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Journal of Physics Conference Series

Indefinite Quantum Key Agreement code involving a third party extendable to several participants

G. Juárez Rangel, Carlos Latorre-Valdivia, Francisco Delgado

Published Jun 1, 2025• 1 citation
Publisher

Abstract

Abstract Quantum Key Agreement (QKA) is a current research topic within quantum cryptography where two or more parties collaboratively generate a shared secret key, commonly without individual full control of it. This work proposes a QKA method involving a third party other than the transmitter and receiver. Based on an initial BB84 procedure as in the EBB84 protocol, participants create an indefinite key, which becomes strong against multiple intercept-resend attacks. The process does not need decoy photons as in many other QKA protocols. Security improvements against eavesdropping are observed as compared with the BB84 protocol. The proposal could be designed to reach eavesdropping failure probabilities of 5 16 on average and fidelities lower than 1 4 for the modified state during the attack. The simplicity of the proposed protocol allows its implementation for more than two participants with current technology for the protection of information. Overall, it gives an understanding of the process used to share secured information between several parties without a previous agreement.

DOI
10.1088/1742-6596/3027/1/012033

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Abstract Quantum Key Agreement (QKA) is a current research topic within quantum cryptography where two or more parties collaboratively generate a shared secret key, commonly without individual full control of it. This work proposes a QKA method involving a third party other than the transmitter and receiver. Based on an initial BB84 procedure as in the EBB84 protocol, participants create an indefinite key, which becomes strong against multiple intercept-resend attacks. The process does not need decoy photons as in many other QKA protocols. Security improvements against eavesdropping are observed as compared with the BB84 protocol. The proposal could be designed to reach eavesdropping failure probabilities of 5 16 on average and fidelities lower than 1 4 for the modified state during the attack. The simplicity of the proposed protocol allows its implementation for more than two participants with current technology for the protection of information. Overall, it gives an understanding of the process used to share secured information between several parties without a previous agreement.
In Quantum Key Agreement (QKA) protocol, two or more participants agree to share a quantum key. Participants must meet the following conditions: (1) Can be toggled per participant. Important decisions are not made by individual participants. (2) Only participants can access the key, which is not viewable by non-participants while unauthorized acquisition of keys is impossible. Key agreement protocols are used to generate cryptographic keys in many modern applications such as IoT applications, healthcare systems, vehicle communications, intelligent networks, satellite communications, and cloud applications. To resist quantum attacks, several security protocols based on quantum physics principles have been proposed to address various security issues. The main goal of this research is to provide fundamental background information along with a detailed analysis of the theoretical aspects of QKA. The emphasis is particularly on various kinds of multiparty quantum key agreement protocols considering their design and effectiveness, with a specific spotlight on the utilization of the BB84 protocol.
Abstract The semi-quantum key agreement (SQKA) protocol enables classical participants to complete key agreement with limited quantum capabilities. The previous semi-quantum key agreement protocols required the classical party to have the ability to measure qubits, and share a key before the protocol began. This paper proposes a SQKA protocol that allows semi-quantum participants to use single photons for key negotiation with the help of a semi-honest third party (TP). Unlike previous approaches, this protocol further reduces the quantum capability requirements for participants and eliminates the need for prior key sharing. Furthermore, through security analysis and multi-party expansion, the protocol can resist external attacks such as the intercept-resend attack, measure-resend attack, entangle-measure attack. Additionally, it can be applied to scenarios involving different numbers of participants.
Quantum cryptography is a well-stated field within quantum applications where quantum information is used to set secure communications, authentication, and secret keys. Now used in quantum devices with those purposes, particularly Quantum Key Distribution (QKD), which proposes a secret key between two parties free of effective eavesdropping, at least at a higher level than classical cryptography. The best-known quantum protocol to securely share a secret key is the BB84 one. Other protocols have been proposed as adaptations of it. Most of them are based on the quantum indeterminacy for non-orthogonal quantum states. Their security is commonly based on the large length of the key. In the current work, a BB84-like procedure for QKD based on double quantum teleportation allows the sharing of the key statement using several parties. Thus, the quantum bits of information are assembled among three parties via entanglement, instead of travelling through a unique quantum channel as in the traditional protocol. Asymmetry in the double teleportation plus post-measurement retains the secrecy in the process. Despite requiring more complex control and resources, the procedure dramatically reduces the probability of success for an eavesdropper under individual attacks, because of the ignorance of the processing times in the procedure. Quantum Bit Error Rate remains in the acceptable threshold and it becomes configurable. The article depicts the double quantum teleportation procedure, the associated control to introduce the QKD scheme, the analysis of individual attacks performed by an eavesdropper, and a brief comparison with other protocols.
Quantum key distribution (QKD) and quantum key agreement (QKA) are two main branches of key establishment in quantum cryptography. However, the research of QKA falls far behind that of QKD, especially in practicability. The main reason is that QKA needs to resist not only the outside eavesdropping but also the participant cheating. Resisting dishonest participant is more difficult than resisting outside eavesdropping, especially when the apparatuses are imperfect. Actually, existing QKA protocols cannot tolerate the channel loss and have to rely on stable quantum storage. To solve this problem, we give a new quantum multi-party key agreement protocol based on the error-correcting code. Our protocol is loss tolerant, and the participants can measure the received qubits immediately in one of two conjugate bases, without storage, so our protocol can eliminate the requirement of quantum storage. Besides, our protocol is more fair because it can partially discriminate dishonest participants' cheating from outside eavesdropping (previously, these two attacks are generally checked simultaneously via decoy states but cannot be discriminated), as a result, dishonest participants generally will not cheat at the cost of losing good reputation.
Quantum key agreement (QKA) can generate a shared secret key which is equally negotiated by all the participants in the protocol. In most of the QKA protocols, all the participants require quantum capabilities. But the quantum devices are too expensive for participants. This paper proposes a mutual semi-quantum key agreement protocol which allows two parties (Alice and Bob) to negotiate a shared secret key equally. In the protocol, Alice can perform any quantum operation, but Bob is a classical participant which can only perform reflection, measurement and reorder operation. Even though Bob has fewer quantum resources, Alice and Bob have an equal contribution to the shared final key, no one can determine the shared key alone. In addition, we demonstrate the security of the proposed protocol. The analysis results show that the proposed protocol not only resists against some common attacks but also assures the fairness property. It is significant for communication participant without enough quantum devices to achieve quantum communication. The proposed protocol can be implemented with present quantum technologies.