An improved semi-quantum secret sharing protocol with enhanced verification to counter man-in-the-middle attacks

Li et al. (Quantum Inf Process 17(10):285, 2018) proposed a limited resource semi-quantum secret sharing protocol, in which the classical participants do not equip any quantum measurement devices. However, this protocol has a security loophole. This study investigates this loophole and indicates that a malicious agent can perform the double-CNOT attack to steal partial information about the secret shadow of the other agent without being detected.

Multi-party Weighted Threshold d-Dimensional Semi-Quantum Secret Sharing Based on the Chinese Remainder Theorem

Recently, a multiparty semiquantum secret sharing scheme based on rearranging orders of qubits was proposed by Gao et al. [Mod. Phys. Lett. B 30 (2016) 1650130]. In this paper, we show that in their scheme the last agent and other agents can illegally get the sender’s secret keys without being detected. Furthermore, an improved scheme is proposed to resist such attack.

Boyer et al (2007 Phys. Rev. Lett. 99 140501) proposed a novel idea of semi-quantum key distribution, where a key can be securely distributed between Alice, who can perform any quantum operation, and Bob, who is classical. Extending the ‘semi-quantum’ idea to other tasks of quantum information processing is of interest and worth considering. In this paper, we consider the issue of semi-quantum secret sharing, where a quantum participant Alice can share a secret key with two classical participants, Bobs. After analyzing the existing protocol, we propose a new protocol of semi-quantum secret sharing. Our protocol is more realistic, since it utilizes product states instead of entangled states. We prove that any attempt of an adversary to obtain information necessarily induces some errors that the legitimate users could notice.

Based on the assumption of a perfect qubit, Boyer et al. proposed a novel semiquantum key distribution protocol [Phys. Rev. Lett. 99 (2007) 140501], in which quantum Alice shares a secret key with classical Bob. In this paper, we use Bell states to propose a multiparty semiquantum secret sharing (MSQSS) protocol, in which only the boss is quantum and all agents are classical. Classical agents are restricted to performing measurements in a computational basis and rearranging orders of qubits. Unless all classical agents collaborate, no subset of them can obtain the secret of the quantum boss. Also, we show that this proposed protocol is secure against eavesdropping.

Semi-quantum secret sharing (SQSS) protocols serve as fundamental frameworks in quantum secure multi-party computations, offering the advantage of not requiring all users to possess intricate quantum devices. However, current SQSS protocols mainly cater to bipartite scenarios, with few protocols suitable for multi-party scenarios. Moreover, the multi-party SQSS protocols face limitations such as low qubit efficiency and inability to share deterministic secret information. To address this gap, this paper proposes a multi-party SQSS protocol based on multi-particle GHZ states. In this protocol, the quantum user can distribute the predetermined secret information to multiple classical users with limited quantum capabilities, and only through mutual cooperation among all classical users can the correct secret information be reconstructed. By utilizing measure-flip and reflect operations, the transmitted multi-particle GHZ states can all contribute keys, thereby improving the utilization of transmitted particles. Then, security analysis shows that the protocol’s resilience against prevalent external and internal threats. Additionally, employing IBM Qiskit, we conduct quantum circuit simulations to validate the protocol’s accuracy and feasibility. Finally, compared to similar studies, the proposed protocol has advantages in terms of protocol scalability, qubit efficiency, and shared message types.

Seldom quantum secret sharing protocols with both the flexible (t, n) threshold and semi-quantum properties have been proposed. Recently, a novel idea of (t, n) threshold semiquantum secret sharing was proposed, which has both the (t, [Formula: see text] threshold and semi-quantum properties. Its idea can simplify the quantum secret sharing process such that many classical users with simple ability of quantum operations can realize the communication goal by cooperating with one quantum party. Furthermore, the protocol is very flexible since any t collaborators of the n classical users can reconstruct the full secret by Shamir’s threshold technology. Unfortunately, their protocol is vulnerable to the NOT-gate attack. This paper shows that an attacker can break the (t, n) threshold protocol by performing two rounds of NOT-gate attack. Then, an improved (t, n) threshold semiquantum secret sharing protocol is proposed. In the improvement scheme, each receiver can perform the eavesdropping check by measuring the Z-basis sample states. The improved protocol not only has semi-quantum properties but also can repair the security hole of the old version and has enhanced security against various quantum attacks.

Semi-quantum secret sharing facilitates the sharing of private data between quantum users and ‘classical’ users with limited quantum capabilities, thereby lowering the barrier to utilizing quantum technology. However, most current semi-quantum secret sharing protocols are confined to ideal environments and two-party scenarios. In this paper, we design two collective noise-resistant multi-party semi-quantum secret sharing protocols based on decoherence-free states to address potential noise interference during transmission. These protocols use decoherence-free states as information carriers for data interaction and exhibit strong resilience to both internal and external threats. We also conduct simulation experiments using IBM Qiskit to verify the stability and feasibility of the protocols in the noisy environments. The results of these experiments underscore the robustness of the protocols, particularly in the presence of collective noise. Compared with previous related protocols, our protocols have advantages in noise resistance and applicability to multi-party scenarios. Therefore, the proposed protocols may be more in line with the secret sharing needs of actual environments.

To ensure communication security, it is necessary to verify the identities of the communicators. Two semi-quantum identification protocols with single photons involving two parties, i.e., quantum Alice and classical Bob, are presented. In the first semi-quantum identification protocol, classical Bob can authenticate quantum Alice’s identity without the help of an authenticated classical channel. As for the second one, quantum Alice can verify the identity of classical Bob without the classical measurement ability. Semi-quantum identification is significant to ensure the security of semi-quantum key distribution, semi-quantum secret sharing and so on. The proposed two identification protocols against common attacks can be employed in several existing semi-quantum key distribution protocols based on single photons to resist the man-in-the-middle attack.

We present a semiquantum secret sharing protocol by using two-particle entangled states in which quantum Alice shares a secret key with two classical parties, Bob and Charlie. Classical Bob and Charlie are restricted to measuring, preparing a particle in the computational basis, or reflecting the particles. None of them can acquire the secret unless they collaborate. We also show the protocol is secure against eavesdropping.

Semi-quantum secret sharing in high-dimensional quantum system using product states

This study proposes a multiparty mediated quantum secret sharing (MQSS) protocol that allows n restricted quantum users to share a secret via the assistance of a dishonest third-party with full quantum capabilities. Under the premise that a restricted quantum user can only perform the Hadamard transformation and the Z-basis measurement, the proposed MQSS protocol has addressed two common challenges in the existing semi-quantum secret sharing protocols: (1) the dealer must have full quantum capability, and (2) the classical users must equip with the wavelength quantum filter and the photon number splitters to detect the Trojan horse attacks. The security analysis has also delivered proof to show that the proposed MQSS protocol can avoid the collective attack, the collusion attack, and the Trojan horse attacks. In addition, the proposed MQSS protocol is more efficient than the existing SQSS protocols due to the restricted quantum users can only equip with two quantum operations, and the qubits are transmitted within a shorter distance.

Secret sharing is a procedure for sharing a secret among a number of participants such that only the qualified subsets of participants have the ability to reconstruct the secret. Even in the presence of eavesdropping, secret sharing can be achieved when all the members are quantum. So what happens if not all the members are quantum? In this paper we propose two semi-quantum secret sharing protocols using maximally entangled GHZ-type states in which quantum Alice shares a secret with two classical parties, Bob and Charlie, in a way that both parties are sufficient to obtain the secret, but one of them cannot. The presented protocols are also showed to be secure against eavesdropping.

Semi-quantum secret sharing (SQSS) is a branch of quantum cryptography which only requires the dealer to have quantum capabilities, reducing the difficulty of protocol implementation. However, the efficiency of the SQSS protocol still needs to be further studied. In this paper, we propose a semi-quantum secret sharing protocol, whose efficiency can approach 100% as the length of message increases. The protocol is based on single particles to reduce the difficulty of resource preparation. Particle reordering, a simple but effective operation, is used in the protocol to improve efficiency and ensure security. Furthermore, our protocol can share specific secrets while most SQSS protocols could not. We also prove that the protocol is secure against common attacks.

Publisher's Note: Semiquantum secret sharing using entangled states [Phys. Rev. A<b>82</b>, 022303 (2010)