Bidirectional quantum secure communication based on a shared private Bell state
Introduction
Since the pioneering work of Bennett and Brassard [1], much attention has been focused on quantum key distribution (QKD) and many protocols have been put forward, such as Ekert 1991 protocol (Ekert 91) [2], Bennett–Brassard–Mermin 1992 protocol (BBM92) [3], B92 protocol [4] and other protocols [5], [6]. In a communication that is based on QKD, the sender and the receiver firstly share a private key securely, then the sender use it to encrypt secret message into cipher text, this process can be finished by classical cryptographic scheme such as the one-time pad [7]. The cipher text is then sent to the receiver through a classical channel.
Quantum secure direct communication (QSDC) [8], [9], [10], [11], [12], [13], [14] is another branch of quantum cryptography. Different from communication based on QKD, in QSDC, secret message is sent directly to the receiver through quantum channel, and the users do not need to establish a prior secret key, to encrypt and decrypt.
If designed carefully, a QSDC protocol can also attain unconditional security in theory [10], [15], [16]. At the beginning, QSDC can only transport information in a one-way manner (secret message can only be transmitted from A to B). As an improvement to the one-way QSDC, bidirectional QSDC protocol [17], which is also called quantum dialogue, was proposed. A lot of papers [18], [19], [20] then focused on this topic. The character of bidirectional manner is that the users can exchange their secret message simultaneously. However, very recently, Gao et al. [21] pointed out that there exists a kind of insecurity, called information leakage, in the bidirectional QSDC protocol [17]. This insecurity is different from that of the previous subtle attack strategies [22], [23], [24]. As is well known, classical communication is necessary in quantum cryptography, nevertheless it is these public classical communication that make many previous bidirectional quantum communication unsecure (quantum dialogue unsecure).
In this paper, we propose a secure bidirectional quantum communication protocol based on a shared private quantum state. In our protocol, the two legitimate users can exchange their secret securely and the drawback (i.e. information leakage) in Refs. [17], [18], [19] is overcome. Besides, our protocol also has high efficiency.
Section snippets
Bidirectional quantum communication scheme
Before presenting our protocol, let us give a review about the Nguyen’s quantum dialogue protocol [17], which is a typical case of information leakage [21]. In 2004, Nguyen proposed his quantum dialogue protocol, soon after, Man et al. [18] pointed out that this protocol is vulnerable to the intercept-and-resend attack and put forward an improved version. Similar to the Ref. [21], we will focus on information leakage, rather than other subtle attack strategies. Therefore, we do not need to
Security of the protocol
Next, let’s discuss the security of our protocol. In our protocol, EPR pairs act as quantum channel, and the security of our protocol is based on the transmission of sequence , if the sequence is securely transmitted, Eve can only disturb the transmission of sequence and can not steal any encoded information because no one can read the secret message from one particle of an EPR pair. One can see that the transmission of sequence in our scheme is something like that of BBM92 QKD
Conclusion
Perhaps someone will think that our protocol is very similar to QKD in the sense of sharing a private Bell state, so they also think that Alice and Bob can realize bidirectional communication based on QKD & OTP (One-time pad). In a QKD & OTP based bidirectional communication, Alice and Bob first need to share a private key which is the same length as their total secret via QKD; secondly, both sides encrypt their respective secret message into ciphertexts; finally, they declare their ciphertexts
Acknowledgements
This work is supported by the National Natural Science Foundation of China under Grant No. 10547008, the Specialized Research Program of Education Bureau of Shaan Xi Province under Grant Nos. 08JK428 and 08JK434.
References (28)
- et al.
Phys. Lett. A
(2006) Phys. Lett. A
(2004)- C.H. Bennett, G. Brasaard, in: Proceedings of the IEEE International Inference on Computers Systems and Signal...
Phys. Rev. Lett.
(1991)- et al.
Phys. Rev. Lett.
(1992) Phys. Rev. Lett.
(1992)Phys. Rev. Lett.
(2000)- et al.
Phys. Rev. A
(2002) J. Am. Inst. Electron. Eng.
(1926)- et al.
Acta Phys. Pol. A
(2002)