Multiparty-controlled quantum secure direct communication
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TOMS, MOLECULES, OPTICS
Multiparty-Controlled Quantum Secure Direct Communication1 X.-M. Xiu, L. Dong, Y.-J. Gao, and F. Chi Physics Department, Bohai University, Jinzhou, 121000 People’s Republic of China e-mail: [email protected] Received July 12, 2007
Abstract—A theoretical scheme of a multiparty-controlled quantum secure direct communication is proposed. The supervisor prepares a communication network with Einstein–Podolsky–Rosen pairs and auxiliary particles. After passing a security test of the communication network, a supervisor tells the users the network is secure and they can communicate. If the controllers allow the communicators to communicate, the controllers should perform measurements and inform the communicators of the outcomes. The communicators then begin to communicate after they perform a security test of the quantum channel and verify that it is secure. The recipient can decrypt the secret message in a classical message from the sender depending on the protocol. Any two users in the network can communicate through the above processes under the control of the supervisor and the controllers. PACS numbers: 03.67.Hk, 03.67.Dd, 03.65.Ud DOI: 10.1134/S1063776107120047 1
1. INTRODUCTION
Cryptography [1] is an important branch of quantum information theory, which enables two communicators to communicate in privacy. Using the characteristics of quantum mechanics, for example, quantum entanglement, secret information can be securely transmitted between two users. Quantum key distribution (QKD) is a process whereby two legitimate users first establish a shared secret key by means of the transmission of a classical message and then use this key to encrypt (decrypt) a secret message. Since the first QKD scheme proposed in 1984 [2], many QKD schemes have been presented [3–8]. In 2002, a quantum secure direct communication (QSDC) scheme was proposed in [9], which permits messages to be communicated directly without first establishing a random key to encrypt them as QKD schemes do. Subsequently, the so-called “ping-pong protocol” was proposed in [10], allowing the encoded bit to be decoded instantaneously in each respective round of transmissions. However, it is insecure in a noisy quantum channel, as indicated in [11, 12]. Also, the ping-pong protocol can be attacked without eavesdropping [13, 14]. The ping-pong protocol was modified in [15] for transmitting a secret message with a single photon in a mixed state. A two-step QSDC protocol using blocks of Einstein–Podolsky–Rosen (EPR) pairs was proposed in [16], and a QSDC scheme with a quantum one-time pad using single photons in [17] was developed to enhance security of the communication. To date, many studies have been focused on QSDC schemes [9–24]. As a matter of fact, in the above schemes, the secret information to be sent can be read by the recipient only 1 The
text was submitted by the authors in English.
after the sender completes the transmission of classical information for each qubit. It is necessary for the sender to send the qubits carryin
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