdropper cannot steal the message.

A two-step quantum secure direct communication protocol with hyperentanglement

We propose a two-step quantum secure direct communication （QSDC） protocol with hyperentanglement in both the spatial-mode and the polarization degrees of freedom of photon pairs which can in principle be produced with a beta barium borate crystal. The secret message can be encoded on the photon pairs with unitary operations in these two degrees of freedom independently. This QSDC protocol has a higher capacity than the original two-step QSDC protocol as each photon pair can carry 4 bits of information. Compared with the QSDC protocol based on hyperdense coding, this QSDC protocol has the immunity to Trojan horse attack strategies with the process for determining the number of the photons in each quantum signal as it is a one-way quantum communication protocol.