Quantum secret sharing using weak coherent states

Abstract

Secret sharing allows a trusted party (the dealer) to distribute a secret to a group of players, who can only access the secret cooperatively. Quantum secret sharing (QSS) protocols could provide unconditional security based on fundamental laws in physics. While the general security proof has been established recently in an entanglement-based QSS protocol, the tolerable channel loss is unfortunately rather small. Here we propose a continuous variable QSS protocol using conventional laser sources and homodyne detectors. In this protocol, a Gaussian-modulated coherent state (GMCS) prepared by one player passes through the secure stations of the other players sequentially, and each of the other players injects a locally prepared, independent GMCS into the circulating optical mode. Finally, the dealer measures both the amplitude and the phase quadratures of the receiving optical mode using double homodyne detectors. Collectively, the players can use their encoded random numbers to estimate the measurement results of the dealer and further generate a shared key. We prove the unconditional security of the proposed protocol against both eavesdroppers and dishonest players in the presence of high channel loss, and discuss various practical issues. a

Improving Continuous Variable Quantum Secret Sharing with Weak Coherent States

“…Enlightened by the characteristics of the GMCS-involved quantum key distribution (QKD) [19] and the topological structure of the (n, n)-threshold scheme using weak coherent states [24], we propose an improved (t, n) threshold scheme for the practical CVQSS.…”

“…Because the secure key of CVQSS ought to secure against any group of t − 1 participants, the dealer needs to select the smallest one among secure key rates of legitimate participants and the dealer. The secure key rate of the GMCS-based QKD can be calculated between the dealer and a selected participant while other t − 1 legitimate participants are dishonest [24,34]. In order to show the performance of the CVQSS protocol, we execute simulations using concrete parameters and analyze the results in the next section.…”

“…After that, the (2,3) threshold scheme was designed using entangled system [16]. Thereafter, the (n, n)-threshold protocol was dished with weak coherent state [24]. However, most of QSS protocols are based on squeezed states which are difficult to prepare in the laboratory, compared with coherent states.…”

Differential phase shift quantum secret sharing using a twin field

“…Nevertheless, difficulties in preparing and transmitting GHZ states constrains the secret key rate and stability of QSS systems, making it far from practical implementation. Therefore, several protocols in the prepare-and-measure scenario were proposed to circumvent preparations of multipartite entangled states, such as protocols using post-selected multipartite entanglement state [15], Bell states [16,17], continuous variable [18,19], single-qubit scheme [20][21][22][23], d-level scheme [24,25] and differential phase shift scheme [26]. Unfortunately, a majority of prepare-and-measure protocols [20][21][22][23][24][25][26] is vulnerable to the Trojan horse attacks [27,28].…”

Passive state preparation in continuous-variable quantum key distribution

“…More recently, this passive state preparation scheme has been extended to measurement-device-independent CV QKD [23]. It could also be applied in other CV quantum communication protocols, such as quantum secret sharing [24] and quantum digital signature [25].…”