Two conditions must be satisfied in a secure quantum key agreement (QKA) protocol: (1) outside eavesdroppers cannot gain the generated key without introducing any error; (2) the generated key cannot be determined by any non-trivial subset of the participants. That is, a secure QKA protocol can not only prevent the outside attackers from stealing the key, but also resist the attack from inside participants, i.e. some dishonest participants determine the key alone by illegal means. How to resist participant attack is an aporia in the design of QKA protocols, especially the multi-party ones. In this paper we present the first secure multiparty QKA protocol against both outside and participant attacks. Further more, we have proved its security in detail.

Multiparty quantum key agreement with single particles

As an important branch of quantum cryptography, quantum private comparison (QPC) has recently received a lot of attention. In this paper we study the security of previous QPC protocols with a semi-honest third party (TP) from the viewpoint of secure multi-party computation and show that the assumption of a semi-honest TP is unreasonable. Without the unreasonable assumption of a semi-honest TP, one can easily find that the QPC protocol (Tseng et al. in Quantum Inf Process, 2011, doi: 10.1007/s11128-011-0251-0 ) has an obvious security flaw. Some suggestions about the design of QPC protocols are also given.

Comment on quantum private comparison protocols with a semi-honest third party

In many circumstances, a shared key is needed to realize secure communication. Based on quantum mechanics principles, quantum key agreement (QKA) is a good method to establish a shared key by every party's fair participation. In this paper, we propose a novel three-party QKA protocol, which is designed by using Greenberger---Horne---Zeilinger (GHZ) states. To realize the protocol, the distributor of the GHZ states needs only one quantum communication with the other two parties, respectively, and everyone performs single-particle measurements simply. Then, we extend the three-party QKA protocol to arbitrary multiparty situation. At last, we discuss the security and fairness of the multiparty protocol. It shows that the new scheme is secure and fair to every participant.

Novel multiparty quantum key agreement protocol with GHZ states

Two efficient quantum private comparison (QPC) protocols are proposed, employing single photons and collective detection. In the proposed protocols, two distrustful parties (Alice and Bob) compare the equivalence of information with the help of a semi-honest third party (TP). Utilizing collective detection, the cost of practical realization is reduced greatly. In the first protocol, TP gains the result of the comparison. While in the second protocol, TP cannot get the comparison result. In both of our protocols, Alice and Bob only need be equipped with unitary operation machines, such as phase plates. So Alice and Bob need not to have the expensive quantum devices, such as qubit generating machine, quantum memory machine and quantum measuring machine. Security of the protocols is ensured by theorems on quantum operation discrimination.

Efficient quantum private comparison employing single photons and collective detection

In this paper, a quantum private comparison protocol is proposed based on bell entangled states. In our protocol, two parties can compare the equality of their information with the help of a semi-honest third party. The correctness and security of our protocol are discussed. One party cannot learn the other's private information and the third party also cannot learn any information about the private information.

Quantum Private Comparison Protocol Based on Bell Entangled States

Based on EPR pairs, this paper proposes a different quantum private comparison (QPC) protocol enabling two parties to compare the equality of their information without revealing the information content. Due to the use of quantum entanglement of Bell state as well as one-way quantum transmission, the new protocol provides easier implementation as well as better qubit efficiency (near 50%) than the other QPCs. It is secure against Trojan horse attack and other well-known attacks.

New quantum private comparison protocol using EPR pairs

Intercept–resend attacks on Chen et al.'s quantum private comparison protocol and the improvements

Quantum secret sharing (QSS) and quantum search algorithm (QSA) are considered as two important but different research topics in quantum information science. This paper recognizes an important feature in the well-known Grover’s QSA and then applies it to propose a QSS protocol. In contrast to the existing QSA-based QSS protocols, the newly proposed protocol has the following two advantages: (1) no quantum memory is required by the agents, whereas the agents in the existing QSA-based QSS protocols need long-term quantum memories to store their secret shadows; (2) the agents can cooperate to recover the boss’s secret by using shadows in classical bits, whereas, the others have to combine their shadows in photons and perform a unitary operation on the retained photons. The proposed QSS protocol is also shown to be secure against eavesdroppers or malicious agents.

Quantum Secret Sharing Based on Quantum Search Algorithm

In this study, we propose a controlled deterministic secure quantum communication (CDSQC) protocol based on the idea of Grover’s quantum search algorithm (QSA). The proposed protocol has the following two advantages over the existing CDSQC protocols: (1) high qubit frequency and (2) less quantum memory. Moreover, the security analysis of the proposed protocol shows that any eavesdropper will be detected with a very high probability under both ideal and noisy quantum channel conditions.

Controlled Deterministic Secure Quantum Communication Based on Quantum Search Algorithm

Recently, Xiu et al. proposed a deterministic secure quantum communication (DSQC) protocol using the entanglement swapping of four-particle genuine entangled states. Later, Qin et al. showed a double-CNOT attack on the protocol and also provided an improvement to avoid the attack. This work tries to use a batch of decoy single photons prepared randomly in one of four different states, to enhance the qubit efficiency on their DSQC protocols and avoid the double-CNOT attack at the same time.

Hsin-Yi Tseng

Papers

New quantum private comparison protocol using EPR pairs

Intercept–resend attacks on Chen et al.'s quantum private comparison protocol and the improvements

Quantum Secret Sharing Based on Quantum Search Algorithm

Controlled Deterministic Secure Quantum Communication Based on Quantum Search Algorithm

On the "Deterministic Secure Quantum Communication using Four-Particle Entangled State and Entanglement Swapping"