We propose a novel protocol for controlled bidirectional quantum secure communication based on a nonlocal swap gate scheme. Our proposed protocol would be applied to a system in which a controller (supervisor/Charlie) controls the bidirectional communication with quantum information or secret messages between legitimate users (Alice and Bob). In this system, the legitimate users must obtain permission from the controller in order to exchange their respective quantum information or secret messages simultaneously; the controller is unable to obtain any quantum information or secret messages from the decoding process. Moreover, the presence of the controller also avoids the problem of one legitimate user receiving the quantum information or secret message before the other, and then refusing to help the other user decode the quantum information or secret message. Our proposed protocol is aimed at protecting against external and participant attacks on such a system, and the cost of transmitting quantum bits using our protocol is less than that achieved in other studies. Based on the nonlocal swap gate scheme, the legitimate users exchange their quantum information or secret messages without transmission in a public channel, thus protecting against eavesdroppers stealing the secret messages.
We propose a novel protocol for controlled bidirectional quantum secure communication based on a nonlocal swap gate scheme. Our proposed protocol would be applied to a system in which a controller (supervisor/Charlie) controls the bidirectional communication with quantum information or secret messages between legitimate users (Alice and Bob). In this system, the legitimate users must obtain permission from the controller in order to exchange their respective quantum information or secret messages simultaneously; the controller is unable to obtain any quantum information or secret messages from the decoding process. Moreover, the presence of the controller also avoids the problem of one legitimate user receiving the quantum information or secret message before the other, and then refusing to help the other user decode the quantum information or secret message. Our proposed protocol is aimed at protecting against external and participant attacks on such a system, and the cost of transmitting quantum bits using our protocol is less than that achieved in other studies. Based on the nonlocal swap gate scheme, the legitimate users exchange their quantum information or secret messages without transmission in a public channel, thus protecting against eavesdroppers stealing the secret messages.
We present a controlled quantum teleportation protocol. In the protocol, quantum information of an unknown state of a 2-level particle is faithfully transmitted from a sender Alice to a remote receiver Bob via an initially shared triplet of entangled particles under the control of the supervisor Charlie. The distributed entangled particles shared by Alice, Bob and Charlie function as a quantum information channel for faithful transmission. We also propose a controlled and secure direct communication scheme by means of this teleportation. After ensuring the security of the quantum channel, Alice encodes the secret message directly on a sequence of particle states and transmits them to Bob supervised by Charlie using this controlled quantum teleportation. Bob can read out the encoded message directly by the measurement on his qubit. In this scheme, the controlled quantum teleportation transmits Alice's message without revealing any information to a potential eavesdropper. Because there is not a transmission of the qubit carrying the secret message between Alice and Bob in the public channel, it is completely secure for controlled and direct secret communication if perfect quantum channel is used. The special feature of this scheme is that the communication between two sides depends on the agreement of a third side to co-operate.
A controlled bidirectional quantum secure direct communication protocol without information leakage was proposed.In the proposed protocol,two authenticated communication parties,Alice and Bob,were able to securely exchange their secret messages simultaneously under the control of the controller,Charlie.The problem of information leakage was overcome by making full use of the measurement correlation property after entanglement swapping among three Bell states.Moreover,the proposed protocol merely took the Bell state as quantum resource and merely needed the Bell measurement so that it was convenient to implement.Security analysis shows that the proposed protocol can detect not only the active attacks from the outside eavesdropper,but also the dishonest behavior from the controller,Charlie.It can be concluded that the proposed protocol has good security.
Abstract Controlled bidirectional quantum secure direct communication (CBQSDC) is an important research direction in quantum secure direct communication. It can enable two legitimate users to confidentially exchange secret messages only with the permission of the controller. In many practical scenarios, CBQSDC needs to avoid the controller from obtaining useful information on the secret messages. Therefore, in this paper, we introduce the concept of controller independent controlled bidirectional quantum secure direct communication (CICBQSDC) that has a controller to control the communication but restricts the controller to obtain useful information on the secret messages. In other words, we only require the controller of CICBQSDC to cooperate, not to be trusted. In addition, a novel CICBQSDC protocol is constructed. To make CICBQSDC protocols have broad application scenarios, we point out that they need to avoid four security problems: the information leakage problem, the problem of violating simultaneity, the problem of communication not being controlled, and the problem of controllers stealing secret information. Furthermore, we show that the constructed CICBQSDC protocol can avoid the four security problems. Moreover, the unconditional security of the constructed CICBQSDC protocol is demonstrated in the asymptotic scenario.
Abstract This paper presents a groundbreaking protocol for controlled bidirectional quantum secure direct communication based on hyperentangled Bell states, involving two longitudinal momentum and polarization degrees of freedom. In this protocol, the controller Charlie governs bidirectional communication between two legitimate participants. Participants encode their secret messages using 64 unitary operations. However, without Charlie’s permission, specifically without publishing the final measurement results, participants cannot exchange secret messages. Security analysis are conducted to prevent eavesdropper Eve from obtaining users’ secret messages through illegitimate means. Compared with previously proposed controlled bidirectional quantum secure direct communication, the proposed protocol significantly improves transmission efficiency because each pair of photons can transmit 12 bits of classical information. The protocol achieves a remarkable qubit efficiency, reaching up to 85.7%. However, when we don’t take into account the number of qubits consumed by the decoy particles, we can theoretically achieve an efficiency of 200%.
A theoretical scheme for alternative and secure direct communication is proposed. The communication is based on controlled quantum teleportation via state. After insuring the security of the quantum channels (a set of qubits in the states), Alice encodes the secret messages directly on a sequence of particle states and transmits them to Bob supported by Charlie, or to Charlie supported by Bob, using controlled quantum teleportation. Bob or Charlie can read out the encoded messages directly by the measurement on his qubits. In this scheme, the controlled quantum teleportation transmits Alice's message without revealing any information to a potential eavesdropper. Because there is no a transmission of the qubits carrying the secret messages between legitimate parties in the public channel, it is completely secure for direct secret communication if perfect quantum channel is used. We also discuss that when one of the three legitimate parties does not cooperate with others because of some reasons, the remaining two persons can still communicate with each other by entanglement purification. The main feature of this scheme is that the communicate between two sides is alternative but depends on the agreement of the third, and more over, the communication between two sides does not suspend with loss of one of three qubits ( i.e., one of the three legitimate parties does not cooperate with others).
In light of a quantum secure direct communication (QSDC) scheme using entanglement swapping [Chin. Phys. Lett. 22 (2005) 18], by introducing additional local operations for encoding, we propose a bidirectional QSDC (BQSDC) protocol, in which two legitimate users can simultaneously exchange their respective messages. The rule for the users to retrieve his/her partner's messages is derived explicitly in the most general case. Eve's commonly used attack method has been discussed and can be detected with the security checking process.