Novel Multi-Party Quantum Key Agreement Protocol with G-Like States and Bell States

A significant aspect of quantum cryptography is quantum key agreement (QKA), which ensures the security of key agreement protocols by quantum information theory. The fairness of an absolute security multi-party quantum key agreement (MQKA) protocol demands that all participants can affect the protocol result equally so as to establish a shared key and that nobody can determine the shared key by himself/herself. We found that it is difficult for the existing multi-party quantum key agreement protocol to withstand the collusion attacks. Put differently, it is possible for several cooperated and untruthful participants to determine the final key without being detected. To address this issue, based on the entanglement swapping between G-like state and Bell states, a new multi-party quantum key agreement protocol is put forward. The proposed protocol makes full use of EPR pairs as quantum resources, and adopts Bell measurement and unitary operation to share a secret key. Besides, the proposed protocol is fair, secure and efficient without involving a third party quantum center. It demonstrates that the protocol is capable of protecting users’ privacy and meeting the requirement of fairness. Moreover, it is feasible to carry out the protocol with existing technologies.     

Quantum Key Agreement Against Collective Decoherence

A robust and efficient quantum key agreement (QKA) protocol is presented with decoherence-free (DF) states and single-particle measurements. Compared with all the previous QKA protocols, which are designed in ideal condition, this protocol can not only guarantee both the security and fairness of the shared key but also be immune to collective decoherence. In addition, our protocol has a high intrinsic efficiency due to the utilization of the delayed measurement technique. Finally, we show that the proposed protocol is secure against the attacks from both outside eavesdroppers and inside dishonest participants.     

基于Bell态的三方量子密钥协商

提出了基于两粒子纠缠态的一个三方量子密钥协商协议. 方案中的三个参与者是完全对等的, 且对建立的共享密钥具有相同的贡献. 除此之外, 三方中的任何一方或两方都不能事先单独决定共享密钥. 安全分析表明本协议既能抵抗外部窃听者的攻击, 又能抵抗内部参与者攻击. 关键词： 量子密码学 量子密钥协商 Bell态     

Improvement of “Novel Multiparty Quantum Key Agreement Protocol with GHZ States”

Quantum key agreement (QKA) protocol is a method for negotiating a fair and secure key among mutually untrusted participants. Recently, Xu et al. (Quantum Inf. Process. 13:2587–2594, 2014) proposed a multi-party QKA protocol based on Greenberger-Horne-Zeilinger (GHZ) states. However, this study points out that Xu et al.’s protocol cannot provide the fairness property. That is, the last involved participant in the protocol can manipulate the final shared secret key without being detected by the other participants. Moreover, according to Yu et al.’s research (2015), Xu et al.’s protocol cannot avoid the public discussion attack too. To avoid these weaknesses, an improved QKA protocol is proposed.     

Improvement on “Quantum Key Agreement Protocol with Maximally Entangled States”

Recently, Hsueh and Chen [in Proceedings of the 14th Information Security Conference, National Taiwan University of Science and Technology, Taipei, pp. 236–242, 2004] proposed a quantum key agreement (QKA) protocol with maximally entangled states. Their protocol allows two users to negotiate a secret key in such a way that no one can predetermine the shared key alone. This study points out two security flaws in their protocol: (1) a legitimate but malicious user can fully control the shared key alone; (2) an eavesdropper can obtain the shared key without being detected. A possible solution is presented to avoid these attacks and also Tsai et al.’s CNOT attack [in Proceedings of the 20th Cryptology and Information Security Conference, National Chiao Tung University, Hsinchu, pp. 210–213, 2010] on Hsueh and Chen protocol to obtain the shared key without being detected.     

Improved multiparty quantum key agreement in travelling mode

The need to simultaneously balance security and fairness in quantum key agreement (QKA) makes it challenging to design a flawless QKA protocol, especially a multiparty quantum key agreement (MQKA) protocol. When designing an MQKA protocol, two modes can be used to transmit the quantum information carriers: travelling mode and distributed mode. MQKA protocols usually have a higher qubit efficiency in travelling mode than in distributed mode. Thus, several travelling mode MQKA protocols have been proposed. However, almost all of these are vulnerable to collusion attacks from internal betrayers. This paper proposes an improved MQKA protocol that operates in travelling mode with Einstein-Podolsky-Rosen pairs. More importantly, we present a new travelling mode MQKA protocol that uses single photons, which is more feasible than previous methods under current technologies.     

New Probabilistic Quantum Key Distribution Protocol

On the basis of entanglement swapping of Bell states, Hwang et al. proposed a probabilistic quantum key distribution (PQKD) protocol Quantum Inf. Comput. 11(7-8), 615–637 (2011). Recently, Lin et al. Quantum Inf. Comput. 14(9-10), 757–762 (2014) proposed a unitary operation attack on Hwang et al.’s PQKD. However, unlike the unitary operation attack, this work points out that a malicious participant in Hwang et al.’s PQKD protocol can manipulate the secret key. As a result, the security requirements of a PQKD protocol, i.e., fairness, cannot be satisfied in their protocol. Moreover, the same attack can also crack the fairness requirement of the existing quantum key agreement (QKA) protocols. To overcome both problems, this paper proposes a new PQKD protocol based on the order rearrangement of the transmitted photons. Furthermore, the rearrangement method can also solve the key manipulation attack in QKA protocols.     

Multiparty Quantum Key Agreement Based on Three-Photon Entanglement with Unidirectional Qubit Transmission

A multiparty quantum key agreement protocol based on three-photon entangled states is proposed. In this scheme, the quantum channel between all parties is that of a closed loop, in which the qubit transmission is one-way. Each party can obtain the sum of the other parties’ secret key values through the coding rules instead of extracting their private keys. The shared secret key cannot be determined by any subset of all the participants except the universal set and each party makes an equal contribution to the final key. Moreover, the security analysis shows our protocol can resist both outside attacks and inside attacks.

     

A Multi-party Quantum Key Agreement Protocol Based on Shamir’s Secret Sharing

Quantum networks can extend the advantages of quantum key distribution protocols to more than two remote participants. Based on Shamir threshold secret sharing scheme, a new quantum key agreement protocol on a quantum network with any number of participants is proposed. First, each participant and distributor negotiate a sub-secret key using a kind of quantum key distribution protocol, and then each of these participants, as distributor, shares these sub-secret keys with other participants using Shamir threshold secret sharing scheme. Furthermore, each participant combines all these shared sub-secret keys and his own sub-secret key in sequence to form secret key, and sends the hash function values of this secret key to the master distributor to authenticate, finally they obtain the security key. Our scheme is practical and secure, and it can also prevent fraudulent from participants.

     

Three-Party Quantum Key Agreement with Two-Photon Entanglement

A three-party quantum key agreement protocol with two-qubit entangled states is proposed. In this paper, the three parties are entirely peer entities and each party has a equal contribution to the establishment of the shared secret key. Moreover, any subset of the three participants except the universal set can not determine the shared key alone. Finally, the security analysis shows that the present protocol can resist against both the outsider attack and the insider attack.     

Multi-Party Quantum Key Agreement by an Entangled Six-Qubit State

Since the first quantum key agreement protocol based on Bell state was presented by Zhou et al., much attention has focused on it, which is based on entangled states and product states. In this paper, we propose a multi-party quantum key agreement protocol, in which the genuinely maximally entangled six-qubit states are used. The presented protocol allows participants to share a secret key and preserves the following advantages. First, the outcome of the protocol is influenced by all parties; Second, the presented protocol is fairness, i.e., no one can determine the shared key alone; Third, outside eavesdroppers cannot gain the generated key without introducing any error. The security analysis shows that our protocol can resist both outside attacks and inside attacks.     

Multi-party Quantum Key Agreement without Entanglement

A new efficient quantum key agreement protocol without entanglement is proposed. In this protocol, each user encodes his secret key into the traveling particles by performing one of four rotation operations that one cannot perfectly distinguish. In the end, all users can simultaneously obtain the final shared key. The security of the presented protocol against some common attacks is discussed. It is shown that this protocol can effectively protect the privacy of each user and satisfy the requirement of fairness in theory. Moreover, the quantum carriers and the encoding operations used in the protocol can be achieved in realistic physical devices. Therefore, the presented protocol is feasible with current technology.     

Three-Party Quantum Key Agreement Protocol Based on Continuous Variable Single-Mode Squeezed States

The difficulty of quantum key agreement is to realize its security and fairness at the same time.This paper presents a new three-party quantum key agreement protocol based on continuous variable single-mode squeezed state.The three parties participating in the agreement are peer entities,making same contributions to the final key.Any one or two participants of the agreement cannot determine the shared key separately.The security analysis shows that the proposed protocol can resist both external and internal attacks.     

Multi-Party Quantum Key Agreement Protocol with Bell States and Single Particles

International Journal of Theoretical Physics - Liu et al. [Quantum Inf. Process. 12, 1797–1805 (2013)] proposed a multi-party quantum key agreement (QKA) protocol based on single particles....     

Three-step semiquantum secure direct communication protocol

Quantum secure direct communication is the direct communication of secret messages without need for establishing a shared secret key first. In the existing schemes, quantum secure direct communication is possible only when both parties are quantum. In this paper, we construct a three-step semiquantum secure direct communication (SQSDC) protocol based on single photon sources in which the sender Alice is classical. In a semiquantum protocol, a person is termed classical if he (she) can measure, prepare and send quantum states only with the fixed orthogonal quantum basis {|0〉, |1〉}. The security of the proposed SQSDC protocol is guaranteed by the complete robustness of semiquantum key distribution protocols and the unconditional security of classical one-time pad encryption. Therefore, the proposed SQSDC protocol is also completely robust. Complete robustness indicates that nonzero information acquired by an eavesdropper Eve on the secret message implies the nonzero probability that the legitimate participants can find errors on the bits tested by this protocol. In the proposed protocol, we suggest a method to check Eves disturbing in the doves returning phase such that Alice does not need to announce publicly any position or their coded bits value after the photons transmission is completed. Moreover, the proposed SQSDC protocol can be implemented with the existing techniques. Compared with many quantum secure direct communication protocols, the proposed SQSDC protocol has two merits: firstly the sender only needs classical capabilities; secondly to check Eves disturbing after the transmission of quantum states, no additional classical information is needed.     

A （2, 3） quantum threshold scheme based on Greenberger-Horne-Zeilinger state

In this paper, by using properties of quantum controlled-not manipulation and entanglement states, we have designed a novel (2, 3) quantum threshold scheme based on the Greenberger- Horne -Zeilinger (GHZ) state. The proposed scheme involves two phases, i.e. a secret sharing phase and a secret phase. Detailed proofs show that the proposed scheme is of unconditional security. Since the secret is shared among three participants, the proposed scheme may be applied to quantum key distribution and secret sharing.     

Multiparty Quantum Key Agreement with Four-Qubit Symmetric W State

Based on four-qubit symmetric W state, the delayed measurement, decoy photos method, block transmission technique and the dense coding method, a multi-party quantum key agreement protocol is proposed. By utilizing the delayed measurement and decoy photos method, the fairness and security of the protocol are ensured. That is, the final generation key can be got fairly by m participants and the outside eavesdropper (includes Trojan-horse attacks, Measure-resend attack, Intercept-resend attack and Entangle-measure attack) and the dishonest participants attacks can be resisted in this protocol. By utilizing block transmission technique and the dense coding method, the efficiency of the protocol is improved. The efficiency analysis shows that the proposed protocol is more efficient than other multi-party QKA protocols.     

Three-Party Semi-Quantum Key Agreement Protocol

International Journal of Theoretical Physics - A semi-quantum key agreement protocol is proposed to allow one quantum participant and two classical ones to negotiate the final shared secret key...     

Three Attacks on the Mediated Semi-Quantum Key Distribution without Invoking Quantum Measurement

Semi-quantum key distribution is a very interesting new branch of quantum key distribution. It can be implemented when one or more participants are restricted to operate quantum states only on the quantum computational basis. Very recently, a mediated semi-quantum key distribution protocol without invoking two participants' quantum measurement has been proposed. The protocol allows two “classical” participants without sophisticated quantum capability to establish a shared secret key under an untrusted third party. It is claimed that the protocol is secure against several well-known attacks. However, in this paper, it is first pointed out that there exist three attacks “Measurement Attack, Modification Attack, and Collective Attack” on the mediated semi-quantum key distribution protocol without invoking quantum measurement. By proposed attacks, a malicious third party can obtain the secret key without being noticed by legitimated participants.     

Large-capability quantum key distribution with entangled qutrits

A secure quantum key distribution protocol is proposed to distribute the three-dimensional secret message in a two-way quantum channel based on the entanglement of two-qutrit quantum system. The present protocol has an advantage over transmitting directly the secret message with large capacity since the distributed message has been imposed on nonorthogonal two-qutrit-entangled states by the sender using the superdense coding via local unitary operations. The security is ensured by the entanglement of the two-qutrit quantum system and the secure transmission of the traveling-particle sequence in the lossless and noiseless channel.